* [PATCH v7 00/10] can: bcm: collected fixes - final2 :-D
@ 2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
0 siblings, 0 replies; 29+ messages in thread
From: Oliver Hartkopp @ 2026-07-08 15:21 UTC (permalink / raw)
To: linux-can
Cc: Oliver Hartkopp, Marc Kleine-Budde, Lee Jones, Feng Xue, Ginger,
syzbot+75e5e4ae00c3b4bb544e, sashiko-reviews, sashiko-bot
Hi Marc,
as there were different patches flying arround to fix CAN_BCM issues and
AI assisted stuff pop's up again and again, I've created this collection
to be applied.
The patch series fixes ALL issues reported by ALL kind of AI bots involved
and the fixes were assisted by claude code and later rephrased and shortened
by myself.
Inserted a new patch 9 that addresses a late sashiko-bot report fixing some
stale rx/tx ops behaviour after device removal.
So the potential new AI reports on this patch set report problems that are
solved later in the series. This can not be resolved.
Best regards,
Oliver
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
Changes in v7:
- patch 9: new: fix stale rx/tx ops after device removal reported by
sashiko-bot: https://lore.kernel.org/linux-can/20260708094536.DDF821F00A3A@smtp.kernel.org/
- patch 10: formerly patch 9 as new patch 8 & 9 belong together
- Link to v6: https://patch.msgid.link/20260708-bcm_fixes-v6-0-80710a2bc398@hartkopp.net
Changes in v6:
- patch 1: added Tested-by: tags
- patch 3: changed commit message and comment regarding a wrong claim
about synchronous delivery from dev_queue_xmit() as remarked by
https://netdev-ai.bots.linux.dev/ai-review.html?id=6105ebab-87ef-43db-a085-7c190b9f119f
- patch 4: rebased patch 3 comment
- patch 9: new: fix data race on rx_stamp/rx_ifindex in bcm_rx_handler()
reported by sashiko-bot: https://lore.kernel.org/linux-can/20260707145135.5BC831F00A3A@smtp.kernel.org/
- Link to v5: https://patch.msgid.link/20260707-bcm_fixes-v5-0-c3c74f8d8ff7@hartkopp.net
Changes in v5:
- patch 6: changed comment for bcm_op::bcm_tx_lock (mkl)
- patch 8: new: add missing device refcount for CAN filter removal
- Link to v4: https://patch.msgid.link/20260707-bcm_fixes-v4-0-aa87b8b9d33f@hartkopp.net
Changes in v4:
- incorporated more sashiko-bot concerns from v3
- patch 3: omit hrtimer_forward with zero interval
- patch 4: put bcm_update_stats() under bcm_rx_update_lock
- Link to v3: https://patch.msgid.link/20260707-bcm_fixes-v3-0-84600ca6d889@hartkopp.net
Changes in v3:
- incorporated more sashiko-bot concerns from v2
- patch 3: make snapshot of currframe
- patch 6: add error patch for memcpy_from_msg()
- patch 7: new RTR-reply validation in bcm_rx_setup() from bcm_tx_setup()
- Link to v2: https://patch.msgid.link/20260707-bcm_fixes-v2-0-96620c534b75@hartkopp.net
Changes in v2:
- incorporated all sashiko-bot concerns from v1
- Link to v1: https://patch.msgid.link/20260612-bcm_fixes-v1-0-ca2fa07ee70f@hartkopp.net
---
Lee Jones (1):
can: bcm: defer rx_op deallocation to workqueue to fix thrtimer UAF
Oliver Hartkopp (9):
can: bcm: fix lockless bound/ifindex race and silent RX_SETUP failure
can: bcm: add locking when updating filter and timer values
can: bcm: fix CAN frame rx/tx statistics
can: bcm: add missing rcu list annotations and operations
can: bcm: extend bcm_tx_lock usage for data and timer updates
can: bcm: validate frame length in bcm_rx_setup() for RTR replies
can: bcm: add missing device refcount for CAN filter removal
can: bcm: fix stale rx/tx ops after device removal
can: bcm: fix data race on rx_stamp/rx_ifindex in bcm_rx_handler()
net/can/bcm.c | 525 +++++++++++++++++++++++++++++++++++++++++++---------------
1 file changed, 390 insertions(+), 135 deletions(-)
---
base-commit: 0e35b9b6ec0ffcc5e23cbdec09f5c622ad532b53
change-id: 20260612-bcm_fixes-84fb4aa93ac2
Best regards,
--
Oliver Hartkopp <socketcan@hartkopp.net>
^ permalink raw reply [flat|nested] 29+ messages in thread
* [PATCH v7 00/10] can: bcm: collected fixes - final2 :-D
@ 2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
0 siblings, 0 replies; 29+ messages in thread
From: Oliver Hartkopp via B4 Relay @ 2026-07-08 15:21 UTC (permalink / raw)
To: linux-can
Cc: Oliver Hartkopp, Marc Kleine-Budde, Lee Jones, Feng Xue, Ginger,
syzbot+75e5e4ae00c3b4bb544e, sashiko-reviews, sashiko-bot
Hi Marc,
as there were different patches flying arround to fix CAN_BCM issues and
AI assisted stuff pop's up again and again, I've created this collection
to be applied.
The patch series fixes ALL issues reported by ALL kind of AI bots involved
and the fixes were assisted by claude code and later rephrased and shortened
by myself.
Inserted a new patch 9 that addresses a late sashiko-bot report fixing some
stale rx/tx ops behaviour after device removal.
So the potential new AI reports on this patch set report problems that are
solved later in the series. This can not be resolved.
Best regards,
Oliver
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
Changes in v7:
- patch 9: new: fix stale rx/tx ops after device removal reported by
sashiko-bot: https://lore.kernel.org/linux-can/20260708094536.DDF821F00A3A@smtp.kernel.org/
- patch 10: formerly patch 9 as new patch 8 & 9 belong together
- Link to v6: https://patch.msgid.link/20260708-bcm_fixes-v6-0-80710a2bc398@hartkopp.net
Changes in v6:
- patch 1: added Tested-by: tags
- patch 3: changed commit message and comment regarding a wrong claim
about synchronous delivery from dev_queue_xmit() as remarked by
https://netdev-ai.bots.linux.dev/ai-review.html?id=6105ebab-87ef-43db-a085-7c190b9f119f
- patch 4: rebased patch 3 comment
- patch 9: new: fix data race on rx_stamp/rx_ifindex in bcm_rx_handler()
reported by sashiko-bot: https://lore.kernel.org/linux-can/20260707145135.5BC831F00A3A@smtp.kernel.org/
- Link to v5: https://patch.msgid.link/20260707-bcm_fixes-v5-0-c3c74f8d8ff7@hartkopp.net
Changes in v5:
- patch 6: changed comment for bcm_op::bcm_tx_lock (mkl)
- patch 8: new: add missing device refcount for CAN filter removal
- Link to v4: https://patch.msgid.link/20260707-bcm_fixes-v4-0-aa87b8b9d33f@hartkopp.net
Changes in v4:
- incorporated more sashiko-bot concerns from v3
- patch 3: omit hrtimer_forward with zero interval
- patch 4: put bcm_update_stats() under bcm_rx_update_lock
- Link to v3: https://patch.msgid.link/20260707-bcm_fixes-v3-0-84600ca6d889@hartkopp.net
Changes in v3:
- incorporated more sashiko-bot concerns from v2
- patch 3: make snapshot of currframe
- patch 6: add error patch for memcpy_from_msg()
- patch 7: new RTR-reply validation in bcm_rx_setup() from bcm_tx_setup()
- Link to v2: https://patch.msgid.link/20260707-bcm_fixes-v2-0-96620c534b75@hartkopp.net
Changes in v2:
- incorporated all sashiko-bot concerns from v1
- Link to v1: https://patch.msgid.link/20260612-bcm_fixes-v1-0-ca2fa07ee70f@hartkopp.net
---
Lee Jones (1):
can: bcm: defer rx_op deallocation to workqueue to fix thrtimer UAF
Oliver Hartkopp (9):
can: bcm: fix lockless bound/ifindex race and silent RX_SETUP failure
can: bcm: add locking when updating filter and timer values
can: bcm: fix CAN frame rx/tx statistics
can: bcm: add missing rcu list annotations and operations
can: bcm: extend bcm_tx_lock usage for data and timer updates
can: bcm: validate frame length in bcm_rx_setup() for RTR replies
can: bcm: add missing device refcount for CAN filter removal
can: bcm: fix stale rx/tx ops after device removal
can: bcm: fix data race on rx_stamp/rx_ifindex in bcm_rx_handler()
net/can/bcm.c | 525 +++++++++++++++++++++++++++++++++++++++++++---------------
1 file changed, 390 insertions(+), 135 deletions(-)
---
base-commit: 0e35b9b6ec0ffcc5e23cbdec09f5c622ad532b53
change-id: 20260612-bcm_fixes-84fb4aa93ac2
Best regards,
--
Oliver Hartkopp <socketcan@hartkopp.net>
^ permalink raw reply [flat|nested] 29+ messages in thread
* [PATCH v7 01/10] can: bcm: defer rx_op deallocation to workqueue to fix thrtimer UAF
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
@ 2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
-1 siblings, 0 replies; 29+ messages in thread
From: Oliver Hartkopp @ 2026-07-08 15:21 UTC (permalink / raw)
To: linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde, Lee Jones, Feng Xue
From: Lee Jones <lee@kernel.org>
Commit f1b4e32aca08 ("can: bcm: use call_rcu() instead of costly
synchronize_rcu()") replaced synchronize_rcu() in bcm_delete_rx_op()
with call_rcu() and introduced the RX_NO_AUTOTIMER flag.
However, this flag check was omitted for thrtimer in the packet rx
fast-path. During BCM RX operation teardown, a concurrent RCU reader
(bcm_rx_handler) can race and re-arm thrtimer via
bcm_rx_update_and_send() after call_rcu() has been scheduled. Once
the RCU grace period elapses, bcm_op is freed. The subsequently
firing thrtimer then dereferences the deallocated op, causing a UAF.
Adding flag checks to the rx fast-path (bcm_rx_update_and_send) does not
fully close the TOCTOU race and introduces latency for every CAN frame.
Conversely, calling hrtimer_cancel() directly inside the RCU callback
(softirq context) is fatal as hrtimer_cancel() can sleep, triggering
a "scheduling while atomic" panic.
Resolve this by deferring the timer cancellation and memory free to a
dedicated unbound workqueue (bcm_wq). The RCU callback now queues a
work item to bcm_wq, which safely cancels both timers and deallocates
memory in sleepable process context. A dedicated workqueue is used to
prevent system-wide WQ saturation and is cleanly flushed/destroyed
on module unload to avoid rmmod page faults.
Since the deferred work can now outlive the calling context by an
unbounded amount, also take a reference on op->sk when it is assigned
and drop it only once the deferred work has cancelled both timers, so a
socket can no longer be freed out from under a still-armed timer whose
callback (bcm_send_to_user()) dereferences op->sk.
Fixes: f1b4e32aca08 ("can: bcm: use call_rcu() instead of costly synchronize_rcu()")
Tested-by: Feng Xue <feng.xue@outlook.com>
Tested-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Lee Jones <lee@kernel.org>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
net/can/bcm.c | 37 ++++++++++++++++++++++++++++++++++---
1 file changed, 34 insertions(+), 3 deletions(-)
diff --git a/net/can/bcm.c b/net/can/bcm.c
index a4bef2c48a55..bdf53241bd7b 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -56,10 +56,11 @@
#include <linux/can.h>
#include <linux/can/core.h>
#include <linux/can/skb.h>
#include <linux/can/bcm.h>
#include <linux/slab.h>
+#include <linux/workqueue.h>
#include <linux/spinlock.h>
#include <net/can.h>
#include <net/sock.h>
#include <net/net_namespace.h>
@@ -90,10 +91,12 @@ MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Oliver Hartkopp <oliver.hartkopp@volkswagen.de>");
MODULE_ALIAS("can-proto-2");
#define BCM_MIN_NAMELEN CAN_REQUIRED_SIZE(struct sockaddr_can, can_ifindex)
+static struct workqueue_struct *bcm_wq;
+
/*
* easy access to the first 64 bit of can(fd)_frame payload. cp->data is
* 64 bit aligned so the offset has to be multiples of 8 which is ensured
* by the only callers in bcm_rx_cmp_to_index() bcm_rx_handler().
*/
@@ -103,10 +106,11 @@ static inline u64 get_u64(const struct canfd_frame *cp, int offset)
}
struct bcm_op {
struct list_head list;
struct rcu_head rcu;
+ struct work_struct work;
int ifindex;
canid_t can_id;
u32 flags;
unsigned long frames_abs, frames_filtered;
struct bcm_timeval ival1, ival2;
@@ -791,23 +795,40 @@ static struct bcm_op *bcm_find_op(struct list_head *ops,
}
return NULL;
}
-static void bcm_free_op_rcu(struct rcu_head *rcu_head)
+static void bcm_free_op_work(struct work_struct *work)
{
- struct bcm_op *op = container_of(rcu_head, struct bcm_op, rcu);
+ struct bcm_op *op = container_of(work, struct bcm_op, work);
+
+ hrtimer_cancel(&op->timer);
+ hrtimer_cancel(&op->thrtimer);
if ((op->frames) && (op->frames != &op->sframe))
kfree(op->frames);
if ((op->last_frames) && (op->last_frames != &op->last_sframe))
kfree(op->last_frames);
+ /* the last possible access to op->timer/op->thrtimer has now
+ * happened above via hrtimer_cancel() - op->sk is no longer
+ * needed by any pending timer callback, so drop our reference
+ */
+ sock_put(op->sk);
+
kfree(op);
}
+static void bcm_free_op_rcu(struct rcu_head *rcu_head)
+{
+ struct bcm_op *op = container_of(rcu_head, struct bcm_op, rcu);
+
+ INIT_WORK(&op->work, bcm_free_op_work);
+ queue_work(bcm_wq, &op->work);
+}
+
static void bcm_remove_op(struct bcm_op *op)
{
hrtimer_cancel(&op->timer);
hrtimer_cancel(&op->thrtimer);
@@ -1058,10 +1079,11 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
/* tx_ops never compare with previous received messages */
op->last_frames = NULL;
/* bcm_can_tx / bcm_tx_timeout_handler needs this */
op->sk = sk;
+ sock_hold(sk);
op->ifindex = ifindex;
/* initialize uninitialized (kzalloc) structure */
hrtimer_setup(&op->timer, bcm_tx_timeout_handler, CLOCK_MONOTONIC,
HRTIMER_MODE_REL_SOFT);
@@ -1219,10 +1241,11 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
}
}
/* bcm_can_tx / bcm_tx_timeout_handler needs this */
op->sk = sk;
+ sock_hold(sk);
op->ifindex = ifindex;
/* ifindex for timeout events w/o previous frame reception */
op->rx_ifindex = ifindex;
@@ -1837,15 +1860,19 @@ static struct notifier_block canbcm_notifier = {
static int __init bcm_module_init(void)
{
int err;
+ bcm_wq = alloc_workqueue("can-bcm-wq", WQ_UNBOUND, 0);
+ if (!bcm_wq)
+ return -ENOMEM;
+
pr_info("can: broadcast manager protocol\n");
err = register_pernet_subsys(&canbcm_pernet_ops);
if (err)
- return err;
+ goto register_pernet_failed;
err = register_netdevice_notifier(&canbcm_notifier);
if (err)
goto register_notifier_failed;
@@ -1859,17 +1886,21 @@ static int __init bcm_module_init(void)
register_proto_failed:
unregister_netdevice_notifier(&canbcm_notifier);
register_notifier_failed:
unregister_pernet_subsys(&canbcm_pernet_ops);
+register_pernet_failed:
+ destroy_workqueue(bcm_wq);
return err;
}
static void __exit bcm_module_exit(void)
{
can_proto_unregister(&bcm_can_proto);
unregister_netdevice_notifier(&canbcm_notifier);
unregister_pernet_subsys(&canbcm_pernet_ops);
+ rcu_barrier();
+ destroy_workqueue(bcm_wq);
}
module_init(bcm_module_init);
module_exit(bcm_module_exit);
--
2.53.0
^ permalink raw reply related [flat|nested] 29+ messages in thread
* [PATCH v7 01/10] can: bcm: defer rx_op deallocation to workqueue to fix thrtimer UAF
@ 2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
0 siblings, 0 replies; 29+ messages in thread
From: Oliver Hartkopp via B4 Relay @ 2026-07-08 15:21 UTC (permalink / raw)
To: linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde, Lee Jones, Feng Xue
From: Lee Jones <lee@kernel.org>
Commit f1b4e32aca08 ("can: bcm: use call_rcu() instead of costly
synchronize_rcu()") replaced synchronize_rcu() in bcm_delete_rx_op()
with call_rcu() and introduced the RX_NO_AUTOTIMER flag.
However, this flag check was omitted for thrtimer in the packet rx
fast-path. During BCM RX operation teardown, a concurrent RCU reader
(bcm_rx_handler) can race and re-arm thrtimer via
bcm_rx_update_and_send() after call_rcu() has been scheduled. Once
the RCU grace period elapses, bcm_op is freed. The subsequently
firing thrtimer then dereferences the deallocated op, causing a UAF.
Adding flag checks to the rx fast-path (bcm_rx_update_and_send) does not
fully close the TOCTOU race and introduces latency for every CAN frame.
Conversely, calling hrtimer_cancel() directly inside the RCU callback
(softirq context) is fatal as hrtimer_cancel() can sleep, triggering
a "scheduling while atomic" panic.
Resolve this by deferring the timer cancellation and memory free to a
dedicated unbound workqueue (bcm_wq). The RCU callback now queues a
work item to bcm_wq, which safely cancels both timers and deallocates
memory in sleepable process context. A dedicated workqueue is used to
prevent system-wide WQ saturation and is cleanly flushed/destroyed
on module unload to avoid rmmod page faults.
Since the deferred work can now outlive the calling context by an
unbounded amount, also take a reference on op->sk when it is assigned
and drop it only once the deferred work has cancelled both timers, so a
socket can no longer be freed out from under a still-armed timer whose
callback (bcm_send_to_user()) dereferences op->sk.
Fixes: f1b4e32aca08 ("can: bcm: use call_rcu() instead of costly synchronize_rcu()")
Tested-by: Feng Xue <feng.xue@outlook.com>
Tested-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Lee Jones <lee@kernel.org>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
net/can/bcm.c | 37 ++++++++++++++++++++++++++++++++++---
1 file changed, 34 insertions(+), 3 deletions(-)
diff --git a/net/can/bcm.c b/net/can/bcm.c
index a4bef2c48a55..bdf53241bd7b 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -56,10 +56,11 @@
#include <linux/can.h>
#include <linux/can/core.h>
#include <linux/can/skb.h>
#include <linux/can/bcm.h>
#include <linux/slab.h>
+#include <linux/workqueue.h>
#include <linux/spinlock.h>
#include <net/can.h>
#include <net/sock.h>
#include <net/net_namespace.h>
@@ -90,10 +91,12 @@ MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Oliver Hartkopp <oliver.hartkopp@volkswagen.de>");
MODULE_ALIAS("can-proto-2");
#define BCM_MIN_NAMELEN CAN_REQUIRED_SIZE(struct sockaddr_can, can_ifindex)
+static struct workqueue_struct *bcm_wq;
+
/*
* easy access to the first 64 bit of can(fd)_frame payload. cp->data is
* 64 bit aligned so the offset has to be multiples of 8 which is ensured
* by the only callers in bcm_rx_cmp_to_index() bcm_rx_handler().
*/
@@ -103,10 +106,11 @@ static inline u64 get_u64(const struct canfd_frame *cp, int offset)
}
struct bcm_op {
struct list_head list;
struct rcu_head rcu;
+ struct work_struct work;
int ifindex;
canid_t can_id;
u32 flags;
unsigned long frames_abs, frames_filtered;
struct bcm_timeval ival1, ival2;
@@ -791,23 +795,40 @@ static struct bcm_op *bcm_find_op(struct list_head *ops,
}
return NULL;
}
-static void bcm_free_op_rcu(struct rcu_head *rcu_head)
+static void bcm_free_op_work(struct work_struct *work)
{
- struct bcm_op *op = container_of(rcu_head, struct bcm_op, rcu);
+ struct bcm_op *op = container_of(work, struct bcm_op, work);
+
+ hrtimer_cancel(&op->timer);
+ hrtimer_cancel(&op->thrtimer);
if ((op->frames) && (op->frames != &op->sframe))
kfree(op->frames);
if ((op->last_frames) && (op->last_frames != &op->last_sframe))
kfree(op->last_frames);
+ /* the last possible access to op->timer/op->thrtimer has now
+ * happened above via hrtimer_cancel() - op->sk is no longer
+ * needed by any pending timer callback, so drop our reference
+ */
+ sock_put(op->sk);
+
kfree(op);
}
+static void bcm_free_op_rcu(struct rcu_head *rcu_head)
+{
+ struct bcm_op *op = container_of(rcu_head, struct bcm_op, rcu);
+
+ INIT_WORK(&op->work, bcm_free_op_work);
+ queue_work(bcm_wq, &op->work);
+}
+
static void bcm_remove_op(struct bcm_op *op)
{
hrtimer_cancel(&op->timer);
hrtimer_cancel(&op->thrtimer);
@@ -1058,10 +1079,11 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
/* tx_ops never compare with previous received messages */
op->last_frames = NULL;
/* bcm_can_tx / bcm_tx_timeout_handler needs this */
op->sk = sk;
+ sock_hold(sk);
op->ifindex = ifindex;
/* initialize uninitialized (kzalloc) structure */
hrtimer_setup(&op->timer, bcm_tx_timeout_handler, CLOCK_MONOTONIC,
HRTIMER_MODE_REL_SOFT);
@@ -1219,10 +1241,11 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
}
}
/* bcm_can_tx / bcm_tx_timeout_handler needs this */
op->sk = sk;
+ sock_hold(sk);
op->ifindex = ifindex;
/* ifindex for timeout events w/o previous frame reception */
op->rx_ifindex = ifindex;
@@ -1837,15 +1860,19 @@ static struct notifier_block canbcm_notifier = {
static int __init bcm_module_init(void)
{
int err;
+ bcm_wq = alloc_workqueue("can-bcm-wq", WQ_UNBOUND, 0);
+ if (!bcm_wq)
+ return -ENOMEM;
+
pr_info("can: broadcast manager protocol\n");
err = register_pernet_subsys(&canbcm_pernet_ops);
if (err)
- return err;
+ goto register_pernet_failed;
err = register_netdevice_notifier(&canbcm_notifier);
if (err)
goto register_notifier_failed;
@@ -1859,17 +1886,21 @@ static int __init bcm_module_init(void)
register_proto_failed:
unregister_netdevice_notifier(&canbcm_notifier);
register_notifier_failed:
unregister_pernet_subsys(&canbcm_pernet_ops);
+register_pernet_failed:
+ destroy_workqueue(bcm_wq);
return err;
}
static void __exit bcm_module_exit(void)
{
can_proto_unregister(&bcm_can_proto);
unregister_netdevice_notifier(&canbcm_notifier);
unregister_pernet_subsys(&canbcm_pernet_ops);
+ rcu_barrier();
+ destroy_workqueue(bcm_wq);
}
module_init(bcm_module_init);
module_exit(bcm_module_exit);
--
2.53.0
^ permalink raw reply related [flat|nested] 29+ messages in thread
* [PATCH v7 02/10] can: bcm: fix lockless bound/ifindex race and silent RX_SETUP failure
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
@ 2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
-1 siblings, 0 replies; 29+ messages in thread
From: Oliver Hartkopp @ 2026-07-08 15:21 UTC (permalink / raw)
To: linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde, Ginger
bcm_sendmsg() reads bo->ifindex and checks bo->bound before taking
lock_sock(), while bcm_notify(), bcm_connect() and bcm_release() all
mutate both fields under that same lock. Because the lockless reads
and the locked writes are unordered with respect to each other, a
racing bcm_notify() (device unregister) or bcm_connect() (concurrent
bind on another thread sharing the socket) can make bcm_sendmsg()
observe an inconsistent combination, e.g. a stale bound=1 together
with the now-cleared ifindex=0, silently turning a socket bound to a
specific CAN interface into one that also matches "any" interface.
Keep the lockless bo->bound check purely as a fast-path reject, and
move the ifindex read (and a bo->bound re-check) into the locked
section, where every writer already serializes. This removes the
possibility of observing the two fields torn against each other,
rather than trying to fix it with more READ_ONCE()/WRITE_ONCE() pairs
on two independently updated fields. Annotate the now-purely-lockless
bo->bound accesses consistently across all its write sites.
Also fix bcm_rx_setup() silently returning success when the target
device disappears concurrently instead of reporting -ENODEV, so a
broken RX op is no longer left registered as if it had succeeded.
Reported-by: Ginger <ginger.jzllee@gmail.com>
Closes: https://lore.kernel.org/linux-can/CAGp+u1aBK8QVjsvAxM2Ldzep4rEbsP9x_pV3At4g=h1kVEtyhA@mail.gmail.com/
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
net/can/bcm.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++-------------
1 file changed, 51 insertions(+), 14 deletions(-)
diff --git a/net/can/bcm.c b/net/can/bcm.c
index bdf53241bd7b..b612135b017d 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -1321,10 +1321,15 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
bcm_rx_handler, op,
"bcm", sk);
op->rx_reg_dev = dev;
dev_put(dev);
+ } else {
+ /* the requested device is gone - do not
+ * silently succeed without registering
+ */
+ err = -ENODEV;
}
} else
err = can_rx_register(sock_net(sk), NULL, op->can_id,
REGMASK(op->can_id),
@@ -1394,16 +1399,17 @@ static int bcm_tx_send(struct msghdr *msg, int ifindex, struct sock *sk,
*/
static int bcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
{
struct sock *sk = sock->sk;
struct bcm_sock *bo = bcm_sk(sk);
- int ifindex = bo->ifindex; /* default ifindex for this bcm_op */
+ int ifindex;
struct bcm_msg_head msg_head;
int cfsiz;
int ret; /* read bytes or error codes as return value */
- if (!bo->bound)
+ /* Lockless fast-path check for bound socket */
+ if (!READ_ONCE(bo->bound))
return -ENOTCONN;
/* check for valid message length from userspace */
if (size < MHSIZ)
return -EINVAL;
@@ -1415,43 +1421,65 @@ static int bcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
cfsiz = CFSIZ(msg_head.flags);
if ((size - MHSIZ) % cfsiz)
return -EINVAL;
+ lock_sock(sk);
+
+ /* Re-validate under the socket lock: a concurrent bcm_notify()
+ * may have unbound this socket (device removal) after the
+ * lockless fast-path check above. bo->ifindex is only ever
+ * mutated under lock_sock(), so reading it here - instead of
+ * before taking the lock - guarantees it can't be observed
+ * torn against bo->bound.
+ */
+ if (!bo->bound) {
+ ret = -ENOTCONN;
+ goto out_release;
+ }
+
+ /* default ifindex for this bcm_op */
+ ifindex = bo->ifindex;
+
/* check for alternative ifindex for this bcm_op */
if (!ifindex && msg->msg_name) {
/* no bound device as default => check msg_name */
DECLARE_SOCKADDR(struct sockaddr_can *, addr, msg->msg_name);
- if (msg->msg_namelen < BCM_MIN_NAMELEN)
- return -EINVAL;
+ if (msg->msg_namelen < BCM_MIN_NAMELEN) {
+ ret = -EINVAL;
+ goto out_release;
+ }
- if (addr->can_family != AF_CAN)
- return -EINVAL;
+ if (addr->can_family != AF_CAN) {
+ ret = -EINVAL;
+ goto out_release;
+ }
/* ifindex from sendto() */
ifindex = addr->can_ifindex;
if (ifindex) {
struct net_device *dev;
dev = dev_get_by_index(sock_net(sk), ifindex);
- if (!dev)
- return -ENODEV;
+ if (!dev) {
+ ret = -ENODEV;
+ goto out_release;
+ }
if (dev->type != ARPHRD_CAN) {
dev_put(dev);
- return -ENODEV;
+ ret = -ENODEV;
+ goto out_release;
}
dev_put(dev);
}
}
- lock_sock(sk);
-
switch (msg_head.opcode) {
case TX_SETUP:
ret = bcm_tx_setup(&msg_head, msg, ifindex, sk);
break;
@@ -1497,10 +1525,11 @@ static int bcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
default:
ret = -EINVAL;
break;
}
+out_release:
release_sock(sk);
return ret;
}
@@ -1533,11 +1562,16 @@ static void bcm_notify(struct bcm_sock *bo, unsigned long msg,
if (sock_net(sk)->can.bcmproc_dir && bo->bcm_proc_read) {
remove_proc_entry(bo->procname, sock_net(sk)->can.bcmproc_dir);
bo->bcm_proc_read = NULL;
}
#endif
- bo->bound = 0;
+ /* Paired with the lockless fast-path check in
+ * bcm_sendmsg(); bo->ifindex itself is only ever
+ * accessed under lock_sock() so it needs no
+ * annotation.
+ */
+ WRITE_ONCE(bo->bound, 0);
bo->ifindex = 0;
notify_enodev = 1;
}
release_sock(sk);
@@ -1674,11 +1708,11 @@ static int bcm_release(struct socket *sock)
list_for_each_entry_safe(op, next, &bo->rx_ops, list)
bcm_remove_op(op);
/* remove device reference */
if (bo->bound) {
- bo->bound = 0;
+ WRITE_ONCE(bo->bound, 0);
bo->ifindex = 0;
}
sock_orphan(sk);
sock->sk = NULL;
@@ -1744,11 +1778,14 @@ static int bcm_connect(struct socket *sock, struct sockaddr_unsized *uaddr, int
goto fail;
}
}
#endif /* CONFIG_PROC_FS */
- bo->bound = 1;
+ /* bo->ifindex above is fully assigned before this point; pairs
+ * with the lockless fast-path check in bcm_sendmsg()
+ */
+ WRITE_ONCE(bo->bound, 1);
fail:
release_sock(sk);
return ret;
--
2.53.0
^ permalink raw reply related [flat|nested] 29+ messages in thread
* [PATCH v7 02/10] can: bcm: fix lockless bound/ifindex race and silent RX_SETUP failure
@ 2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
0 siblings, 0 replies; 29+ messages in thread
From: Oliver Hartkopp via B4 Relay @ 2026-07-08 15:21 UTC (permalink / raw)
To: linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde, Ginger
From: Oliver Hartkopp <socketcan@hartkopp.net>
bcm_sendmsg() reads bo->ifindex and checks bo->bound before taking
lock_sock(), while bcm_notify(), bcm_connect() and bcm_release() all
mutate both fields under that same lock. Because the lockless reads
and the locked writes are unordered with respect to each other, a
racing bcm_notify() (device unregister) or bcm_connect() (concurrent
bind on another thread sharing the socket) can make bcm_sendmsg()
observe an inconsistent combination, e.g. a stale bound=1 together
with the now-cleared ifindex=0, silently turning a socket bound to a
specific CAN interface into one that also matches "any" interface.
Keep the lockless bo->bound check purely as a fast-path reject, and
move the ifindex read (and a bo->bound re-check) into the locked
section, where every writer already serializes. This removes the
possibility of observing the two fields torn against each other,
rather than trying to fix it with more READ_ONCE()/WRITE_ONCE() pairs
on two independently updated fields. Annotate the now-purely-lockless
bo->bound accesses consistently across all its write sites.
Also fix bcm_rx_setup() silently returning success when the target
device disappears concurrently instead of reporting -ENODEV, so a
broken RX op is no longer left registered as if it had succeeded.
Reported-by: Ginger <ginger.jzllee@gmail.com>
Closes: https://lore.kernel.org/linux-can/CAGp+u1aBK8QVjsvAxM2Ldzep4rEbsP9x_pV3At4g=h1kVEtyhA@mail.gmail.com/
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
net/can/bcm.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++-------------
1 file changed, 51 insertions(+), 14 deletions(-)
diff --git a/net/can/bcm.c b/net/can/bcm.c
index bdf53241bd7b..b612135b017d 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -1321,10 +1321,15 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
bcm_rx_handler, op,
"bcm", sk);
op->rx_reg_dev = dev;
dev_put(dev);
+ } else {
+ /* the requested device is gone - do not
+ * silently succeed without registering
+ */
+ err = -ENODEV;
}
} else
err = can_rx_register(sock_net(sk), NULL, op->can_id,
REGMASK(op->can_id),
@@ -1394,16 +1399,17 @@ static int bcm_tx_send(struct msghdr *msg, int ifindex, struct sock *sk,
*/
static int bcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
{
struct sock *sk = sock->sk;
struct bcm_sock *bo = bcm_sk(sk);
- int ifindex = bo->ifindex; /* default ifindex for this bcm_op */
+ int ifindex;
struct bcm_msg_head msg_head;
int cfsiz;
int ret; /* read bytes or error codes as return value */
- if (!bo->bound)
+ /* Lockless fast-path check for bound socket */
+ if (!READ_ONCE(bo->bound))
return -ENOTCONN;
/* check for valid message length from userspace */
if (size < MHSIZ)
return -EINVAL;
@@ -1415,43 +1421,65 @@ static int bcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
cfsiz = CFSIZ(msg_head.flags);
if ((size - MHSIZ) % cfsiz)
return -EINVAL;
+ lock_sock(sk);
+
+ /* Re-validate under the socket lock: a concurrent bcm_notify()
+ * may have unbound this socket (device removal) after the
+ * lockless fast-path check above. bo->ifindex is only ever
+ * mutated under lock_sock(), so reading it here - instead of
+ * before taking the lock - guarantees it can't be observed
+ * torn against bo->bound.
+ */
+ if (!bo->bound) {
+ ret = -ENOTCONN;
+ goto out_release;
+ }
+
+ /* default ifindex for this bcm_op */
+ ifindex = bo->ifindex;
+
/* check for alternative ifindex for this bcm_op */
if (!ifindex && msg->msg_name) {
/* no bound device as default => check msg_name */
DECLARE_SOCKADDR(struct sockaddr_can *, addr, msg->msg_name);
- if (msg->msg_namelen < BCM_MIN_NAMELEN)
- return -EINVAL;
+ if (msg->msg_namelen < BCM_MIN_NAMELEN) {
+ ret = -EINVAL;
+ goto out_release;
+ }
- if (addr->can_family != AF_CAN)
- return -EINVAL;
+ if (addr->can_family != AF_CAN) {
+ ret = -EINVAL;
+ goto out_release;
+ }
/* ifindex from sendto() */
ifindex = addr->can_ifindex;
if (ifindex) {
struct net_device *dev;
dev = dev_get_by_index(sock_net(sk), ifindex);
- if (!dev)
- return -ENODEV;
+ if (!dev) {
+ ret = -ENODEV;
+ goto out_release;
+ }
if (dev->type != ARPHRD_CAN) {
dev_put(dev);
- return -ENODEV;
+ ret = -ENODEV;
+ goto out_release;
}
dev_put(dev);
}
}
- lock_sock(sk);
-
switch (msg_head.opcode) {
case TX_SETUP:
ret = bcm_tx_setup(&msg_head, msg, ifindex, sk);
break;
@@ -1497,10 +1525,11 @@ static int bcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
default:
ret = -EINVAL;
break;
}
+out_release:
release_sock(sk);
return ret;
}
@@ -1533,11 +1562,16 @@ static void bcm_notify(struct bcm_sock *bo, unsigned long msg,
if (sock_net(sk)->can.bcmproc_dir && bo->bcm_proc_read) {
remove_proc_entry(bo->procname, sock_net(sk)->can.bcmproc_dir);
bo->bcm_proc_read = NULL;
}
#endif
- bo->bound = 0;
+ /* Paired with the lockless fast-path check in
+ * bcm_sendmsg(); bo->ifindex itself is only ever
+ * accessed under lock_sock() so it needs no
+ * annotation.
+ */
+ WRITE_ONCE(bo->bound, 0);
bo->ifindex = 0;
notify_enodev = 1;
}
release_sock(sk);
@@ -1674,11 +1708,11 @@ static int bcm_release(struct socket *sock)
list_for_each_entry_safe(op, next, &bo->rx_ops, list)
bcm_remove_op(op);
/* remove device reference */
if (bo->bound) {
- bo->bound = 0;
+ WRITE_ONCE(bo->bound, 0);
bo->ifindex = 0;
}
sock_orphan(sk);
sock->sk = NULL;
@@ -1744,11 +1778,14 @@ static int bcm_connect(struct socket *sock, struct sockaddr_unsized *uaddr, int
goto fail;
}
}
#endif /* CONFIG_PROC_FS */
- bo->bound = 1;
+ /* bo->ifindex above is fully assigned before this point; pairs
+ * with the lockless fast-path check in bcm_sendmsg()
+ */
+ WRITE_ONCE(bo->bound, 1);
fail:
release_sock(sk);
return ret;
--
2.53.0
^ permalink raw reply related [flat|nested] 29+ messages in thread
* [PATCH v7 03/10] can: bcm: add locking when updating filter and timer values
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
@ 2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
-1 siblings, 0 replies; 29+ messages in thread
From: Oliver Hartkopp @ 2026-07-08 15:21 UTC (permalink / raw)
To: linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde, syzbot+75e5e4ae00c3b4bb544e
KCSAN detected a simultaneous access to timer values that can be
overwritten in bcm_rx_setup() when updating timer and filter content
while bcm_rx_handler(), bcm_rx_timeout_handler() or bcm_rx_thr_handler()
run concurrently on incoming CAN traffic.
Protect the timer (ival1/ival2/kt_ival1/kt_ival2/kt_lastmsg) and filter
(nframes/flags/frames/last_frames) updates in bcm_rx_setup() with a new
per-op bcm_rx_update_lock, taken with the matching scope in the RX
handlers. memcpy_from_msg() is staged into a temporary buffer before the
lock is taken, since it can sleep and must not run under a spinlock.
hrtimer_cancel() is always called without bcm_rx_update_lock held, since
bcm_rx_timeout_handler()/bcm_rx_thr_handler() take the same lock and a
running callback would otherwise deadlock against the canceller.
Also close a related race: bcm_rx_setup() cleared the RTR flag in the
stored reply frame's can_id as a separate, unprotected step after the
frame content was already installed, so a concurrent bcm_rx_handler()
could transmit a stale reply with CAN_RTR_FLAG still set. Fold that
normalization into the initial frame preparation instead (on the staged
buffer for updates, directly on op->frames pre-registration for new
ops), so the installed frame is always atomically self-consistent.
bcm_rx_handler()'s RX_RTR_FRAME check now takes a lock-protected
snapshot of op->flags before deciding whether to call bcm_can_tx(),
but does not hold the lock across that call.
Also take a lock-protected snapshot of the currframe in bcm_can_tx()
to avoid partly overwrites by content updates in bcm_tx_setup().
Omit calling hrtimer_forward() with zero interval in bcm_rx_thr_handler().
kt_ival2 may have been concurrently cleared by bcm_rx_setup() before it
cancels this timer, so check kt_ival2 inside the bcm_rx_update_lock.
Fixes: c2aba69d0c36 ("can: bcm: add locking for bcm_op runtime updates")
Reported-by: syzbot+75e5e4ae00c3b4bb544e@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/linux-can/6975d5cf.a00a0220.33ccc7.0022.GAE@google.com/
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
net/can/bcm.c | 136 ++++++++++++++++++++++++++++++++++++++++++++--------------
1 file changed, 104 insertions(+), 32 deletions(-)
diff --git a/net/can/bcm.c b/net/can/bcm.c
index b612135b017d..af4bb4182bc2 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -127,10 +127,11 @@ struct bcm_op {
struct canfd_frame sframe;
struct canfd_frame last_sframe;
struct sock *sk;
struct net_device *rx_reg_dev;
spinlock_t bcm_tx_lock; /* protect currframe/count in runtime updates */
+ spinlock_t bcm_rx_update_lock; /* protect filter/timer data updates */
};
struct bcm_sock {
struct sock sk;
int bound;
@@ -291,26 +292,30 @@ static int bcm_proc_show(struct seq_file *m, void *v)
/*
* bcm_can_tx - send the (next) CAN frame to the appropriate CAN interface
* of the given bcm tx op
*/
-static void bcm_can_tx(struct bcm_op *op)
+static void bcm_can_tx(struct bcm_op *op, struct canfd_frame *cf)
{
struct sk_buff *skb;
struct can_skb_ext *csx;
struct net_device *dev;
- struct canfd_frame *cf;
+ struct canfd_frame cframe;
int err;
/* no target device? => exit */
if (!op->ifindex)
return;
- /* read currframe under lock protection */
- spin_lock_bh(&op->bcm_tx_lock);
- cf = op->frames + op->cfsiz * op->currframe;
- spin_unlock_bh(&op->bcm_tx_lock);
+ if (!cf) {
+ /* read currframe under lock protection */
+ spin_lock_bh(&op->bcm_tx_lock);
+ memcpy(&cframe, op->frames + op->cfsiz * op->currframe,
+ op->cfsiz);
+ cf = &cframe;
+ spin_unlock_bh(&op->bcm_tx_lock);
+ }
dev = dev_get_by_index(sock_net(op->sk), op->ifindex);
if (!dev) {
/* RFC: should this bcm_op remove itself here? */
return;
@@ -459,11 +464,11 @@ static enum hrtimer_restart bcm_tx_timeout_handler(struct hrtimer *hrtimer)
{
struct bcm_op *op = container_of(hrtimer, struct bcm_op, timer);
struct bcm_msg_head msg_head;
if (op->kt_ival1 && (op->count > 0)) {
- bcm_can_tx(op);
+ bcm_can_tx(op, NULL);
if (!op->count && (op->flags & TX_COUNTEVT)) {
/* create notification to user */
memset(&msg_head, 0, sizeof(msg_head));
msg_head.opcode = TX_EXPIRED;
@@ -476,11 +481,11 @@ static enum hrtimer_restart bcm_tx_timeout_handler(struct hrtimer *hrtimer)
bcm_send_to_user(op, &msg_head, NULL, 0);
}
} else if (op->kt_ival2) {
- bcm_can_tx(op);
+ bcm_can_tx(op, NULL);
}
return bcm_tx_set_expiry(op, &op->timer) ?
HRTIMER_RESTART : HRTIMER_NORESTART;
}
@@ -620,10 +625,12 @@ static void bcm_rx_starttimer(struct bcm_op *op)
static enum hrtimer_restart bcm_rx_timeout_handler(struct hrtimer *hrtimer)
{
struct bcm_op *op = container_of(hrtimer, struct bcm_op, timer);
struct bcm_msg_head msg_head;
+ spin_lock_bh(&op->bcm_rx_update_lock);
+
/* if user wants to be informed, when cyclic CAN-Messages come back */
if ((op->flags & RX_ANNOUNCE_RESUME) && op->last_frames) {
/* clear received CAN frames to indicate 'nothing received' */
memset(op->last_frames, 0, op->nframes * op->cfsiz);
}
@@ -636,10 +643,12 @@ static enum hrtimer_restart bcm_rx_timeout_handler(struct hrtimer *hrtimer)
msg_head.ival1 = op->ival1;
msg_head.ival2 = op->ival2;
msg_head.can_id = op->can_id;
msg_head.nframes = 0;
+ spin_unlock_bh(&op->bcm_rx_update_lock);
+
bcm_send_to_user(op, &msg_head, NULL, 0);
return HRTIMER_NORESTART;
}
@@ -684,30 +693,43 @@ static int bcm_rx_thr_flush(struct bcm_op *op)
* Check for throttled data and send it to the userspace
*/
static enum hrtimer_restart bcm_rx_thr_handler(struct hrtimer *hrtimer)
{
struct bcm_op *op = container_of(hrtimer, struct bcm_op, thrtimer);
+ enum hrtimer_restart ret;
+
+ spin_lock_bh(&op->bcm_rx_update_lock);
- if (bcm_rx_thr_flush(op)) {
+ /* kt_ival2 may have been concurrently cleared by bcm_rx_setup()
+ * before it cancels this timer - never forward with a zero
+ * interval in that case.
+ */
+ if (bcm_rx_thr_flush(op) && op->kt_ival2) {
hrtimer_forward_now(hrtimer, op->kt_ival2);
- return HRTIMER_RESTART;
+ ret = HRTIMER_RESTART;
} else {
/* rearm throttle handling */
op->kt_lastmsg = 0;
- return HRTIMER_NORESTART;
+ ret = HRTIMER_NORESTART;
}
+
+ spin_unlock_bh(&op->bcm_rx_update_lock);
+
+ return ret;
}
/*
* bcm_rx_handler - handle a CAN frame reception
*/
static void bcm_rx_handler(struct sk_buff *skb, void *data)
{
struct bcm_op *op = (struct bcm_op *)data;
const struct canfd_frame *rxframe = (struct canfd_frame *)skb->data;
+ struct canfd_frame rtrframe;
unsigned int i;
unsigned char traffic_flags;
+ bool rtr_frame;
if (op->can_id != rxframe->can_id)
return;
/* make sure to handle the correct frame type (CAN / CAN FD) */
@@ -727,13 +749,22 @@ static void bcm_rx_handler(struct sk_buff *skb, void *data)
/* save originator for recvfrom() */
op->rx_ifindex = skb->dev->ifindex;
/* update statistics */
op->frames_abs++;
- if (op->flags & RX_RTR_FRAME) {
+ /* snapshot the flag under lock: op->flags/op->frames may be updated
+ * concurrently by bcm_rx_setup().
+ */
+ spin_lock_bh(&op->bcm_rx_update_lock);
+ rtr_frame = op->flags & RX_RTR_FRAME;
+ if (rtr_frame)
+ memcpy(&rtrframe, op->frames, op->cfsiz);
+ spin_unlock_bh(&op->bcm_rx_update_lock);
+
+ if (rtr_frame) {
/* send reply for RTR-request (placed in op->frames[0]) */
- bcm_can_tx(op);
+ bcm_can_tx(op, &rtrframe);
return;
}
/* compute flags to distinguish between own/local/remote CAN traffic */
traffic_flags = 0;
@@ -741,10 +772,12 @@ static void bcm_rx_handler(struct sk_buff *skb, void *data)
traffic_flags |= RX_LOCAL;
if (skb->sk == op->sk)
traffic_flags |= RX_OWN;
}
+ spin_lock_bh(&op->bcm_rx_update_lock);
+
if (op->flags & RX_FILTER_ID) {
/* the easiest case */
bcm_rx_update_and_send(op, op->last_frames, rxframe,
traffic_flags);
goto rx_starttimer;
@@ -776,10 +809,12 @@ static void bcm_rx_handler(struct sk_buff *skb, void *data)
}
}
rx_starttimer:
bcm_rx_starttimer(op);
+
+ spin_unlock_bh(&op->bcm_rx_update_lock);
}
/*
* helpers for bcm_op handling: find & delete bcm [rx|tx] op elements
*/
@@ -1114,11 +1149,11 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
/* spec: send CAN frame when starting timer */
op->flags |= TX_ANNOUNCE;
}
if (op->flags & TX_ANNOUNCE)
- bcm_can_tx(op);
+ bcm_can_tx(op, NULL);
if (op->flags & STARTTIMER)
bcm_tx_start_timer(op);
return msg_head->nframes * op->cfsiz + MHSIZ;
@@ -1128,10 +1163,28 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
kfree(op->frames);
kfree(op);
return err;
}
+static void bcm_rx_setup_rtr_check(struct bcm_msg_head *msg_head,
+ struct bcm_op *op, void *new_frames)
+{
+ /* funny feature in RX(!)_SETUP only for RTR-mode:
+ * copy can_id into frame BUT without RTR-flag to
+ * prevent a full-load-loopback-test ... ;-]
+ * normalize this on the staged buffer, before it is
+ * ever installed into op->frames.
+ */
+ if (msg_head->flags & RX_RTR_FRAME) {
+ struct canfd_frame *frame0 = new_frames;
+
+ if ((msg_head->flags & TX_CP_CAN_ID) ||
+ frame0->can_id == op->can_id)
+ frame0->can_id = op->can_id & ~CAN_RTR_FLAG;
+ }
+}
+
/*
* bcm_rx_setup - create or update a bcm rx op (for bcm_sendmsg)
*/
static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
int ifindex, struct sock *sk)
@@ -1162,10 +1215,12 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
return -EINVAL;
/* check the given can_id */
op = bcm_find_op(&bo->rx_ops, msg_head, ifindex);
if (op) {
+ void *new_frames = NULL;
+
/* update existing BCM operation */
/*
* Do we need more space for the CAN frames than currently
* allocated? -> This is a _really_ unusual use-case and
@@ -1173,33 +1228,55 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
*/
if (msg_head->nframes > op->nframes)
return -E2BIG;
if (msg_head->nframes) {
- /* update CAN frames content */
- err = memcpy_from_msg(op->frames, msg,
+ /* get new CAN frames content before locking */
+ new_frames = kmalloc(msg_head->nframes * op->cfsiz,
+ GFP_KERNEL);
+ if (!new_frames)
+ return -ENOMEM;
+
+ err = memcpy_from_msg(new_frames, msg,
msg_head->nframes * op->cfsiz);
- if (err < 0)
+ if (err < 0) {
+ kfree(new_frames);
return err;
+ }
- /* clear last_frames to indicate 'nothing received' */
- memset(op->last_frames, 0, msg_head->nframes * op->cfsiz);
+ bcm_rx_setup_rtr_check(msg_head, op, new_frames);
}
+ spin_lock_bh(&op->bcm_rx_update_lock);
op->nframes = msg_head->nframes;
op->flags = msg_head->flags;
+ if (msg_head->nframes) {
+ /* update CAN frames content */
+ memcpy(op->frames, new_frames,
+ msg_head->nframes * op->cfsiz);
+
+ /* clear last_frames to indicate 'nothing received' */
+ memset(op->last_frames, 0,
+ msg_head->nframes * op->cfsiz);
+ }
+ spin_unlock_bh(&op->bcm_rx_update_lock);
+
+ /* free temporary frames / kfree(NULL) is safe */
+ kfree(new_frames);
+
/* Only an update -> do not call can_rx_register() */
do_rx_register = 0;
} else {
/* insert new BCM operation for the given can_id */
op = kzalloc(OPSIZ, GFP_KERNEL);
if (!op)
return -ENOMEM;
spin_lock_init(&op->bcm_tx_lock);
+ spin_lock_init(&op->bcm_rx_update_lock);
op->can_id = msg_head->can_id;
op->nframes = msg_head->nframes;
op->cfsiz = CFSIZ(msg_head->flags);
op->flags = msg_head->flags;
@@ -1237,10 +1314,12 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
if (op->last_frames != &op->last_sframe)
kfree(op->last_frames);
kfree(op);
return err;
}
+
+ bcm_rx_setup_rtr_check(msg_head, op, op->frames);
}
/* bcm_can_tx / bcm_tx_timeout_handler needs this */
op->sk = sk;
sock_hold(sk);
@@ -1264,45 +1343,38 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
} /* if ((op = bcm_find_op(&bo->rx_ops, msg_head->can_id, ifindex))) */
/* check flags */
if (op->flags & RX_RTR_FRAME) {
- struct canfd_frame *frame0 = op->frames;
-
/* no timers in RTR-mode */
hrtimer_cancel(&op->thrtimer);
hrtimer_cancel(&op->timer);
-
- /*
- * funny feature in RX(!)_SETUP only for RTR-mode:
- * copy can_id into frame BUT without RTR-flag to
- * prevent a full-load-loopback-test ... ;-]
- */
- if ((op->flags & TX_CP_CAN_ID) ||
- (frame0->can_id == op->can_id))
- frame0->can_id = op->can_id & ~CAN_RTR_FLAG;
-
} else {
if (op->flags & SETTIMER) {
/* set timer value */
+ spin_lock_bh(&op->bcm_rx_update_lock);
op->ival1 = msg_head->ival1;
op->ival2 = msg_head->ival2;
op->kt_ival1 = bcm_timeval_to_ktime(msg_head->ival1);
op->kt_ival2 = bcm_timeval_to_ktime(msg_head->ival2);
+ op->kt_lastmsg = 0;
+ spin_unlock_bh(&op->bcm_rx_update_lock);
/* disable an active timer due to zero value? */
if (!op->kt_ival1)
hrtimer_cancel(&op->timer);
/*
* In any case cancel the throttle timer, flush
* potentially blocked msgs and reset throttle handling
*/
- op->kt_lastmsg = 0;
hrtimer_cancel(&op->thrtimer);
+
+ spin_lock_bh(&op->bcm_rx_update_lock);
bcm_rx_thr_flush(op);
+ spin_unlock_bh(&op->bcm_rx_update_lock);
}
if ((op->flags & STARTTIMER) && op->kt_ival1)
hrtimer_start(&op->timer, op->kt_ival1,
HRTIMER_MODE_REL_SOFT);
--
2.53.0
^ permalink raw reply related [flat|nested] 29+ messages in thread
* [PATCH v7 03/10] can: bcm: add locking when updating filter and timer values
@ 2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
0 siblings, 0 replies; 29+ messages in thread
From: Oliver Hartkopp via B4 Relay @ 2026-07-08 15:21 UTC (permalink / raw)
To: linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde, syzbot+75e5e4ae00c3b4bb544e
From: Oliver Hartkopp <socketcan@hartkopp.net>
KCSAN detected a simultaneous access to timer values that can be
overwritten in bcm_rx_setup() when updating timer and filter content
while bcm_rx_handler(), bcm_rx_timeout_handler() or bcm_rx_thr_handler()
run concurrently on incoming CAN traffic.
Protect the timer (ival1/ival2/kt_ival1/kt_ival2/kt_lastmsg) and filter
(nframes/flags/frames/last_frames) updates in bcm_rx_setup() with a new
per-op bcm_rx_update_lock, taken with the matching scope in the RX
handlers. memcpy_from_msg() is staged into a temporary buffer before the
lock is taken, since it can sleep and must not run under a spinlock.
hrtimer_cancel() is always called without bcm_rx_update_lock held, since
bcm_rx_timeout_handler()/bcm_rx_thr_handler() take the same lock and a
running callback would otherwise deadlock against the canceller.
Also close a related race: bcm_rx_setup() cleared the RTR flag in the
stored reply frame's can_id as a separate, unprotected step after the
frame content was already installed, so a concurrent bcm_rx_handler()
could transmit a stale reply with CAN_RTR_FLAG still set. Fold that
normalization into the initial frame preparation instead (on the staged
buffer for updates, directly on op->frames pre-registration for new
ops), so the installed frame is always atomically self-consistent.
bcm_rx_handler()'s RX_RTR_FRAME check now takes a lock-protected
snapshot of op->flags before deciding whether to call bcm_can_tx(),
but does not hold the lock across that call.
Also take a lock-protected snapshot of the currframe in bcm_can_tx()
to avoid partly overwrites by content updates in bcm_tx_setup().
Omit calling hrtimer_forward() with zero interval in bcm_rx_thr_handler().
kt_ival2 may have been concurrently cleared by bcm_rx_setup() before it
cancels this timer, so check kt_ival2 inside the bcm_rx_update_lock.
Fixes: c2aba69d0c36 ("can: bcm: add locking for bcm_op runtime updates")
Reported-by: syzbot+75e5e4ae00c3b4bb544e@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/linux-can/6975d5cf.a00a0220.33ccc7.0022.GAE@google.com/
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
net/can/bcm.c | 136 ++++++++++++++++++++++++++++++++++++++++++++--------------
1 file changed, 104 insertions(+), 32 deletions(-)
diff --git a/net/can/bcm.c b/net/can/bcm.c
index b612135b017d..af4bb4182bc2 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -127,10 +127,11 @@ struct bcm_op {
struct canfd_frame sframe;
struct canfd_frame last_sframe;
struct sock *sk;
struct net_device *rx_reg_dev;
spinlock_t bcm_tx_lock; /* protect currframe/count in runtime updates */
+ spinlock_t bcm_rx_update_lock; /* protect filter/timer data updates */
};
struct bcm_sock {
struct sock sk;
int bound;
@@ -291,26 +292,30 @@ static int bcm_proc_show(struct seq_file *m, void *v)
/*
* bcm_can_tx - send the (next) CAN frame to the appropriate CAN interface
* of the given bcm tx op
*/
-static void bcm_can_tx(struct bcm_op *op)
+static void bcm_can_tx(struct bcm_op *op, struct canfd_frame *cf)
{
struct sk_buff *skb;
struct can_skb_ext *csx;
struct net_device *dev;
- struct canfd_frame *cf;
+ struct canfd_frame cframe;
int err;
/* no target device? => exit */
if (!op->ifindex)
return;
- /* read currframe under lock protection */
- spin_lock_bh(&op->bcm_tx_lock);
- cf = op->frames + op->cfsiz * op->currframe;
- spin_unlock_bh(&op->bcm_tx_lock);
+ if (!cf) {
+ /* read currframe under lock protection */
+ spin_lock_bh(&op->bcm_tx_lock);
+ memcpy(&cframe, op->frames + op->cfsiz * op->currframe,
+ op->cfsiz);
+ cf = &cframe;
+ spin_unlock_bh(&op->bcm_tx_lock);
+ }
dev = dev_get_by_index(sock_net(op->sk), op->ifindex);
if (!dev) {
/* RFC: should this bcm_op remove itself here? */
return;
@@ -459,11 +464,11 @@ static enum hrtimer_restart bcm_tx_timeout_handler(struct hrtimer *hrtimer)
{
struct bcm_op *op = container_of(hrtimer, struct bcm_op, timer);
struct bcm_msg_head msg_head;
if (op->kt_ival1 && (op->count > 0)) {
- bcm_can_tx(op);
+ bcm_can_tx(op, NULL);
if (!op->count && (op->flags & TX_COUNTEVT)) {
/* create notification to user */
memset(&msg_head, 0, sizeof(msg_head));
msg_head.opcode = TX_EXPIRED;
@@ -476,11 +481,11 @@ static enum hrtimer_restart bcm_tx_timeout_handler(struct hrtimer *hrtimer)
bcm_send_to_user(op, &msg_head, NULL, 0);
}
} else if (op->kt_ival2) {
- bcm_can_tx(op);
+ bcm_can_tx(op, NULL);
}
return bcm_tx_set_expiry(op, &op->timer) ?
HRTIMER_RESTART : HRTIMER_NORESTART;
}
@@ -620,10 +625,12 @@ static void bcm_rx_starttimer(struct bcm_op *op)
static enum hrtimer_restart bcm_rx_timeout_handler(struct hrtimer *hrtimer)
{
struct bcm_op *op = container_of(hrtimer, struct bcm_op, timer);
struct bcm_msg_head msg_head;
+ spin_lock_bh(&op->bcm_rx_update_lock);
+
/* if user wants to be informed, when cyclic CAN-Messages come back */
if ((op->flags & RX_ANNOUNCE_RESUME) && op->last_frames) {
/* clear received CAN frames to indicate 'nothing received' */
memset(op->last_frames, 0, op->nframes * op->cfsiz);
}
@@ -636,10 +643,12 @@ static enum hrtimer_restart bcm_rx_timeout_handler(struct hrtimer *hrtimer)
msg_head.ival1 = op->ival1;
msg_head.ival2 = op->ival2;
msg_head.can_id = op->can_id;
msg_head.nframes = 0;
+ spin_unlock_bh(&op->bcm_rx_update_lock);
+
bcm_send_to_user(op, &msg_head, NULL, 0);
return HRTIMER_NORESTART;
}
@@ -684,30 +693,43 @@ static int bcm_rx_thr_flush(struct bcm_op *op)
* Check for throttled data and send it to the userspace
*/
static enum hrtimer_restart bcm_rx_thr_handler(struct hrtimer *hrtimer)
{
struct bcm_op *op = container_of(hrtimer, struct bcm_op, thrtimer);
+ enum hrtimer_restart ret;
+
+ spin_lock_bh(&op->bcm_rx_update_lock);
- if (bcm_rx_thr_flush(op)) {
+ /* kt_ival2 may have been concurrently cleared by bcm_rx_setup()
+ * before it cancels this timer - never forward with a zero
+ * interval in that case.
+ */
+ if (bcm_rx_thr_flush(op) && op->kt_ival2) {
hrtimer_forward_now(hrtimer, op->kt_ival2);
- return HRTIMER_RESTART;
+ ret = HRTIMER_RESTART;
} else {
/* rearm throttle handling */
op->kt_lastmsg = 0;
- return HRTIMER_NORESTART;
+ ret = HRTIMER_NORESTART;
}
+
+ spin_unlock_bh(&op->bcm_rx_update_lock);
+
+ return ret;
}
/*
* bcm_rx_handler - handle a CAN frame reception
*/
static void bcm_rx_handler(struct sk_buff *skb, void *data)
{
struct bcm_op *op = (struct bcm_op *)data;
const struct canfd_frame *rxframe = (struct canfd_frame *)skb->data;
+ struct canfd_frame rtrframe;
unsigned int i;
unsigned char traffic_flags;
+ bool rtr_frame;
if (op->can_id != rxframe->can_id)
return;
/* make sure to handle the correct frame type (CAN / CAN FD) */
@@ -727,13 +749,22 @@ static void bcm_rx_handler(struct sk_buff *skb, void *data)
/* save originator for recvfrom() */
op->rx_ifindex = skb->dev->ifindex;
/* update statistics */
op->frames_abs++;
- if (op->flags & RX_RTR_FRAME) {
+ /* snapshot the flag under lock: op->flags/op->frames may be updated
+ * concurrently by bcm_rx_setup().
+ */
+ spin_lock_bh(&op->bcm_rx_update_lock);
+ rtr_frame = op->flags & RX_RTR_FRAME;
+ if (rtr_frame)
+ memcpy(&rtrframe, op->frames, op->cfsiz);
+ spin_unlock_bh(&op->bcm_rx_update_lock);
+
+ if (rtr_frame) {
/* send reply for RTR-request (placed in op->frames[0]) */
- bcm_can_tx(op);
+ bcm_can_tx(op, &rtrframe);
return;
}
/* compute flags to distinguish between own/local/remote CAN traffic */
traffic_flags = 0;
@@ -741,10 +772,12 @@ static void bcm_rx_handler(struct sk_buff *skb, void *data)
traffic_flags |= RX_LOCAL;
if (skb->sk == op->sk)
traffic_flags |= RX_OWN;
}
+ spin_lock_bh(&op->bcm_rx_update_lock);
+
if (op->flags & RX_FILTER_ID) {
/* the easiest case */
bcm_rx_update_and_send(op, op->last_frames, rxframe,
traffic_flags);
goto rx_starttimer;
@@ -776,10 +809,12 @@ static void bcm_rx_handler(struct sk_buff *skb, void *data)
}
}
rx_starttimer:
bcm_rx_starttimer(op);
+
+ spin_unlock_bh(&op->bcm_rx_update_lock);
}
/*
* helpers for bcm_op handling: find & delete bcm [rx|tx] op elements
*/
@@ -1114,11 +1149,11 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
/* spec: send CAN frame when starting timer */
op->flags |= TX_ANNOUNCE;
}
if (op->flags & TX_ANNOUNCE)
- bcm_can_tx(op);
+ bcm_can_tx(op, NULL);
if (op->flags & STARTTIMER)
bcm_tx_start_timer(op);
return msg_head->nframes * op->cfsiz + MHSIZ;
@@ -1128,10 +1163,28 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
kfree(op->frames);
kfree(op);
return err;
}
+static void bcm_rx_setup_rtr_check(struct bcm_msg_head *msg_head,
+ struct bcm_op *op, void *new_frames)
+{
+ /* funny feature in RX(!)_SETUP only for RTR-mode:
+ * copy can_id into frame BUT without RTR-flag to
+ * prevent a full-load-loopback-test ... ;-]
+ * normalize this on the staged buffer, before it is
+ * ever installed into op->frames.
+ */
+ if (msg_head->flags & RX_RTR_FRAME) {
+ struct canfd_frame *frame0 = new_frames;
+
+ if ((msg_head->flags & TX_CP_CAN_ID) ||
+ frame0->can_id == op->can_id)
+ frame0->can_id = op->can_id & ~CAN_RTR_FLAG;
+ }
+}
+
/*
* bcm_rx_setup - create or update a bcm rx op (for bcm_sendmsg)
*/
static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
int ifindex, struct sock *sk)
@@ -1162,10 +1215,12 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
return -EINVAL;
/* check the given can_id */
op = bcm_find_op(&bo->rx_ops, msg_head, ifindex);
if (op) {
+ void *new_frames = NULL;
+
/* update existing BCM operation */
/*
* Do we need more space for the CAN frames than currently
* allocated? -> This is a _really_ unusual use-case and
@@ -1173,33 +1228,55 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
*/
if (msg_head->nframes > op->nframes)
return -E2BIG;
if (msg_head->nframes) {
- /* update CAN frames content */
- err = memcpy_from_msg(op->frames, msg,
+ /* get new CAN frames content before locking */
+ new_frames = kmalloc(msg_head->nframes * op->cfsiz,
+ GFP_KERNEL);
+ if (!new_frames)
+ return -ENOMEM;
+
+ err = memcpy_from_msg(new_frames, msg,
msg_head->nframes * op->cfsiz);
- if (err < 0)
+ if (err < 0) {
+ kfree(new_frames);
return err;
+ }
- /* clear last_frames to indicate 'nothing received' */
- memset(op->last_frames, 0, msg_head->nframes * op->cfsiz);
+ bcm_rx_setup_rtr_check(msg_head, op, new_frames);
}
+ spin_lock_bh(&op->bcm_rx_update_lock);
op->nframes = msg_head->nframes;
op->flags = msg_head->flags;
+ if (msg_head->nframes) {
+ /* update CAN frames content */
+ memcpy(op->frames, new_frames,
+ msg_head->nframes * op->cfsiz);
+
+ /* clear last_frames to indicate 'nothing received' */
+ memset(op->last_frames, 0,
+ msg_head->nframes * op->cfsiz);
+ }
+ spin_unlock_bh(&op->bcm_rx_update_lock);
+
+ /* free temporary frames / kfree(NULL) is safe */
+ kfree(new_frames);
+
/* Only an update -> do not call can_rx_register() */
do_rx_register = 0;
} else {
/* insert new BCM operation for the given can_id */
op = kzalloc(OPSIZ, GFP_KERNEL);
if (!op)
return -ENOMEM;
spin_lock_init(&op->bcm_tx_lock);
+ spin_lock_init(&op->bcm_rx_update_lock);
op->can_id = msg_head->can_id;
op->nframes = msg_head->nframes;
op->cfsiz = CFSIZ(msg_head->flags);
op->flags = msg_head->flags;
@@ -1237,10 +1314,12 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
if (op->last_frames != &op->last_sframe)
kfree(op->last_frames);
kfree(op);
return err;
}
+
+ bcm_rx_setup_rtr_check(msg_head, op, op->frames);
}
/* bcm_can_tx / bcm_tx_timeout_handler needs this */
op->sk = sk;
sock_hold(sk);
@@ -1264,45 +1343,38 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
} /* if ((op = bcm_find_op(&bo->rx_ops, msg_head->can_id, ifindex))) */
/* check flags */
if (op->flags & RX_RTR_FRAME) {
- struct canfd_frame *frame0 = op->frames;
-
/* no timers in RTR-mode */
hrtimer_cancel(&op->thrtimer);
hrtimer_cancel(&op->timer);
-
- /*
- * funny feature in RX(!)_SETUP only for RTR-mode:
- * copy can_id into frame BUT without RTR-flag to
- * prevent a full-load-loopback-test ... ;-]
- */
- if ((op->flags & TX_CP_CAN_ID) ||
- (frame0->can_id == op->can_id))
- frame0->can_id = op->can_id & ~CAN_RTR_FLAG;
-
} else {
if (op->flags & SETTIMER) {
/* set timer value */
+ spin_lock_bh(&op->bcm_rx_update_lock);
op->ival1 = msg_head->ival1;
op->ival2 = msg_head->ival2;
op->kt_ival1 = bcm_timeval_to_ktime(msg_head->ival1);
op->kt_ival2 = bcm_timeval_to_ktime(msg_head->ival2);
+ op->kt_lastmsg = 0;
+ spin_unlock_bh(&op->bcm_rx_update_lock);
/* disable an active timer due to zero value? */
if (!op->kt_ival1)
hrtimer_cancel(&op->timer);
/*
* In any case cancel the throttle timer, flush
* potentially blocked msgs and reset throttle handling
*/
- op->kt_lastmsg = 0;
hrtimer_cancel(&op->thrtimer);
+
+ spin_lock_bh(&op->bcm_rx_update_lock);
bcm_rx_thr_flush(op);
+ spin_unlock_bh(&op->bcm_rx_update_lock);
}
if ((op->flags & STARTTIMER) && op->kt_ival1)
hrtimer_start(&op->timer, op->kt_ival1,
HRTIMER_MODE_REL_SOFT);
--
2.53.0
^ permalink raw reply related [flat|nested] 29+ messages in thread
* [PATCH v7 04/10] can: bcm: fix CAN frame rx/tx statistics
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
@ 2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
-1 siblings, 0 replies; 29+ messages in thread
From: Oliver Hartkopp @ 2026-07-08 15:21 UTC (permalink / raw)
To: linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde
KCSAN detected a data race within the bcm_rx_handler() when two CAN frames
have been simultaneously received and processed in a single rx op by two
different CPUs.
Use atomic operations with (signed) long data types to access the
statistics in the hot path to fix the KCSAN complaint.
Additionally simplify the update and check of statistics overflow by
using the atomic operations in a separate bcm_update_stats() function and
put this function under bcm_rx_update_lock to prevent races when resetting
the counters.
Fixes: ffd980f976e7 ("[CAN]: Add broadcast manager (bcm) protocol")
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
net/can/bcm.c | 47 ++++++++++++++++++++++++++++++-----------------
1 file changed, 30 insertions(+), 17 deletions(-)
diff --git a/net/can/bcm.c b/net/can/bcm.c
index af4bb4182bc2..340b7fc89744 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -110,11 +110,11 @@ struct bcm_op {
struct rcu_head rcu;
struct work_struct work;
int ifindex;
canid_t can_id;
u32 flags;
- unsigned long frames_abs, frames_filtered;
+ atomic_long_t frames_abs, frames_filtered;
struct bcm_timeval ival1, ival2;
struct hrtimer timer, thrtimer;
ktime_t rx_stamp, kt_ival1, kt_ival2, kt_lastmsg;
int rx_ifindex;
int cfsiz;
@@ -227,14 +227,17 @@ static int bcm_proc_show(struct seq_file *m, void *v)
rcu_read_lock();
list_for_each_entry_rcu(op, &bo->rx_ops, list) {
- unsigned long reduction;
+ long reduction, frames_filtered, frames_abs;
+
+ frames_filtered = atomic_long_read(&op->frames_filtered);
+ frames_abs = atomic_long_read(&op->frames_abs);
/* print only active entries & prevent division by zero */
- if (!op->frames_abs)
+ if (!frames_abs)
continue;
seq_printf(m, "rx_op: %03X %-5s ", op->can_id,
bcm_proc_getifname(net, ifname, op->ifindex));
@@ -252,13 +255,13 @@ static int bcm_proc_show(struct seq_file *m, void *v)
if (op->kt_ival2)
seq_printf(m, "thr=%lld ",
(long long)ktime_to_us(op->kt_ival2));
seq_printf(m, "# recv %ld (%ld) => reduction: ",
- op->frames_filtered, op->frames_abs);
+ frames_filtered, frames_abs);
- reduction = 100 - (op->frames_filtered * 100) / op->frames_abs;
+ reduction = 100 - (frames_filtered * 100) / frames_abs;
seq_printf(m, "%s%ld%%\n",
(reduction == 100) ? "near " : "", reduction);
}
@@ -278,20 +281,30 @@ static int bcm_proc_show(struct seq_file *m, void *v)
if (op->kt_ival2)
seq_printf(m, "t2=%lld ",
(long long)ktime_to_us(op->kt_ival2));
- seq_printf(m, "# sent %ld\n", op->frames_abs);
+ seq_printf(m, "# sent %ld\n",
+ atomic_long_read(&op->frames_abs));
}
seq_putc(m, '\n');
rcu_read_unlock();
return 0;
}
#endif /* CONFIG_PROC_FS */
+static void bcm_update_stats(struct bcm_op *op)
+{
+ /* prevent statistics overflow */
+ if (atomic_long_inc_return(&op->frames_abs) > LONG_MAX / 100) {
+ atomic_long_set(&op->frames_filtered, 0);
+ atomic_long_set(&op->frames_abs, 0);
+ }
+}
+
/*
* bcm_can_tx - send the (next) CAN frame to the appropriate CAN interface
* of the given bcm tx op
*/
static void bcm_can_tx(struct bcm_op *op, struct canfd_frame *cf)
@@ -342,11 +355,11 @@ static void bcm_can_tx(struct bcm_op *op, struct canfd_frame *cf)
/* update currframe and count under lock protection */
spin_lock_bh(&op->bcm_tx_lock);
if (!err)
- op->frames_abs++;
+ bcm_update_stats(op);
op->currframe++;
/* reached last frame? */
if (op->currframe >= op->nframes)
@@ -495,16 +508,13 @@ static enum hrtimer_restart bcm_tx_timeout_handler(struct hrtimer *hrtimer)
*/
static void bcm_rx_changed(struct bcm_op *op, struct canfd_frame *data)
{
struct bcm_msg_head head;
- /* update statistics */
- op->frames_filtered++;
-
- /* prevent statistics overflow */
- if (op->frames_filtered > ULONG_MAX/100)
- op->frames_filtered = op->frames_abs = 0;
+ /* update statistics (frames_filtered <= frames_abs) */
+ if (atomic_long_read(&op->frames_abs))
+ atomic_long_inc(&op->frames_filtered);
/* this element is not throttled anymore */
data->flags &= ~RX_THR;
memset(&head, 0, sizeof(head));
@@ -746,20 +756,23 @@ static void bcm_rx_handler(struct sk_buff *skb, void *data)
/* save rx timestamp */
op->rx_stamp = skb->tstamp;
/* save originator for recvfrom() */
op->rx_ifindex = skb->dev->ifindex;
- /* update statistics */
- op->frames_abs++;
- /* snapshot the flag under lock: op->flags/op->frames may be updated
- * concurrently by bcm_rx_setup().
+ /* snapshot RTR content under lock: op->flags/op->frames may be
+ * updated concurrently by bcm_rx_setup().
*/
spin_lock_bh(&op->bcm_rx_update_lock);
+
+ /* update statistics with lock analogue to bcm_rx_changed() callers */
+ bcm_update_stats(op);
+
rtr_frame = op->flags & RX_RTR_FRAME;
if (rtr_frame)
memcpy(&rtrframe, op->frames, op->cfsiz);
+
spin_unlock_bh(&op->bcm_rx_update_lock);
if (rtr_frame) {
/* send reply for RTR-request (placed in op->frames[0]) */
bcm_can_tx(op, &rtrframe);
--
2.53.0
^ permalink raw reply related [flat|nested] 29+ messages in thread
* [PATCH v7 04/10] can: bcm: fix CAN frame rx/tx statistics
@ 2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
0 siblings, 0 replies; 29+ messages in thread
From: Oliver Hartkopp via B4 Relay @ 2026-07-08 15:21 UTC (permalink / raw)
To: linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde
From: Oliver Hartkopp <socketcan@hartkopp.net>
KCSAN detected a data race within the bcm_rx_handler() when two CAN frames
have been simultaneously received and processed in a single rx op by two
different CPUs.
Use atomic operations with (signed) long data types to access the
statistics in the hot path to fix the KCSAN complaint.
Additionally simplify the update and check of statistics overflow by
using the atomic operations in a separate bcm_update_stats() function and
put this function under bcm_rx_update_lock to prevent races when resetting
the counters.
Fixes: ffd980f976e7 ("[CAN]: Add broadcast manager (bcm) protocol")
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
net/can/bcm.c | 47 ++++++++++++++++++++++++++++++-----------------
1 file changed, 30 insertions(+), 17 deletions(-)
diff --git a/net/can/bcm.c b/net/can/bcm.c
index af4bb4182bc2..340b7fc89744 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -110,11 +110,11 @@ struct bcm_op {
struct rcu_head rcu;
struct work_struct work;
int ifindex;
canid_t can_id;
u32 flags;
- unsigned long frames_abs, frames_filtered;
+ atomic_long_t frames_abs, frames_filtered;
struct bcm_timeval ival1, ival2;
struct hrtimer timer, thrtimer;
ktime_t rx_stamp, kt_ival1, kt_ival2, kt_lastmsg;
int rx_ifindex;
int cfsiz;
@@ -227,14 +227,17 @@ static int bcm_proc_show(struct seq_file *m, void *v)
rcu_read_lock();
list_for_each_entry_rcu(op, &bo->rx_ops, list) {
- unsigned long reduction;
+ long reduction, frames_filtered, frames_abs;
+
+ frames_filtered = atomic_long_read(&op->frames_filtered);
+ frames_abs = atomic_long_read(&op->frames_abs);
/* print only active entries & prevent division by zero */
- if (!op->frames_abs)
+ if (!frames_abs)
continue;
seq_printf(m, "rx_op: %03X %-5s ", op->can_id,
bcm_proc_getifname(net, ifname, op->ifindex));
@@ -252,13 +255,13 @@ static int bcm_proc_show(struct seq_file *m, void *v)
if (op->kt_ival2)
seq_printf(m, "thr=%lld ",
(long long)ktime_to_us(op->kt_ival2));
seq_printf(m, "# recv %ld (%ld) => reduction: ",
- op->frames_filtered, op->frames_abs);
+ frames_filtered, frames_abs);
- reduction = 100 - (op->frames_filtered * 100) / op->frames_abs;
+ reduction = 100 - (frames_filtered * 100) / frames_abs;
seq_printf(m, "%s%ld%%\n",
(reduction == 100) ? "near " : "", reduction);
}
@@ -278,20 +281,30 @@ static int bcm_proc_show(struct seq_file *m, void *v)
if (op->kt_ival2)
seq_printf(m, "t2=%lld ",
(long long)ktime_to_us(op->kt_ival2));
- seq_printf(m, "# sent %ld\n", op->frames_abs);
+ seq_printf(m, "# sent %ld\n",
+ atomic_long_read(&op->frames_abs));
}
seq_putc(m, '\n');
rcu_read_unlock();
return 0;
}
#endif /* CONFIG_PROC_FS */
+static void bcm_update_stats(struct bcm_op *op)
+{
+ /* prevent statistics overflow */
+ if (atomic_long_inc_return(&op->frames_abs) > LONG_MAX / 100) {
+ atomic_long_set(&op->frames_filtered, 0);
+ atomic_long_set(&op->frames_abs, 0);
+ }
+}
+
/*
* bcm_can_tx - send the (next) CAN frame to the appropriate CAN interface
* of the given bcm tx op
*/
static void bcm_can_tx(struct bcm_op *op, struct canfd_frame *cf)
@@ -342,11 +355,11 @@ static void bcm_can_tx(struct bcm_op *op, struct canfd_frame *cf)
/* update currframe and count under lock protection */
spin_lock_bh(&op->bcm_tx_lock);
if (!err)
- op->frames_abs++;
+ bcm_update_stats(op);
op->currframe++;
/* reached last frame? */
if (op->currframe >= op->nframes)
@@ -495,16 +508,13 @@ static enum hrtimer_restart bcm_tx_timeout_handler(struct hrtimer *hrtimer)
*/
static void bcm_rx_changed(struct bcm_op *op, struct canfd_frame *data)
{
struct bcm_msg_head head;
- /* update statistics */
- op->frames_filtered++;
-
- /* prevent statistics overflow */
- if (op->frames_filtered > ULONG_MAX/100)
- op->frames_filtered = op->frames_abs = 0;
+ /* update statistics (frames_filtered <= frames_abs) */
+ if (atomic_long_read(&op->frames_abs))
+ atomic_long_inc(&op->frames_filtered);
/* this element is not throttled anymore */
data->flags &= ~RX_THR;
memset(&head, 0, sizeof(head));
@@ -746,20 +756,23 @@ static void bcm_rx_handler(struct sk_buff *skb, void *data)
/* save rx timestamp */
op->rx_stamp = skb->tstamp;
/* save originator for recvfrom() */
op->rx_ifindex = skb->dev->ifindex;
- /* update statistics */
- op->frames_abs++;
- /* snapshot the flag under lock: op->flags/op->frames may be updated
- * concurrently by bcm_rx_setup().
+ /* snapshot RTR content under lock: op->flags/op->frames may be
+ * updated concurrently by bcm_rx_setup().
*/
spin_lock_bh(&op->bcm_rx_update_lock);
+
+ /* update statistics with lock analogue to bcm_rx_changed() callers */
+ bcm_update_stats(op);
+
rtr_frame = op->flags & RX_RTR_FRAME;
if (rtr_frame)
memcpy(&rtrframe, op->frames, op->cfsiz);
+
spin_unlock_bh(&op->bcm_rx_update_lock);
if (rtr_frame) {
/* send reply for RTR-request (placed in op->frames[0]) */
bcm_can_tx(op, &rtrframe);
--
2.53.0
^ permalink raw reply related [flat|nested] 29+ messages in thread
* [PATCH v7 05/10] can: bcm: add missing rcu list annotations and operations
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
@ 2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
-1 siblings, 0 replies; 29+ messages in thread
From: Oliver Hartkopp @ 2026-07-08 15:21 UTC (permalink / raw)
To: linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde, sashiko-reviews
sashiko-bot remarked the missing use of list_add_rcu() in
bcm_[rx|tx]_setup() to have a proper initialized bcm_op structure
when bcm_proc_show() traverses the bcm_op's under rcu_read_lock().
To cover all initial settings of the bcm_op's the list_add_rcu() calls
are moved to the end of the setup code.
While at it, also fix the mirroring removal side: bcm_release() called
bcm_remove_op() - which frees the op via call_rcu() - on ops that were
still linked in bo->tx_ops/bo->rx_ops, without list_del_rcu() first.
Unlink each op with list_del_rcu() before handing it to bcm_remove_op(),
matching the existing pattern in bcm_delete_tx_op()/bcm_delete_rx_op().
Reported-by: sashiko-reviews@lists.linux.dev
Closes: https://lore.kernel.org/linux-can/20260610094654.A1FFE1F00893@smtp.kernel.org/
Fixes: dac5e6249159 ("can: bcm: add missing rcu read protection for procfs content")
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
net/can/bcm.c | 25 ++++++++++++++++---------
1 file changed, 16 insertions(+), 9 deletions(-)
diff --git a/net/can/bcm.c b/net/can/bcm.c
index 340b7fc89744..fca7c714cc52 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -263,11 +263,11 @@ static int bcm_proc_show(struct seq_file *m, void *v)
seq_printf(m, "%s%ld%%\n",
(reduction == 100) ? "near " : "", reduction);
}
- list_for_each_entry(op, &bo->tx_ops, list) {
+ list_for_each_entry_rcu(op, &bo->tx_ops, list) {
seq_printf(m, "tx_op: %03X %s ", op->can_id,
bcm_proc_getifname(net, ifname, op->ifindex));
if (op->flags & CAN_FD_FRAME)
@@ -997,10 +997,11 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
int ifindex, struct sock *sk)
{
struct bcm_sock *bo = bcm_sk(sk);
struct bcm_op *op;
struct canfd_frame *cf;
+ bool add_op_to_list = false;
unsigned int i;
int err;
/* we need a real device to send frames */
if (!ifindex)
@@ -1138,12 +1139,11 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
/* currently unused in tx_ops */
hrtimer_setup(&op->thrtimer, hrtimer_dummy_timeout, CLOCK_MONOTONIC,
HRTIMER_MODE_REL_SOFT);
- /* add this bcm_op to the list of the tx_ops */
- list_add(&op->list, &bo->tx_ops);
+ add_op_to_list = true;
} /* if ((op = bcm_find_op(&bo->tx_ops, msg_head->can_id, ifindex))) */
if (op->flags & SETTIMER) {
/* set timer values */
@@ -1161,10 +1161,14 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
hrtimer_cancel(&op->timer);
/* spec: send CAN frame when starting timer */
op->flags |= TX_ANNOUNCE;
}
+ /* add this bcm_op to the list of the tx_ops? */
+ if (add_op_to_list)
+ list_add_rcu(&op->list, &bo->tx_ops);
+
if (op->flags & TX_ANNOUNCE)
bcm_can_tx(op, NULL);
if (op->flags & STARTTIMER)
bcm_tx_start_timer(op);
@@ -1345,13 +1349,10 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
hrtimer_setup(&op->timer, bcm_rx_timeout_handler, CLOCK_MONOTONIC,
HRTIMER_MODE_REL_SOFT);
hrtimer_setup(&op->thrtimer, bcm_rx_thr_handler, CLOCK_MONOTONIC,
HRTIMER_MODE_REL_SOFT);
- /* add this bcm_op to the list of the rx_ops */
- list_add(&op->list, &bo->rx_ops);
-
/* call can_rx_register() */
do_rx_register = 1;
} /* if ((op = bcm_find_op(&bo->rx_ops, msg_head->can_id, ifindex))) */
@@ -1419,14 +1420,16 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
err = can_rx_register(sock_net(sk), NULL, op->can_id,
REGMASK(op->can_id),
bcm_rx_handler, op, "bcm", sk);
if (err) {
/* this bcm rx op is broken -> remove it */
- list_del_rcu(&op->list);
bcm_remove_op(op);
return err;
}
+
+ /* add this bcm_op to the list of the rx_ops */
+ list_add_rcu(&op->list, &bo->rx_ops);
}
return msg_head->nframes * op->cfsiz + MHSIZ;
}
@@ -1756,12 +1759,14 @@ static int bcm_release(struct socket *sock)
/* remove procfs entry */
if (net->can.bcmproc_dir && bo->bcm_proc_read)
remove_proc_entry(bo->procname, net->can.bcmproc_dir);
#endif /* CONFIG_PROC_FS */
- list_for_each_entry_safe(op, next, &bo->tx_ops, list)
+ list_for_each_entry_safe(op, next, &bo->tx_ops, list) {
+ list_del_rcu(&op->list);
bcm_remove_op(op);
+ }
list_for_each_entry_safe(op, next, &bo->rx_ops, list) {
/*
* Don't care if we're bound or not (due to netdev problems)
* can_rx_unregister() is always a save thing to do here.
@@ -1788,12 +1793,14 @@ static int bcm_release(struct socket *sock)
}
synchronize_rcu();
- list_for_each_entry_safe(op, next, &bo->rx_ops, list)
+ list_for_each_entry_safe(op, next, &bo->rx_ops, list) {
+ list_del_rcu(&op->list);
bcm_remove_op(op);
+ }
/* remove device reference */
if (bo->bound) {
WRITE_ONCE(bo->bound, 0);
bo->ifindex = 0;
--
2.53.0
^ permalink raw reply related [flat|nested] 29+ messages in thread
* [PATCH v7 05/10] can: bcm: add missing rcu list annotations and operations
@ 2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
0 siblings, 0 replies; 29+ messages in thread
From: Oliver Hartkopp via B4 Relay @ 2026-07-08 15:21 UTC (permalink / raw)
To: linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde, sashiko-reviews
From: Oliver Hartkopp <socketcan@hartkopp.net>
sashiko-bot remarked the missing use of list_add_rcu() in
bcm_[rx|tx]_setup() to have a proper initialized bcm_op structure
when bcm_proc_show() traverses the bcm_op's under rcu_read_lock().
To cover all initial settings of the bcm_op's the list_add_rcu() calls
are moved to the end of the setup code.
While at it, also fix the mirroring removal side: bcm_release() called
bcm_remove_op() - which frees the op via call_rcu() - on ops that were
still linked in bo->tx_ops/bo->rx_ops, without list_del_rcu() first.
Unlink each op with list_del_rcu() before handing it to bcm_remove_op(),
matching the existing pattern in bcm_delete_tx_op()/bcm_delete_rx_op().
Reported-by: sashiko-reviews@lists.linux.dev
Closes: https://lore.kernel.org/linux-can/20260610094654.A1FFE1F00893@smtp.kernel.org/
Fixes: dac5e6249159 ("can: bcm: add missing rcu read protection for procfs content")
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
net/can/bcm.c | 25 ++++++++++++++++---------
1 file changed, 16 insertions(+), 9 deletions(-)
diff --git a/net/can/bcm.c b/net/can/bcm.c
index 340b7fc89744..fca7c714cc52 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -263,11 +263,11 @@ static int bcm_proc_show(struct seq_file *m, void *v)
seq_printf(m, "%s%ld%%\n",
(reduction == 100) ? "near " : "", reduction);
}
- list_for_each_entry(op, &bo->tx_ops, list) {
+ list_for_each_entry_rcu(op, &bo->tx_ops, list) {
seq_printf(m, "tx_op: %03X %s ", op->can_id,
bcm_proc_getifname(net, ifname, op->ifindex));
if (op->flags & CAN_FD_FRAME)
@@ -997,10 +997,11 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
int ifindex, struct sock *sk)
{
struct bcm_sock *bo = bcm_sk(sk);
struct bcm_op *op;
struct canfd_frame *cf;
+ bool add_op_to_list = false;
unsigned int i;
int err;
/* we need a real device to send frames */
if (!ifindex)
@@ -1138,12 +1139,11 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
/* currently unused in tx_ops */
hrtimer_setup(&op->thrtimer, hrtimer_dummy_timeout, CLOCK_MONOTONIC,
HRTIMER_MODE_REL_SOFT);
- /* add this bcm_op to the list of the tx_ops */
- list_add(&op->list, &bo->tx_ops);
+ add_op_to_list = true;
} /* if ((op = bcm_find_op(&bo->tx_ops, msg_head->can_id, ifindex))) */
if (op->flags & SETTIMER) {
/* set timer values */
@@ -1161,10 +1161,14 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
hrtimer_cancel(&op->timer);
/* spec: send CAN frame when starting timer */
op->flags |= TX_ANNOUNCE;
}
+ /* add this bcm_op to the list of the tx_ops? */
+ if (add_op_to_list)
+ list_add_rcu(&op->list, &bo->tx_ops);
+
if (op->flags & TX_ANNOUNCE)
bcm_can_tx(op, NULL);
if (op->flags & STARTTIMER)
bcm_tx_start_timer(op);
@@ -1345,13 +1349,10 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
hrtimer_setup(&op->timer, bcm_rx_timeout_handler, CLOCK_MONOTONIC,
HRTIMER_MODE_REL_SOFT);
hrtimer_setup(&op->thrtimer, bcm_rx_thr_handler, CLOCK_MONOTONIC,
HRTIMER_MODE_REL_SOFT);
- /* add this bcm_op to the list of the rx_ops */
- list_add(&op->list, &bo->rx_ops);
-
/* call can_rx_register() */
do_rx_register = 1;
} /* if ((op = bcm_find_op(&bo->rx_ops, msg_head->can_id, ifindex))) */
@@ -1419,14 +1420,16 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
err = can_rx_register(sock_net(sk), NULL, op->can_id,
REGMASK(op->can_id),
bcm_rx_handler, op, "bcm", sk);
if (err) {
/* this bcm rx op is broken -> remove it */
- list_del_rcu(&op->list);
bcm_remove_op(op);
return err;
}
+
+ /* add this bcm_op to the list of the rx_ops */
+ list_add_rcu(&op->list, &bo->rx_ops);
}
return msg_head->nframes * op->cfsiz + MHSIZ;
}
@@ -1756,12 +1759,14 @@ static int bcm_release(struct socket *sock)
/* remove procfs entry */
if (net->can.bcmproc_dir && bo->bcm_proc_read)
remove_proc_entry(bo->procname, net->can.bcmproc_dir);
#endif /* CONFIG_PROC_FS */
- list_for_each_entry_safe(op, next, &bo->tx_ops, list)
+ list_for_each_entry_safe(op, next, &bo->tx_ops, list) {
+ list_del_rcu(&op->list);
bcm_remove_op(op);
+ }
list_for_each_entry_safe(op, next, &bo->rx_ops, list) {
/*
* Don't care if we're bound or not (due to netdev problems)
* can_rx_unregister() is always a save thing to do here.
@@ -1788,12 +1793,14 @@ static int bcm_release(struct socket *sock)
}
synchronize_rcu();
- list_for_each_entry_safe(op, next, &bo->rx_ops, list)
+ list_for_each_entry_safe(op, next, &bo->rx_ops, list) {
+ list_del_rcu(&op->list);
bcm_remove_op(op);
+ }
/* remove device reference */
if (bo->bound) {
WRITE_ONCE(bo->bound, 0);
bo->ifindex = 0;
--
2.53.0
^ permalink raw reply related [flat|nested] 29+ messages in thread
* [PATCH v7 06/10] can: bcm: extend bcm_tx_lock usage for data and timer updates
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
@ 2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
-1 siblings, 0 replies; 29+ messages in thread
From: Oliver Hartkopp @ 2026-07-08 15:21 UTC (permalink / raw)
To: linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde
Stage new CAN frame content for an existing tx op into a kmalloc()'d
buffer and validate it there, mirroring the approach already used in
bcm_rx_setup(). Only copy the validated data into op->frames while
holding op->bcm_tx_lock, so bcm_can_tx() and bcm_tx_timeout_handler()
can no longer observe a partially updated or unvalidated frame.
Add a missing error path for memcpy_from_msg() when copying CAN frame
data from userspace.
Also move the kt_ival1/kt_ival2/ival1/ival2 updates in bcm_tx_setup()
under op->bcm_tx_lock, and read kt_ival1/kt_ival2/count under the same
lock in bcm_tx_set_expiry() and bcm_tx_timeout_handler(), closing the
torn 64-bit ktime_t read on 32-bit platforms.
Fixes: c2aba69d0c36 ("can: bcm: add locking for bcm_op runtime updates")
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
net/can/bcm.c | 81 +++++++++++++++++++++++++++++++++++++++++------------------
1 file changed, 57 insertions(+), 24 deletions(-)
diff --git a/net/can/bcm.c b/net/can/bcm.c
index fca7c714cc52..fefa77045253 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -126,11 +126,11 @@ struct bcm_op {
void *last_frames;
struct canfd_frame sframe;
struct canfd_frame last_sframe;
struct sock *sk;
struct net_device *rx_reg_dev;
- spinlock_t bcm_tx_lock; /* protect currframe/count in runtime updates */
+ spinlock_t bcm_tx_lock; /* protect tx data and timer updates */
spinlock_t bcm_rx_update_lock; /* protect filter/timer data updates */
};
struct bcm_sock {
struct sock sk;
@@ -453,16 +453,22 @@ static void bcm_send_to_user(struct bcm_op *op, struct bcm_msg_head *head,
static bool bcm_tx_set_expiry(struct bcm_op *op, struct hrtimer *hrt)
{
ktime_t ival;
+ spin_lock_bh(&op->bcm_tx_lock);
+
if (op->kt_ival1 && op->count)
ival = op->kt_ival1;
- else if (op->kt_ival2)
+ else if (op->kt_ival2) {
ival = op->kt_ival2;
- else
+ } else {
+ spin_unlock_bh(&op->bcm_tx_lock);
return false;
+ }
+
+ spin_unlock_bh(&op->bcm_tx_lock);
hrtimer_set_expires(hrt, ktime_add(ktime_get(), ival));
return true;
}
@@ -475,12 +481,21 @@ static void bcm_tx_start_timer(struct bcm_op *op)
/* bcm_tx_timeout_handler - performs cyclic CAN frame transmissions */
static enum hrtimer_restart bcm_tx_timeout_handler(struct hrtimer *hrtimer)
{
struct bcm_op *op = container_of(hrtimer, struct bcm_op, timer);
struct bcm_msg_head msg_head;
+ bool tx_ival1, tx_ival2;
- if (op->kt_ival1 && (op->count > 0)) {
+ /* snapshot kt_ival1/kt_ival2/count under lock to avoid torn
+ * ktime_t reads racing with concurrent bcm_tx_setup() updates
+ */
+ spin_lock_bh(&op->bcm_tx_lock);
+ tx_ival1 = op->kt_ival1 && (op->count > 0);
+ tx_ival2 = !!op->kt_ival2;
+ spin_unlock_bh(&op->bcm_tx_lock);
+
+ if (tx_ival1) {
bcm_can_tx(op, NULL);
if (!op->count && (op->flags & TX_COUNTEVT)) {
/* create notification to user */
memset(&msg_head, 0, sizeof(msg_head));
@@ -493,11 +508,11 @@ static enum hrtimer_restart bcm_tx_timeout_handler(struct hrtimer *hrtimer)
msg_head.nframes = 0;
bcm_send_to_user(op, &msg_head, NULL, 0);
}
- } else if (op->kt_ival2) {
+ } else if (tx_ival2) {
bcm_can_tx(op, NULL);
}
return bcm_tx_set_expiry(op, &op->timer) ?
HRTIMER_RESTART : HRTIMER_NORESTART;
@@ -1016,64 +1031,80 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
return -EINVAL;
/* check the given can_id */
op = bcm_find_op(&bo->tx_ops, msg_head, ifindex);
if (op) {
+ void *new_frames;
+
/* update existing BCM operation */
/*
* Do we need more space for the CAN frames than currently
* allocated? -> This is a _really_ unusual use-case and
* therefore (complexity / locking) it is not supported.
*/
if (msg_head->nframes > op->nframes)
return -E2BIG;
- /* update CAN frames content */
+ /* get new CAN frames content into a staging buffer before
+ * locking: validate and normalize the frames there so that
+ * bcm_can_tx() / bcm_tx_timeout_handler() never observe a
+ * partially updated or unvalidated frame in op->frames
+ */
+ new_frames = kmalloc(msg_head->nframes * op->cfsiz, GFP_KERNEL);
+ if (!new_frames)
+ return -ENOMEM;
+
for (i = 0; i < msg_head->nframes; i++) {
- cf = op->frames + op->cfsiz * i;
+ cf = new_frames + op->cfsiz * i;
err = memcpy_from_msg((u8 *)cf, msg, op->cfsiz);
+ if (err < 0) {
+ kfree(new_frames);
+ return err;
+ }
if (op->flags & CAN_FD_FRAME) {
if (cf->len > 64)
err = -EINVAL;
} else {
if (cf->len > 8)
err = -EINVAL;
}
- if (err < 0)
+ if (err < 0) {
+ kfree(new_frames);
return err;
+ }
if (msg_head->flags & TX_CP_CAN_ID) {
/* copy can_id into frame */
cf->can_id = msg_head->can_id;
}
}
+
+ spin_lock_bh(&op->bcm_tx_lock);
+
+ /* update CAN frames content */
+ memcpy(op->frames, new_frames, msg_head->nframes * op->cfsiz);
+
op->flags = msg_head->flags;
- /* only lock for unlikely count/nframes/currframe changes */
if (op->nframes != msg_head->nframes ||
- op->flags & TX_RESET_MULTI_IDX ||
- op->flags & SETTIMER) {
-
- spin_lock_bh(&op->bcm_tx_lock);
+ op->flags & TX_RESET_MULTI_IDX) {
+ /* potentially update changed nframes */
+ op->nframes = msg_head->nframes;
+ /* restart multiple frame transmission */
+ op->currframe = 0;
+ }
- if (op->nframes != msg_head->nframes ||
- op->flags & TX_RESET_MULTI_IDX) {
- /* potentially update changed nframes */
- op->nframes = msg_head->nframes;
- /* restart multiple frame transmission */
- op->currframe = 0;
- }
+ if (op->flags & SETTIMER)
+ op->count = msg_head->count;
- if (op->flags & SETTIMER)
- op->count = msg_head->count;
+ spin_unlock_bh(&op->bcm_tx_lock);
- spin_unlock_bh(&op->bcm_tx_lock);
- }
+ kfree(new_frames);
} else {
/* insert new BCM operation for the given can_id */
op = kzalloc(OPSIZ, GFP_KERNEL);
@@ -1145,14 +1176,16 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
} /* if ((op = bcm_find_op(&bo->tx_ops, msg_head->can_id, ifindex))) */
if (op->flags & SETTIMER) {
/* set timer values */
+ spin_lock_bh(&op->bcm_tx_lock);
op->ival1 = msg_head->ival1;
op->ival2 = msg_head->ival2;
op->kt_ival1 = bcm_timeval_to_ktime(msg_head->ival1);
op->kt_ival2 = bcm_timeval_to_ktime(msg_head->ival2);
+ spin_unlock_bh(&op->bcm_tx_lock);
/* disable an active timer due to zero values? */
if (!op->kt_ival1 && !op->kt_ival2)
hrtimer_cancel(&op->timer);
}
--
2.53.0
^ permalink raw reply related [flat|nested] 29+ messages in thread
* [PATCH v7 06/10] can: bcm: extend bcm_tx_lock usage for data and timer updates
@ 2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
0 siblings, 0 replies; 29+ messages in thread
From: Oliver Hartkopp via B4 Relay @ 2026-07-08 15:21 UTC (permalink / raw)
To: linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde
From: Oliver Hartkopp <socketcan@hartkopp.net>
Stage new CAN frame content for an existing tx op into a kmalloc()'d
buffer and validate it there, mirroring the approach already used in
bcm_rx_setup(). Only copy the validated data into op->frames while
holding op->bcm_tx_lock, so bcm_can_tx() and bcm_tx_timeout_handler()
can no longer observe a partially updated or unvalidated frame.
Add a missing error path for memcpy_from_msg() when copying CAN frame
data from userspace.
Also move the kt_ival1/kt_ival2/ival1/ival2 updates in bcm_tx_setup()
under op->bcm_tx_lock, and read kt_ival1/kt_ival2/count under the same
lock in bcm_tx_set_expiry() and bcm_tx_timeout_handler(), closing the
torn 64-bit ktime_t read on 32-bit platforms.
Fixes: c2aba69d0c36 ("can: bcm: add locking for bcm_op runtime updates")
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
net/can/bcm.c | 81 +++++++++++++++++++++++++++++++++++++++++------------------
1 file changed, 57 insertions(+), 24 deletions(-)
diff --git a/net/can/bcm.c b/net/can/bcm.c
index fca7c714cc52..fefa77045253 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -126,11 +126,11 @@ struct bcm_op {
void *last_frames;
struct canfd_frame sframe;
struct canfd_frame last_sframe;
struct sock *sk;
struct net_device *rx_reg_dev;
- spinlock_t bcm_tx_lock; /* protect currframe/count in runtime updates */
+ spinlock_t bcm_tx_lock; /* protect tx data and timer updates */
spinlock_t bcm_rx_update_lock; /* protect filter/timer data updates */
};
struct bcm_sock {
struct sock sk;
@@ -453,16 +453,22 @@ static void bcm_send_to_user(struct bcm_op *op, struct bcm_msg_head *head,
static bool bcm_tx_set_expiry(struct bcm_op *op, struct hrtimer *hrt)
{
ktime_t ival;
+ spin_lock_bh(&op->bcm_tx_lock);
+
if (op->kt_ival1 && op->count)
ival = op->kt_ival1;
- else if (op->kt_ival2)
+ else if (op->kt_ival2) {
ival = op->kt_ival2;
- else
+ } else {
+ spin_unlock_bh(&op->bcm_tx_lock);
return false;
+ }
+
+ spin_unlock_bh(&op->bcm_tx_lock);
hrtimer_set_expires(hrt, ktime_add(ktime_get(), ival));
return true;
}
@@ -475,12 +481,21 @@ static void bcm_tx_start_timer(struct bcm_op *op)
/* bcm_tx_timeout_handler - performs cyclic CAN frame transmissions */
static enum hrtimer_restart bcm_tx_timeout_handler(struct hrtimer *hrtimer)
{
struct bcm_op *op = container_of(hrtimer, struct bcm_op, timer);
struct bcm_msg_head msg_head;
+ bool tx_ival1, tx_ival2;
- if (op->kt_ival1 && (op->count > 0)) {
+ /* snapshot kt_ival1/kt_ival2/count under lock to avoid torn
+ * ktime_t reads racing with concurrent bcm_tx_setup() updates
+ */
+ spin_lock_bh(&op->bcm_tx_lock);
+ tx_ival1 = op->kt_ival1 && (op->count > 0);
+ tx_ival2 = !!op->kt_ival2;
+ spin_unlock_bh(&op->bcm_tx_lock);
+
+ if (tx_ival1) {
bcm_can_tx(op, NULL);
if (!op->count && (op->flags & TX_COUNTEVT)) {
/* create notification to user */
memset(&msg_head, 0, sizeof(msg_head));
@@ -493,11 +508,11 @@ static enum hrtimer_restart bcm_tx_timeout_handler(struct hrtimer *hrtimer)
msg_head.nframes = 0;
bcm_send_to_user(op, &msg_head, NULL, 0);
}
- } else if (op->kt_ival2) {
+ } else if (tx_ival2) {
bcm_can_tx(op, NULL);
}
return bcm_tx_set_expiry(op, &op->timer) ?
HRTIMER_RESTART : HRTIMER_NORESTART;
@@ -1016,64 +1031,80 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
return -EINVAL;
/* check the given can_id */
op = bcm_find_op(&bo->tx_ops, msg_head, ifindex);
if (op) {
+ void *new_frames;
+
/* update existing BCM operation */
/*
* Do we need more space for the CAN frames than currently
* allocated? -> This is a _really_ unusual use-case and
* therefore (complexity / locking) it is not supported.
*/
if (msg_head->nframes > op->nframes)
return -E2BIG;
- /* update CAN frames content */
+ /* get new CAN frames content into a staging buffer before
+ * locking: validate and normalize the frames there so that
+ * bcm_can_tx() / bcm_tx_timeout_handler() never observe a
+ * partially updated or unvalidated frame in op->frames
+ */
+ new_frames = kmalloc(msg_head->nframes * op->cfsiz, GFP_KERNEL);
+ if (!new_frames)
+ return -ENOMEM;
+
for (i = 0; i < msg_head->nframes; i++) {
- cf = op->frames + op->cfsiz * i;
+ cf = new_frames + op->cfsiz * i;
err = memcpy_from_msg((u8 *)cf, msg, op->cfsiz);
+ if (err < 0) {
+ kfree(new_frames);
+ return err;
+ }
if (op->flags & CAN_FD_FRAME) {
if (cf->len > 64)
err = -EINVAL;
} else {
if (cf->len > 8)
err = -EINVAL;
}
- if (err < 0)
+ if (err < 0) {
+ kfree(new_frames);
return err;
+ }
if (msg_head->flags & TX_CP_CAN_ID) {
/* copy can_id into frame */
cf->can_id = msg_head->can_id;
}
}
+
+ spin_lock_bh(&op->bcm_tx_lock);
+
+ /* update CAN frames content */
+ memcpy(op->frames, new_frames, msg_head->nframes * op->cfsiz);
+
op->flags = msg_head->flags;
- /* only lock for unlikely count/nframes/currframe changes */
if (op->nframes != msg_head->nframes ||
- op->flags & TX_RESET_MULTI_IDX ||
- op->flags & SETTIMER) {
-
- spin_lock_bh(&op->bcm_tx_lock);
+ op->flags & TX_RESET_MULTI_IDX) {
+ /* potentially update changed nframes */
+ op->nframes = msg_head->nframes;
+ /* restart multiple frame transmission */
+ op->currframe = 0;
+ }
- if (op->nframes != msg_head->nframes ||
- op->flags & TX_RESET_MULTI_IDX) {
- /* potentially update changed nframes */
- op->nframes = msg_head->nframes;
- /* restart multiple frame transmission */
- op->currframe = 0;
- }
+ if (op->flags & SETTIMER)
+ op->count = msg_head->count;
- if (op->flags & SETTIMER)
- op->count = msg_head->count;
+ spin_unlock_bh(&op->bcm_tx_lock);
- spin_unlock_bh(&op->bcm_tx_lock);
- }
+ kfree(new_frames);
} else {
/* insert new BCM operation for the given can_id */
op = kzalloc(OPSIZ, GFP_KERNEL);
@@ -1145,14 +1176,16 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
} /* if ((op = bcm_find_op(&bo->tx_ops, msg_head->can_id, ifindex))) */
if (op->flags & SETTIMER) {
/* set timer values */
+ spin_lock_bh(&op->bcm_tx_lock);
op->ival1 = msg_head->ival1;
op->ival2 = msg_head->ival2;
op->kt_ival1 = bcm_timeval_to_ktime(msg_head->ival1);
op->kt_ival2 = bcm_timeval_to_ktime(msg_head->ival2);
+ spin_unlock_bh(&op->bcm_tx_lock);
/* disable an active timer due to zero values? */
if (!op->kt_ival1 && !op->kt_ival2)
hrtimer_cancel(&op->timer);
}
--
2.53.0
^ permalink raw reply related [flat|nested] 29+ messages in thread
* [PATCH v7 07/10] can: bcm: validate frame length in bcm_rx_setup() for RTR replies
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
@ 2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
-1 siblings, 0 replies; 29+ messages in thread
From: Oliver Hartkopp @ 2026-07-08 15:21 UTC (permalink / raw)
To: linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde
bcm_tx_setup() validates cf->len against the CAN/CAN FD DLC limits
before installing frames for TX_SETUP, but bcm_rx_setup() never did
the same for the RTR-reply frame configured via RX_SETUP with
RX_RTR_FRAME.
Fixes: ffd980f976e7 ("[CAN]: Add broadcast manager (bcm) protocol")
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
net/can/bcm.c | 59 +++++++++++++++++++++++++++++++++++++++++------------------
1 file changed, 41 insertions(+), 18 deletions(-)
diff --git a/net/can/bcm.c b/net/can/bcm.c
index fefa77045253..300f1f88c4d2 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -1213,26 +1213,41 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
kfree(op->frames);
kfree(op);
return err;
}
-static void bcm_rx_setup_rtr_check(struct bcm_msg_head *msg_head,
- struct bcm_op *op, void *new_frames)
+static int bcm_rx_setup_rtr_check(struct bcm_msg_head *msg_head,
+ struct bcm_op *op, void *new_frames)
{
+ struct canfd_frame *frame0 = new_frames;
+
+ if (!(msg_head->flags & RX_RTR_FRAME))
+ return 0;
+
+ /* this frame is sent out as-is by bcm_can_tx() whenever a matching
+ * remote request is received, so validate its length the same way
+ * bcm_tx_setup() validates TX_SETUP frames before installing it
+ */
+ if (msg_head->flags & CAN_FD_FRAME) {
+ if (frame0->len > 64)
+ return -EINVAL;
+ } else {
+ if (frame0->len > 8)
+ return -EINVAL;
+ }
+
/* funny feature in RX(!)_SETUP only for RTR-mode:
* copy can_id into frame BUT without RTR-flag to
* prevent a full-load-loopback-test ... ;-]
* normalize this on the staged buffer, before it is
* ever installed into op->frames.
*/
- if (msg_head->flags & RX_RTR_FRAME) {
- struct canfd_frame *frame0 = new_frames;
+ if ((msg_head->flags & TX_CP_CAN_ID) ||
+ frame0->can_id == op->can_id)
+ frame0->can_id = op->can_id & ~CAN_RTR_FLAG;
- if ((msg_head->flags & TX_CP_CAN_ID) ||
- frame0->can_id == op->can_id)
- frame0->can_id = op->can_id & ~CAN_RTR_FLAG;
- }
+ return 0;
}
/*
* bcm_rx_setup - create or update a bcm rx op (for bcm_sendmsg)
*/
@@ -1291,11 +1306,15 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
if (err < 0) {
kfree(new_frames);
return err;
}
- bcm_rx_setup_rtr_check(msg_head, op, new_frames);
+ err = bcm_rx_setup_rtr_check(msg_head, op, new_frames);
+ if (err < 0) {
+ kfree(new_frames);
+ return err;
+ }
}
spin_lock_bh(&op->bcm_rx_update_lock);
op->nframes = msg_head->nframes;
op->flags = msg_head->flags;
@@ -1356,20 +1375,16 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
}
if (msg_head->nframes) {
err = memcpy_from_msg(op->frames, msg,
msg_head->nframes * op->cfsiz);
- if (err < 0) {
- if (op->frames != &op->sframe)
- kfree(op->frames);
- if (op->last_frames != &op->last_sframe)
- kfree(op->last_frames);
- kfree(op);
- return err;
- }
+ if (err < 0)
+ goto free_op;
- bcm_rx_setup_rtr_check(msg_head, op, op->frames);
+ err = bcm_rx_setup_rtr_check(msg_head, op, op->frames);
+ if (err < 0)
+ goto free_op;
}
/* bcm_can_tx / bcm_tx_timeout_handler needs this */
op->sk = sk;
sock_hold(sk);
@@ -1462,10 +1477,18 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
/* add this bcm_op to the list of the rx_ops */
list_add_rcu(&op->list, &bo->rx_ops);
}
return msg_head->nframes * op->cfsiz + MHSIZ;
+
+free_op:
+ if (op->frames != &op->sframe)
+ kfree(op->frames);
+ if (op->last_frames != &op->last_sframe)
+ kfree(op->last_frames);
+ kfree(op);
+ return err;
}
/*
* bcm_tx_send - send a single CAN frame to the CAN interface (for bcm_sendmsg)
*/
--
2.53.0
^ permalink raw reply related [flat|nested] 29+ messages in thread
* [PATCH v7 07/10] can: bcm: validate frame length in bcm_rx_setup() for RTR replies
@ 2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
0 siblings, 0 replies; 29+ messages in thread
From: Oliver Hartkopp via B4 Relay @ 2026-07-08 15:21 UTC (permalink / raw)
To: linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde
From: Oliver Hartkopp <socketcan@hartkopp.net>
bcm_tx_setup() validates cf->len against the CAN/CAN FD DLC limits
before installing frames for TX_SETUP, but bcm_rx_setup() never did
the same for the RTR-reply frame configured via RX_SETUP with
RX_RTR_FRAME.
Fixes: ffd980f976e7 ("[CAN]: Add broadcast manager (bcm) protocol")
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
net/can/bcm.c | 59 +++++++++++++++++++++++++++++++++++++++++------------------
1 file changed, 41 insertions(+), 18 deletions(-)
diff --git a/net/can/bcm.c b/net/can/bcm.c
index fefa77045253..300f1f88c4d2 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -1213,26 +1213,41 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
kfree(op->frames);
kfree(op);
return err;
}
-static void bcm_rx_setup_rtr_check(struct bcm_msg_head *msg_head,
- struct bcm_op *op, void *new_frames)
+static int bcm_rx_setup_rtr_check(struct bcm_msg_head *msg_head,
+ struct bcm_op *op, void *new_frames)
{
+ struct canfd_frame *frame0 = new_frames;
+
+ if (!(msg_head->flags & RX_RTR_FRAME))
+ return 0;
+
+ /* this frame is sent out as-is by bcm_can_tx() whenever a matching
+ * remote request is received, so validate its length the same way
+ * bcm_tx_setup() validates TX_SETUP frames before installing it
+ */
+ if (msg_head->flags & CAN_FD_FRAME) {
+ if (frame0->len > 64)
+ return -EINVAL;
+ } else {
+ if (frame0->len > 8)
+ return -EINVAL;
+ }
+
/* funny feature in RX(!)_SETUP only for RTR-mode:
* copy can_id into frame BUT without RTR-flag to
* prevent a full-load-loopback-test ... ;-]
* normalize this on the staged buffer, before it is
* ever installed into op->frames.
*/
- if (msg_head->flags & RX_RTR_FRAME) {
- struct canfd_frame *frame0 = new_frames;
+ if ((msg_head->flags & TX_CP_CAN_ID) ||
+ frame0->can_id == op->can_id)
+ frame0->can_id = op->can_id & ~CAN_RTR_FLAG;
- if ((msg_head->flags & TX_CP_CAN_ID) ||
- frame0->can_id == op->can_id)
- frame0->can_id = op->can_id & ~CAN_RTR_FLAG;
- }
+ return 0;
}
/*
* bcm_rx_setup - create or update a bcm rx op (for bcm_sendmsg)
*/
@@ -1291,11 +1306,15 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
if (err < 0) {
kfree(new_frames);
return err;
}
- bcm_rx_setup_rtr_check(msg_head, op, new_frames);
+ err = bcm_rx_setup_rtr_check(msg_head, op, new_frames);
+ if (err < 0) {
+ kfree(new_frames);
+ return err;
+ }
}
spin_lock_bh(&op->bcm_rx_update_lock);
op->nframes = msg_head->nframes;
op->flags = msg_head->flags;
@@ -1356,20 +1375,16 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
}
if (msg_head->nframes) {
err = memcpy_from_msg(op->frames, msg,
msg_head->nframes * op->cfsiz);
- if (err < 0) {
- if (op->frames != &op->sframe)
- kfree(op->frames);
- if (op->last_frames != &op->last_sframe)
- kfree(op->last_frames);
- kfree(op);
- return err;
- }
+ if (err < 0)
+ goto free_op;
- bcm_rx_setup_rtr_check(msg_head, op, op->frames);
+ err = bcm_rx_setup_rtr_check(msg_head, op, op->frames);
+ if (err < 0)
+ goto free_op;
}
/* bcm_can_tx / bcm_tx_timeout_handler needs this */
op->sk = sk;
sock_hold(sk);
@@ -1462,10 +1477,18 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
/* add this bcm_op to the list of the rx_ops */
list_add_rcu(&op->list, &bo->rx_ops);
}
return msg_head->nframes * op->cfsiz + MHSIZ;
+
+free_op:
+ if (op->frames != &op->sframe)
+ kfree(op->frames);
+ if (op->last_frames != &op->last_sframe)
+ kfree(op->last_frames);
+ kfree(op);
+ return err;
}
/*
* bcm_tx_send - send a single CAN frame to the CAN interface (for bcm_sendmsg)
*/
--
2.53.0
^ permalink raw reply related [flat|nested] 29+ messages in thread
* [PATCH v7 08/10] can: bcm: add missing device refcount for CAN filter removal
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
@ 2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
-1 siblings, 0 replies; 29+ messages in thread
From: Oliver Hartkopp @ 2026-07-08 15:21 UTC (permalink / raw)
To: linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde, sashiko-bot
sashiko-bot remarked a problem with a concurrent device unregistration
in isotp.c which also is present in the bcm.c code. A former fix for raw.c
commit c275a176e4b6 ("can: raw: add missing refcount for memory leak fix")
introduced a netdevice_tracker which solves the issue for bcm.c too.
bcm_release(), bcm_delete_rx_op() and bcm_notifier() relied on
dev_get_by_index(ifindex) to re-find the device for an rx_op before
unregistering its filter. If a concurrent NETDEV_UNREGISTER has already
unlisted the device from the ifindex table, that lookup fails and
can_rx_unregister() is silently skipped, leaving a stale CAN filter
pointing at the soon-to-be-freed bcm_op/socket.
Hold a netdev_hold()/netdev_put() tracked reference on op->rx_reg_dev
from the moment the rx filter is registered in bcm_rx_setup() until it
is unregistered in bcm_rx_unreg(), and use that reference directly in
bcm_release() and bcm_delete_rx_op() instead of re-looking the device
up by ifindex.
Reported-by: sashiko-bot@kernel.org
Link: https://sashiko.dev/#/patchset/20260707094716.63578-1-socketcan@hartkopp.net
Fixes: ffd980f976e7 ("[CAN]: Add broadcast manager (bcm) protocol")
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
net/can/bcm.c | 47 +++++++++++++++++++++++++++--------------------
1 file changed, 27 insertions(+), 20 deletions(-)
diff --git a/net/can/bcm.c b/net/can/bcm.c
index 300f1f88c4d2..4bdca72f9327 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -126,10 +126,11 @@ struct bcm_op {
void *last_frames;
struct canfd_frame sframe;
struct canfd_frame last_sframe;
struct sock *sk;
struct net_device *rx_reg_dev;
+ netdevice_tracker rx_reg_dev_tracker;
spinlock_t bcm_tx_lock; /* protect tx data and timer updates */
spinlock_t bcm_rx_update_lock; /* protect filter/timer data updates */
};
struct bcm_sock {
@@ -904,10 +905,11 @@ static void bcm_rx_unreg(struct net_device *dev, struct bcm_op *op)
can_rx_unregister(dev_net(dev), dev, op->can_id,
REGMASK(op->can_id), bcm_rx_handler, op);
/* mark as removed subscription */
op->rx_reg_dev = NULL;
+ netdev_put(dev, &op->rx_reg_dev_tracker);
} else
printk(KERN_ERR "can-bcm: bcm_rx_unreg: registered device "
"mismatch %p %p\n", op->rx_reg_dev, dev);
}
@@ -934,21 +936,18 @@ static int bcm_delete_rx_op(struct list_head *ops, struct bcm_msg_head *mh,
if (op->ifindex) {
/*
* Only remove subscriptions that had not
* been removed due to NETDEV_UNREGISTER
* in bcm_notifier()
+ *
+ * op->rx_reg_dev is a tracked reference taken
+ * when the subscription was registered, so it
+ * stays valid here even if a concurrent
+ * NETDEV_UNREGISTER already unlisted the dev.
*/
- if (op->rx_reg_dev) {
- struct net_device *dev;
-
- dev = dev_get_by_index(sock_net(op->sk),
- op->ifindex);
- if (dev) {
- bcm_rx_unreg(dev, op);
- dev_put(dev);
- }
- }
+ if (op->rx_reg_dev)
+ bcm_rx_unreg(op->rx_reg_dev, op);
} else
can_rx_unregister(sock_net(op->sk), NULL,
op->can_id,
REGMASK(op->can_id),
bcm_rx_handler, op);
@@ -1453,11 +1452,21 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
op->can_id,
REGMASK(op->can_id),
bcm_rx_handler, op,
"bcm", sk);
- op->rx_reg_dev = dev;
+ /* keep a tracked reference so that a later
+ * unregister can safely reach the device even
+ * if a concurrent NETDEV_UNREGISTER has
+ * already unlisted it by ifindex
+ */
+ if (!err) {
+ op->rx_reg_dev = dev;
+ netdev_hold(dev,
+ &op->rx_reg_dev_tracker,
+ GFP_KERNEL);
+ }
dev_put(dev);
} else {
/* the requested device is gone - do not
* silently succeed without registering
*/
@@ -1830,20 +1839,18 @@ static int bcm_release(struct socket *sock)
if (op->ifindex) {
/*
* Only remove subscriptions that had not
* been removed due to NETDEV_UNREGISTER
* in bcm_notifier()
+ *
+ * op->rx_reg_dev is a tracked reference taken
+ * when the subscription was registered, so it
+ * stays valid here even if a concurrent
+ * NETDEV_UNREGISTER already unlisted the device.
*/
- if (op->rx_reg_dev) {
- struct net_device *dev;
-
- dev = dev_get_by_index(net, op->ifindex);
- if (dev) {
- bcm_rx_unreg(dev, op);
- dev_put(dev);
- }
- }
+ if (op->rx_reg_dev)
+ bcm_rx_unreg(op->rx_reg_dev, op);
} else
can_rx_unregister(net, NULL, op->can_id,
REGMASK(op->can_id),
bcm_rx_handler, op);
--
2.53.0
^ permalink raw reply related [flat|nested] 29+ messages in thread
* [PATCH v7 08/10] can: bcm: add missing device refcount for CAN filter removal
@ 2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
0 siblings, 0 replies; 29+ messages in thread
From: Oliver Hartkopp via B4 Relay @ 2026-07-08 15:21 UTC (permalink / raw)
To: linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde, sashiko-bot
From: Oliver Hartkopp <socketcan@hartkopp.net>
sashiko-bot remarked a problem with a concurrent device unregistration
in isotp.c which also is present in the bcm.c code. A former fix for raw.c
commit c275a176e4b6 ("can: raw: add missing refcount for memory leak fix")
introduced a netdevice_tracker which solves the issue for bcm.c too.
bcm_release(), bcm_delete_rx_op() and bcm_notifier() relied on
dev_get_by_index(ifindex) to re-find the device for an rx_op before
unregistering its filter. If a concurrent NETDEV_UNREGISTER has already
unlisted the device from the ifindex table, that lookup fails and
can_rx_unregister() is silently skipped, leaving a stale CAN filter
pointing at the soon-to-be-freed bcm_op/socket.
Hold a netdev_hold()/netdev_put() tracked reference on op->rx_reg_dev
from the moment the rx filter is registered in bcm_rx_setup() until it
is unregistered in bcm_rx_unreg(), and use that reference directly in
bcm_release() and bcm_delete_rx_op() instead of re-looking the device
up by ifindex.
Reported-by: sashiko-bot@kernel.org
Link: https://sashiko.dev/#/patchset/20260707094716.63578-1-socketcan@hartkopp.net
Fixes: ffd980f976e7 ("[CAN]: Add broadcast manager (bcm) protocol")
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
net/can/bcm.c | 47 +++++++++++++++++++++++++++--------------------
1 file changed, 27 insertions(+), 20 deletions(-)
diff --git a/net/can/bcm.c b/net/can/bcm.c
index 300f1f88c4d2..4bdca72f9327 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -126,10 +126,11 @@ struct bcm_op {
void *last_frames;
struct canfd_frame sframe;
struct canfd_frame last_sframe;
struct sock *sk;
struct net_device *rx_reg_dev;
+ netdevice_tracker rx_reg_dev_tracker;
spinlock_t bcm_tx_lock; /* protect tx data and timer updates */
spinlock_t bcm_rx_update_lock; /* protect filter/timer data updates */
};
struct bcm_sock {
@@ -904,10 +905,11 @@ static void bcm_rx_unreg(struct net_device *dev, struct bcm_op *op)
can_rx_unregister(dev_net(dev), dev, op->can_id,
REGMASK(op->can_id), bcm_rx_handler, op);
/* mark as removed subscription */
op->rx_reg_dev = NULL;
+ netdev_put(dev, &op->rx_reg_dev_tracker);
} else
printk(KERN_ERR "can-bcm: bcm_rx_unreg: registered device "
"mismatch %p %p\n", op->rx_reg_dev, dev);
}
@@ -934,21 +936,18 @@ static int bcm_delete_rx_op(struct list_head *ops, struct bcm_msg_head *mh,
if (op->ifindex) {
/*
* Only remove subscriptions that had not
* been removed due to NETDEV_UNREGISTER
* in bcm_notifier()
+ *
+ * op->rx_reg_dev is a tracked reference taken
+ * when the subscription was registered, so it
+ * stays valid here even if a concurrent
+ * NETDEV_UNREGISTER already unlisted the dev.
*/
- if (op->rx_reg_dev) {
- struct net_device *dev;
-
- dev = dev_get_by_index(sock_net(op->sk),
- op->ifindex);
- if (dev) {
- bcm_rx_unreg(dev, op);
- dev_put(dev);
- }
- }
+ if (op->rx_reg_dev)
+ bcm_rx_unreg(op->rx_reg_dev, op);
} else
can_rx_unregister(sock_net(op->sk), NULL,
op->can_id,
REGMASK(op->can_id),
bcm_rx_handler, op);
@@ -1453,11 +1452,21 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
op->can_id,
REGMASK(op->can_id),
bcm_rx_handler, op,
"bcm", sk);
- op->rx_reg_dev = dev;
+ /* keep a tracked reference so that a later
+ * unregister can safely reach the device even
+ * if a concurrent NETDEV_UNREGISTER has
+ * already unlisted it by ifindex
+ */
+ if (!err) {
+ op->rx_reg_dev = dev;
+ netdev_hold(dev,
+ &op->rx_reg_dev_tracker,
+ GFP_KERNEL);
+ }
dev_put(dev);
} else {
/* the requested device is gone - do not
* silently succeed without registering
*/
@@ -1830,20 +1839,18 @@ static int bcm_release(struct socket *sock)
if (op->ifindex) {
/*
* Only remove subscriptions that had not
* been removed due to NETDEV_UNREGISTER
* in bcm_notifier()
+ *
+ * op->rx_reg_dev is a tracked reference taken
+ * when the subscription was registered, so it
+ * stays valid here even if a concurrent
+ * NETDEV_UNREGISTER already unlisted the device.
*/
- if (op->rx_reg_dev) {
- struct net_device *dev;
-
- dev = dev_get_by_index(net, op->ifindex);
- if (dev) {
- bcm_rx_unreg(dev, op);
- dev_put(dev);
- }
- }
+ if (op->rx_reg_dev)
+ bcm_rx_unreg(op->rx_reg_dev, op);
} else
can_rx_unregister(net, NULL, op->can_id,
REGMASK(op->can_id),
bcm_rx_handler, op);
--
2.53.0
^ permalink raw reply related [flat|nested] 29+ messages in thread
* [PATCH v7 09/10] can: bcm: fix stale rx/tx ops after device removal
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
@ 2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
-1 siblings, 0 replies; 29+ messages in thread
From: Oliver Hartkopp @ 2026-07-08 15:21 UTC (permalink / raw)
To: linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde, sashiko-bot
RX: an RX_SETUP update(!) for an existing op skipped can_rx_register()
unconditionally, even when a concurrent NETDEV_UNREGISTER had already
torn down its registration (op->rx_reg_dev == NULL). This silently
did not re-enable frame delivery for that updated filter with no error
reported to userspace. bcm_rx_setup() now re-registers in that case,
while leaving rx_ops with ifindex = 0 (all CAN interfaces) which never
carry a tracked rx_reg_dev registered as-is.
TX: bcm_notify() only handled bo->rx_ops on NETDEV_UNREGISTER, leaving
tx_ops with a dead ifindex untouched. bcm_tx_timeout_handler() kept
re-arming its hrtimer indefinitely, and if the ifindex was later
reused by a different CAN device, bcm_can_tx() would silently transmit
the cyclic frames to that unrelated device. bcm_notify() now stops the
timer and clears op->ifindex for affected tx_ops, without removing the
tx_op itself, so that a later TX_SETUP update can reconfigure it.
Reported-by: sashiko-bot@kernel.org
Link: https://lore.kernel.org/linux-can/20260708094536.DDF821F00A3A@smtp.kernel.org/
Fixes: ffd980f976e7 ("[CAN]: Add broadcast manager (bcm) protocol")
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
net/can/bcm.c | 45 +++++++++++++++++++++++++++++++++++++--------
1 file changed, 37 insertions(+), 8 deletions(-)
diff --git a/net/can/bcm.c b/net/can/bcm.c
index 4bdca72f9327..9d0193170808 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -1254,10 +1254,11 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
int ifindex, struct sock *sk)
{
struct bcm_sock *bo = bcm_sk(sk);
struct bcm_op *op;
int do_rx_register;
+ int new_op = 0;
int err = 0;
if ((msg_head->flags & RX_FILTER_ID) || (!(msg_head->nframes))) {
/* be robust against wrong usage ... */
msg_head->flags |= RX_FILTER_ID;
@@ -1330,12 +1331,19 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
spin_unlock_bh(&op->bcm_rx_update_lock);
/* free temporary frames / kfree(NULL) is safe */
kfree(new_frames);
- /* Only an update -> do not call can_rx_register() */
- do_rx_register = 0;
+ /* Don't register a new CAN filter for the rx_op update unless
+ * a concurrent NETDEV_UNREGISTER notifier already tore down
+ * the previous registration. In this case the receiver needs
+ * to be re-registered here so that this update doesn't
+ * silently stop delivering frames for the given ifindex.
+ * Ops with ifindex = 0 (all CAN interfaces) never carry a
+ * tracked rx_reg_dev and stay registered as-is.
+ */
+ do_rx_register = (ifindex && !op->rx_reg_dev) ? 1 : 0;
} else {
/* insert new BCM operation for the given can_id */
op = kzalloc(OPSIZ, GFP_KERNEL);
if (!op)
@@ -1398,10 +1406,11 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
hrtimer_setup(&op->thrtimer, bcm_rx_thr_handler, CLOCK_MONOTONIC,
HRTIMER_MODE_REL_SOFT);
/* call can_rx_register() */
do_rx_register = 1;
+ new_op = 1;
} /* if ((op = bcm_find_op(&bo->rx_ops, msg_head->can_id, ifindex))) */
/* check flags */
@@ -1439,11 +1448,14 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
if ((op->flags & STARTTIMER) && op->kt_ival1)
hrtimer_start(&op->timer, op->kt_ival1,
HRTIMER_MODE_REL_SOFT);
}
- /* now we can register for can_ids, if we added a new bcm_op */
+ /* now we can register for can_ids, if we added a new bcm_op
+ * or need to re-register after a NETDEV_UNREGISTER tore down
+ * the previous registration of an existing op
+ */
if (do_rx_register) {
if (ifindex) {
struct net_device *dev;
dev = dev_get_by_index(sock_net(sk), ifindex);
@@ -1471,22 +1483,25 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
* silently succeed without registering
*/
err = -ENODEV;
}
- } else
+ } else {
err = can_rx_register(sock_net(sk), NULL, op->can_id,
REGMASK(op->can_id),
bcm_rx_handler, op, "bcm", sk);
- if (err) {
+ }
+
+ if (err && new_op) {
/* this bcm rx op is broken -> remove it */
bcm_remove_op(op);
return err;
}
- /* add this bcm_op to the list of the rx_ops */
- list_add_rcu(&op->list, &bo->rx_ops);
+ /* add a new bcm_op to the list of the rx_ops */
+ if (new_op)
+ list_add_rcu(&op->list, &bo->rx_ops);
}
return msg_head->nframes * op->cfsiz + MHSIZ;
free_op:
@@ -1702,15 +1717,29 @@ static void bcm_notify(struct bcm_sock *bo, unsigned long msg,
switch (msg) {
case NETDEV_UNREGISTER:
lock_sock(sk);
- /* remove device specific receive entries */
+ /* rx_ops: remove device specific receive entries */
list_for_each_entry(op, &bo->rx_ops, list)
if (op->rx_reg_dev == dev)
bcm_rx_unreg(dev, op);
+ /* tx_ops: stop device specific cyclic transmissions on the
+ * vanishing ifindex and invalidate the op->ifindex.
+ */
+ list_for_each_entry(op, &bo->tx_ops, list) {
+ if (op->ifindex != dev->ifindex)
+ continue;
+
+ spin_lock_bh(&op->bcm_tx_lock);
+ op->ifindex = 0;
+ spin_unlock_bh(&op->bcm_tx_lock);
+
+ hrtimer_cancel(&op->timer);
+ }
+
/* remove device reference, if this is our bound device */
if (bo->bound && bo->ifindex == dev->ifindex) {
#if IS_ENABLED(CONFIG_PROC_FS)
if (sock_net(sk)->can.bcmproc_dir && bo->bcm_proc_read) {
remove_proc_entry(bo->procname, sock_net(sk)->can.bcmproc_dir);
--
2.53.0
^ permalink raw reply related [flat|nested] 29+ messages in thread
* [PATCH v7 09/10] can: bcm: fix stale rx/tx ops after device removal
@ 2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
0 siblings, 0 replies; 29+ messages in thread
From: Oliver Hartkopp via B4 Relay @ 2026-07-08 15:21 UTC (permalink / raw)
To: linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde, sashiko-bot
From: Oliver Hartkopp <socketcan@hartkopp.net>
RX: an RX_SETUP update(!) for an existing op skipped can_rx_register()
unconditionally, even when a concurrent NETDEV_UNREGISTER had already
torn down its registration (op->rx_reg_dev == NULL). This silently
did not re-enable frame delivery for that updated filter with no error
reported to userspace. bcm_rx_setup() now re-registers in that case,
while leaving rx_ops with ifindex = 0 (all CAN interfaces) which never
carry a tracked rx_reg_dev registered as-is.
TX: bcm_notify() only handled bo->rx_ops on NETDEV_UNREGISTER, leaving
tx_ops with a dead ifindex untouched. bcm_tx_timeout_handler() kept
re-arming its hrtimer indefinitely, and if the ifindex was later
reused by a different CAN device, bcm_can_tx() would silently transmit
the cyclic frames to that unrelated device. bcm_notify() now stops the
timer and clears op->ifindex for affected tx_ops, without removing the
tx_op itself, so that a later TX_SETUP update can reconfigure it.
Reported-by: sashiko-bot@kernel.org
Link: https://lore.kernel.org/linux-can/20260708094536.DDF821F00A3A@smtp.kernel.org/
Fixes: ffd980f976e7 ("[CAN]: Add broadcast manager (bcm) protocol")
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
net/can/bcm.c | 45 +++++++++++++++++++++++++++++++++++++--------
1 file changed, 37 insertions(+), 8 deletions(-)
diff --git a/net/can/bcm.c b/net/can/bcm.c
index 4bdca72f9327..9d0193170808 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -1254,10 +1254,11 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
int ifindex, struct sock *sk)
{
struct bcm_sock *bo = bcm_sk(sk);
struct bcm_op *op;
int do_rx_register;
+ int new_op = 0;
int err = 0;
if ((msg_head->flags & RX_FILTER_ID) || (!(msg_head->nframes))) {
/* be robust against wrong usage ... */
msg_head->flags |= RX_FILTER_ID;
@@ -1330,12 +1331,19 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
spin_unlock_bh(&op->bcm_rx_update_lock);
/* free temporary frames / kfree(NULL) is safe */
kfree(new_frames);
- /* Only an update -> do not call can_rx_register() */
- do_rx_register = 0;
+ /* Don't register a new CAN filter for the rx_op update unless
+ * a concurrent NETDEV_UNREGISTER notifier already tore down
+ * the previous registration. In this case the receiver needs
+ * to be re-registered here so that this update doesn't
+ * silently stop delivering frames for the given ifindex.
+ * Ops with ifindex = 0 (all CAN interfaces) never carry a
+ * tracked rx_reg_dev and stay registered as-is.
+ */
+ do_rx_register = (ifindex && !op->rx_reg_dev) ? 1 : 0;
} else {
/* insert new BCM operation for the given can_id */
op = kzalloc(OPSIZ, GFP_KERNEL);
if (!op)
@@ -1398,10 +1406,11 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
hrtimer_setup(&op->thrtimer, bcm_rx_thr_handler, CLOCK_MONOTONIC,
HRTIMER_MODE_REL_SOFT);
/* call can_rx_register() */
do_rx_register = 1;
+ new_op = 1;
} /* if ((op = bcm_find_op(&bo->rx_ops, msg_head->can_id, ifindex))) */
/* check flags */
@@ -1439,11 +1448,14 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
if ((op->flags & STARTTIMER) && op->kt_ival1)
hrtimer_start(&op->timer, op->kt_ival1,
HRTIMER_MODE_REL_SOFT);
}
- /* now we can register for can_ids, if we added a new bcm_op */
+ /* now we can register for can_ids, if we added a new bcm_op
+ * or need to re-register after a NETDEV_UNREGISTER tore down
+ * the previous registration of an existing op
+ */
if (do_rx_register) {
if (ifindex) {
struct net_device *dev;
dev = dev_get_by_index(sock_net(sk), ifindex);
@@ -1471,22 +1483,25 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
* silently succeed without registering
*/
err = -ENODEV;
}
- } else
+ } else {
err = can_rx_register(sock_net(sk), NULL, op->can_id,
REGMASK(op->can_id),
bcm_rx_handler, op, "bcm", sk);
- if (err) {
+ }
+
+ if (err && new_op) {
/* this bcm rx op is broken -> remove it */
bcm_remove_op(op);
return err;
}
- /* add this bcm_op to the list of the rx_ops */
- list_add_rcu(&op->list, &bo->rx_ops);
+ /* add a new bcm_op to the list of the rx_ops */
+ if (new_op)
+ list_add_rcu(&op->list, &bo->rx_ops);
}
return msg_head->nframes * op->cfsiz + MHSIZ;
free_op:
@@ -1702,15 +1717,29 @@ static void bcm_notify(struct bcm_sock *bo, unsigned long msg,
switch (msg) {
case NETDEV_UNREGISTER:
lock_sock(sk);
- /* remove device specific receive entries */
+ /* rx_ops: remove device specific receive entries */
list_for_each_entry(op, &bo->rx_ops, list)
if (op->rx_reg_dev == dev)
bcm_rx_unreg(dev, op);
+ /* tx_ops: stop device specific cyclic transmissions on the
+ * vanishing ifindex and invalidate the op->ifindex.
+ */
+ list_for_each_entry(op, &bo->tx_ops, list) {
+ if (op->ifindex != dev->ifindex)
+ continue;
+
+ spin_lock_bh(&op->bcm_tx_lock);
+ op->ifindex = 0;
+ spin_unlock_bh(&op->bcm_tx_lock);
+
+ hrtimer_cancel(&op->timer);
+ }
+
/* remove device reference, if this is our bound device */
if (bo->bound && bo->ifindex == dev->ifindex) {
#if IS_ENABLED(CONFIG_PROC_FS)
if (sock_net(sk)->can.bcmproc_dir && bo->bcm_proc_read) {
remove_proc_entry(bo->procname, sock_net(sk)->can.bcmproc_dir);
--
2.53.0
^ permalink raw reply related [flat|nested] 29+ messages in thread
* [PATCH v7 10/10] can: bcm: fix data race on rx_stamp/rx_ifindex in bcm_rx_handler()
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
@ 2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
-1 siblings, 0 replies; 29+ messages in thread
From: Oliver Hartkopp @ 2026-07-08 15:21 UTC (permalink / raw)
To: linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde, sashiko-bot
For an rx op subscribed on all interfaces (ifindex == 0), the same op
is registered once in the shared per-netns wildcard filter list, so
bcm_rx_handler() can run concurrently on different CPUs for frames
arriving on different net devices.
op->rx_stamp and op->rx_ifindex were written before bcm_rx_update_lock was
taken, allowing concurrent writers to race each other - including a torn
store of the 64-bit rx_stamp on 32-bit platforms.
Beyond a torn store bcm_send_to_user() must report the timestamp/ifindex
of the very same frame whose content it is delivering. So the assignment
is placed in the same unbroken bcm_rx_update_lock section as the content
comparison.
As a side effect, the RTR-request frame feature (which never reach
bcm_send_to_user()) no longer updates rx_stamp/rx_ifindex, since only
the notification path needs them.
Fixes: ffd980f976e7 ("[CAN]: Add broadcast manager (bcm) protocol")
Reported-by: sashiko-bot@kernel.org
Link: https://lore.kernel.org/linux-can/20260707145135.5BC831F00A3A@smtp.kernel.org/
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
net/can/bcm.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/net/can/bcm.c b/net/can/bcm.c
index 9d0193170808..5591a0aed152 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -768,15 +768,10 @@ static void bcm_rx_handler(struct sk_buff *skb, void *data)
}
/* disable timeout */
hrtimer_cancel(&op->timer);
- /* save rx timestamp */
- op->rx_stamp = skb->tstamp;
- /* save originator for recvfrom() */
- op->rx_ifindex = skb->dev->ifindex;
-
/* snapshot RTR content under lock: op->flags/op->frames may be
* updated concurrently by bcm_rx_setup().
*/
spin_lock_bh(&op->bcm_rx_update_lock);
@@ -803,10 +798,18 @@ static void bcm_rx_handler(struct sk_buff *skb, void *data)
traffic_flags |= RX_OWN;
}
spin_lock_bh(&op->bcm_rx_update_lock);
+ /* save rx timestamp and originator for recvfrom() under lock.
+ * For an op subscribed on all interfaces (ifindex == 0)
+ * bcm_rx_handler() can run concurrently on different CPUs so
+ * the CAN content and the meta data must be bundled correctly.
+ */
+ op->rx_stamp = skb->tstamp;
+ op->rx_ifindex = skb->dev->ifindex;
+
if (op->flags & RX_FILTER_ID) {
/* the easiest case */
bcm_rx_update_and_send(op, op->last_frames, rxframe,
traffic_flags);
goto rx_starttimer;
--
2.53.0
^ permalink raw reply related [flat|nested] 29+ messages in thread
* [PATCH v7 10/10] can: bcm: fix data race on rx_stamp/rx_ifindex in bcm_rx_handler()
@ 2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
0 siblings, 0 replies; 29+ messages in thread
From: Oliver Hartkopp via B4 Relay @ 2026-07-08 15:21 UTC (permalink / raw)
To: linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde, sashiko-bot
From: Oliver Hartkopp <socketcan@hartkopp.net>
For an rx op subscribed on all interfaces (ifindex == 0), the same op
is registered once in the shared per-netns wildcard filter list, so
bcm_rx_handler() can run concurrently on different CPUs for frames
arriving on different net devices.
op->rx_stamp and op->rx_ifindex were written before bcm_rx_update_lock was
taken, allowing concurrent writers to race each other - including a torn
store of the 64-bit rx_stamp on 32-bit platforms.
Beyond a torn store bcm_send_to_user() must report the timestamp/ifindex
of the very same frame whose content it is delivering. So the assignment
is placed in the same unbroken bcm_rx_update_lock section as the content
comparison.
As a side effect, the RTR-request frame feature (which never reach
bcm_send_to_user()) no longer updates rx_stamp/rx_ifindex, since only
the notification path needs them.
Fixes: ffd980f976e7 ("[CAN]: Add broadcast manager (bcm) protocol")
Reported-by: sashiko-bot@kernel.org
Link: https://lore.kernel.org/linux-can/20260707145135.5BC831F00A3A@smtp.kernel.org/
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
net/can/bcm.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/net/can/bcm.c b/net/can/bcm.c
index 9d0193170808..5591a0aed152 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -768,15 +768,10 @@ static void bcm_rx_handler(struct sk_buff *skb, void *data)
}
/* disable timeout */
hrtimer_cancel(&op->timer);
- /* save rx timestamp */
- op->rx_stamp = skb->tstamp;
- /* save originator for recvfrom() */
- op->rx_ifindex = skb->dev->ifindex;
-
/* snapshot RTR content under lock: op->flags/op->frames may be
* updated concurrently by bcm_rx_setup().
*/
spin_lock_bh(&op->bcm_rx_update_lock);
@@ -803,10 +798,18 @@ static void bcm_rx_handler(struct sk_buff *skb, void *data)
traffic_flags |= RX_OWN;
}
spin_lock_bh(&op->bcm_rx_update_lock);
+ /* save rx timestamp and originator for recvfrom() under lock.
+ * For an op subscribed on all interfaces (ifindex == 0)
+ * bcm_rx_handler() can run concurrently on different CPUs so
+ * the CAN content and the meta data must be bundled correctly.
+ */
+ op->rx_stamp = skb->tstamp;
+ op->rx_ifindex = skb->dev->ifindex;
+
if (op->flags & RX_FILTER_ID) {
/* the easiest case */
bcm_rx_update_and_send(op, op->last_frames, rxframe,
traffic_flags);
goto rx_starttimer;
--
2.53.0
^ permalink raw reply related [flat|nested] 29+ messages in thread
* Re: [PATCH v7 06/10] can: bcm: extend bcm_tx_lock usage for data and timer updates
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
(?)
@ 2026-07-08 15:34 ` sashiko-bot
-1 siblings, 0 replies; 29+ messages in thread
From: sashiko-bot @ 2026-07-08 15:34 UTC (permalink / raw)
To: Oliver Hartkopp
Cc: Marc Kleine-Budde, Oliver Hartkopp, linux-can, Oleksij Rempel,
Vincent Mailhol
Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
Pre-existing issues:
- [High] bcm_can_tx() drops bcm_tx_lock between reading the frame and incrementing currframe, leading to frame sequence corruption if reset concurrently.
- [High] Torn reads and race conditions when reading timer variables, count, and flags outside of the protective spinlock in bcm_tx_timeout_handler() and bcm_proc_show().
--
--- Patch [6]: [PATCH v7 06/10] can: bcm: extend bcm_tx_lock usage for data and timer updates ---
commit 71db2892f1d82b77f3491796e67189db751f4bb1
Author: Oliver Hartkopp <socketcan@hartkopp.net>
can: bcm: extend bcm_tx_lock usage for data and timer updates
Stage new CAN frame content for an existing tx op into a kmalloc()'d
buffer and validate it there, mirroring the approach already used in
bcm_rx_setup(). Only copy the validated data into op->frames while
holding op->bcm_tx_lock, so bcm_can_tx() and bcm_tx_timeout_handler()
can no longer observe a partially updated or unvalidated frame.
> diff --git a/net/can/bcm.c b/net/can/bcm.c
> --- a/net/can/bcm.c
> +++ b/net/can/bcm.c
> @@ -477,8 +483,17 @@ static enum hrtimer_restart bcm_tx_timeout_handler(struct hrtimer *hrtimer)
> {
> struct bcm_op *op = container_of(hrtimer, struct bcm_op, timer);
> struct bcm_msg_head msg_head;
> + bool tx_ival1, tx_ival2;
>
> - if (op->kt_ival1 && (op->count > 0)) {
> + /* snapshot kt_ival1/kt_ival2/count under lock to avoid torn
> + * ktime_t reads racing with concurrent bcm_tx_setup() updates
> + */
> + spin_lock_bh(&op->bcm_tx_lock);
> + tx_ival1 = op->kt_ival1 && (op->count > 0);
> + tx_ival2 = !!op->kt_ival2;
> + spin_unlock_bh(&op->bcm_tx_lock);
> +
> + if (tx_ival1) {
> bcm_can_tx(op, NULL);
> if (!op->count && (op->flags & TX_COUNTEVT)) {
[Severity: High]
This is a pre-existing issue, but does bcm_tx_timeout_handler() have torn
reads for timer variables?
Just after the lock is dropped in the hunk above, bcm_tx_timeout_handler()
creates a notification to the user:
bcm_tx_timeout_handler() {
...
spin_unlock_bh(&op->bcm_tx_lock);
if (tx_ival1) {
bcm_can_tx(op, NULL);
if (!op->count && (op->flags & TX_COUNTEVT)) {
...
msg_head.count = op->count;
msg_head.ival1 = op->ival1;
msg_head.ival2 = op->ival2;
...
}
Because ival1 and ival2 are multi-word structures read outside the lock,
could a concurrent bcm_tx_setup() holding bcm_tx_lock overwrite these fields
and tear the values sent to user space?
Also, does bcm_proc_show() have a similar issue since it reads 64-bit
kt_ival1 and kt_ival2 under only rcu_read_lock() on 32-bit platforms?
[ ... ]
> @@ -1028,11 +1045,23 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
[ ... ]
> + spin_lock_bh(&op->bcm_tx_lock);
> +
> + /* update CAN frames content */
> + memcpy(op->frames, new_frames, msg_head->nframes * op->cfsiz);
> +
> op->flags = msg_head->flags;
>
> - /* only lock for unlikely count/nframes/currframe changes */
> if (op->nframes != msg_head->nframes ||
> - op->flags & TX_RESET_MULTI_IDX ||
> - op->flags & SETTIMER) {
> -
> - spin_lock_bh(&op->bcm_tx_lock);
> + op->flags & TX_RESET_MULTI_IDX) {
> + /* potentially update changed nframes */
> + op->nframes = msg_head->nframes;
> + /* restart multiple frame transmission */
> + op->currframe = 0;
> + }
[Severity: High]
This isn't a bug introduced by this patch, but does resetting currframe
here race with bcm_can_tx()?
Looking at bcm_can_tx(), it drops the lock between reading the frame and
incrementing currframe:
bcm_can_tx() {
if (!cf) {
spin_lock_bh(&op->bcm_tx_lock);
memcpy(&cframe, op->frames + op->cfsiz * op->currframe, ...);
spin_unlock_bh(&op->bcm_tx_lock);
}
...
can_send(skb, 1);
...
spin_lock_bh(&op->bcm_tx_lock);
...
op->currframe++;
if (op->currframe >= op->nframes)
op->currframe = 0;
spin_unlock_bh(&op->bcm_tx_lock);
}
If a concurrent bcm_tx_setup() acquires bcm_tx_lock, writes new frames, and
sets op->currframe = 0 while bcm_can_tx() is busy sending the old frame,
bcm_can_tx() will re-acquire the lock and erroneously increment currframe
to 1.
Will this skip the newly programmed first frame and cause sequence
corruption?
--
Sashiko AI review · https://sashiko.dev/#/patchset/20260708-bcm_fixes-v7-0-c78896b342e4@hartkopp.net?part=6
^ permalink raw reply [flat|nested] 29+ messages in thread
* Re: [PATCH v7 04/10] can: bcm: fix CAN frame rx/tx statistics
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
(?)
@ 2026-07-08 15:34 ` sashiko-bot
-1 siblings, 0 replies; 29+ messages in thread
From: sashiko-bot @ 2026-07-08 15:34 UTC (permalink / raw)
To: Oliver Hartkopp
Cc: Oleksij Rempel, linux-can, Marc Kleine-Budde, Vincent Mailhol,
Oliver Hartkopp
Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
New issues:
- [Medium] The statistics reset logic introduces a race condition for RX operations handling RTR frames, directly contradicting the commit's claim of preventing races.
Pre-existing issues:
- [Medium] Concurrent lockless updates to `op->rx_stamp` and `op->rx_ifindex` cause data races and metadata corruption.
--
--- Patch [4]: [PATCH v7 04/10] can: bcm: fix CAN frame rx/tx statistics ---
commit df517d421b8dc860bfb7f92f0c455c27cf5d743e
Author: Oliver Hartkopp <socketcan@hartkopp.net>
can: bcm: fix CAN frame rx/tx statistics
This patch attempts to fix data races in the CAN broadcast manager's receive
and transmit statistics by using atomic operations. It introduces a helper
to update and reset statistics to prevent overflow.
> diff --git a/net/can/bcm.c b/net/can/bcm.c
> index af4bb4182bc29..340b7fc89744e 100644
> --- a/net/can/bcm.c
> +++ b/net/can/bcm.c
[ ... ]
> @@ -290,6 +294,15 @@ static int bcm_proc_show(struct seq_file *m, void *v)
> }
> #endif /* CONFIG_PROC_FS */
>
> +static void bcm_update_stats(struct bcm_op *op)
> +{
> + /* prevent statistics overflow */
> + if (atomic_long_inc_return(&op->frames_abs) > LONG_MAX / 100) {
> + atomic_long_set(&op->frames_filtered, 0);
> + atomic_long_set(&op->frames_abs, 0);
> + }
> +}
> +
[Severity: Medium]
If an application sets up an RX op with RX_RTR_FRAME enabled, and multiple
RTR frames arrive concurrently, could there be a race condition here?
Because bcm_update_stats() is called under bcm_tx_lock in bcm_can_tx() and
under bcm_rx_update_lock in bcm_rx_handler(), both functions can execute
for the same RX op when processing an RTR frame.
If multiple CPUs handle RTR frames concurrently, they might execute
bcm_update_stats() using different locks, causing a race on this reset
logic where valid increments are overwritten or frames_filtered temporarily
exceeds frames_abs.
> /*
> * bcm_can_tx - send the (next) CAN frame to the appropriate CAN interface
> * of the given bcm tx op
> @@ -344,7 +357,7 @@ static void bcm_can_tx(struct bcm_op *op, struct canfd_frame *cf)
> spin_lock_bh(&op->bcm_tx_lock);
>
> if (!err)
> - op->frames_abs++;
> + bcm_update_stats(op);
>
> op->currframe++;
>
[ ... ]
> @@ -748,16 +758,19 @@ static void bcm_rx_handler(struct sk_buff *skb, void *data)
> op->rx_stamp = skb->tstamp;
> /* save originator for recvfrom() */
> op->rx_ifindex = skb->dev->ifindex;
[Severity: Medium]
This isn't a bug introduced by this patch, but does this lockless update of
rx_stamp and rx_ifindex cause data races?
When multiple CAN frames are received simultaneously on different CPUs (e.g.,
listening on all interfaces), these fields are updated outside the protection
of bcm_rx_update_lock.
This can lead to torn reads of the 64-bit timestamp on 32-bit systems, or
metadata mismatches where a CAN frame is sent to userspace with a timestamp
from a different frame.
> - /* update statistics */
> - op->frames_abs++;
>
> - /* snapshot the flag under lock: op->flags/op->frames may be updated
> - * concurrently by bcm_rx_setup().
> + /* snapshot RTR content under lock: op->flags/op->frames may be
> + * updated concurrently by bcm_rx_setup().
> */
> spin_lock_bh(&op->bcm_rx_update_lock);
> +
> + /* update statistics with lock analogue to bcm_rx_changed() callers */
> + bcm_update_stats(op);
> +
> rtr_frame = op->flags & RX_RTR_FRAME;
> if (rtr_frame)
> memcpy(&rtrframe, op->frames, op->cfsiz);
> +
> spin_unlock_bh(&op->bcm_rx_update_lock);
>
> if (rtr_frame) {
--
Sashiko AI review · https://sashiko.dev/#/patchset/20260708-bcm_fixes-v7-0-c78896b342e4@hartkopp.net?part=4
^ permalink raw reply [flat|nested] 29+ messages in thread
* Re: [PATCH v7 05/10] can: bcm: add missing rcu list annotations and operations
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
(?)
@ 2026-07-08 15:35 ` sashiko-bot
-1 siblings, 0 replies; 29+ messages in thread
From: sashiko-bot @ 2026-07-08 15:35 UTC (permalink / raw)
To: Oliver Hartkopp
Cc: Oliver Hartkopp, linux-can, Vincent Mailhol, Marc Kleine-Budde,
Oleksij Rempel
Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
Pre-existing issues:
- [High] Unlocked 64-bit `ktime_t` assignments allow torn reads on 32-bit systems, causing incorrect timer expiries.
--
--- Patch [5]: [PATCH v7 05/10] can: bcm: add missing rcu list annotations and operations ---
commit 356a7e056868b1df56b247c6708d4c5bdd80c8f0
Author: Oliver Hartkopp <socketcan@hartkopp.net>
can: bcm: add missing rcu list annotations and operations
This commit adds missing list_add_rcu() calls in bcm_tx_setup() and
bcm_rx_setup() to ensure bcm_op structures are properly initialized
before being traversed by bcm_proc_show() under rcu_read_lock(). It
also fixes the mirroring removal side in bcm_release() by properly
unlinking operations with list_del_rcu() before freeing them via
bcm_remove_op().
Link: https://lore.kernel.org/linux-can/20260610094654.A1FFE1F00893@smtp.kernel.org/
> diff --git a/net/can/bcm.c b/net/can/bcm.c
> index 340b7fc89744e..fca7c714cc52f 100644
> --- a/net/can/bcm.c
> +++ b/net/can/bcm.c
[ ... ]
> @@ -1163,6 +1163,10 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
> op->flags |= TX_ANNOUNCE;
> }
>
> + /* add this bcm_op to the list of the tx_ops? */
> + if (add_op_to_list)
> + list_add_rcu(&op->list, &bo->tx_ops);
> +
[Severity: High]
This is a pre-existing issue, but while reviewing this setup code I noticed
a potential torn read problem on 32-bit systems.
Earlier in bcm_tx_setup(), the 64-bit ktime_t values are written under
bcm_tx_lock:
spin_lock_bh(&op->bcm_tx_lock);
op->ival1 = msg_head->ival1;
op->ival2 = msg_head->ival2;
op->kt_ival1 = bcm_timeval_to_ktime(msg_head->ival1);
op->kt_ival2 = bcm_timeval_to_ktime(msg_head->ival2);
spin_unlock_bh(&op->bcm_tx_lock);
However, if the hrtimer fires on another CPU concurrently,
bcm_tx_timeout_handler() reads these 64-bit values without acquiring
bcm_tx_lock:
if (op->kt_ival1 && (op->count > 0)) {
bcm_can_tx(op, NULL);
// ...
} else if (op->kt_ival2) {
And bcm_tx_set_expiry() also reads them unlocked to set the timer expiry:
if (op->kt_ival1 && op->count)
ival = op->kt_ival1;
else if (op->kt_ival2)
ival = op->kt_ival2;
Could an unlocked concurrent read of op->kt_ival1 or op->kt_ival2 cause a
torn read on 32-bit systems, resulting in a corrupted or negative timer
expiry?
If this corrupted value is passed to hrtimer_set_expires(), might it schedule
the timer in the past and lead to an immediate expiration and subsequent
softirq storm for repeating cyclic timers?
> if (op->flags & TX_ANNOUNCE)
> bcm_can_tx(op, NULL);
>
--
Sashiko AI review · https://sashiko.dev/#/patchset/20260708-bcm_fixes-v7-0-c78896b342e4@hartkopp.net?part=5
^ permalink raw reply [flat|nested] 29+ messages in thread
* Re: [PATCH v7 01/10] can: bcm: defer rx_op deallocation to workqueue to fix thrtimer UAF
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
(?)
@ 2026-07-08 15:36 ` sashiko-bot
-1 siblings, 0 replies; 29+ messages in thread
From: sashiko-bot @ 2026-07-08 15:36 UTC (permalink / raw)
To: Oliver Hartkopp
Cc: Oleksij Rempel, Vincent Mailhol, linux-can, Oliver Hartkopp,
Marc Kleine-Budde
Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
Pre-existing issues:
- [High] Concurrent lockless access to op->frames and metadata between process context setups (bcm_rx_setup / bcm_tx_setup) and softirq handlers (bcm_rx_handler / bcm_can_tx).
--
--- Patch [1]: [PATCH v7 01/10] can: bcm: defer rx_op deallocation to workqueue to fix thrtimer UAF ---
commit a3f554e14b7943cd3930531fdd91052fab6a02ca
Author: Lee Jones <lee@kernel.org>
can: bcm: defer rx_op deallocation to workqueue to fix thrtimer UAF
This commit resolves a use-after-free issue when tearing down BCM RX
operations by deferring the cancellation of timers and memory deallocation
to a dedicated workqueue. It also takes a reference on the socket to ensure
it is not freed while timers are still armed.
> diff --git a/net/can/bcm.c b/net/can/bcm.c
> index a4bef2c48a559..bdf53241bd7b3 100644
> --- a/net/can/bcm.c
> +++ b/net/can/bcm.c
[ ... ]
> @@ -1060,6 +1081,7 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
>
> /* bcm_can_tx / bcm_tx_timeout_handler needs this */
> op->sk = sk;
> + sock_hold(sk);
[Severity: High]
This is a pre-existing issue, but does bcm_tx_setup() overwrite op->frames
directly from userspace without holding bcm_tx_lock?
When updating an existing operation, bcm_tx_setup() appears to do:
/* update CAN frames content */
for (i = 0; i < msg_head->nframes; i++) {
cf = op->frames + op->cfsiz * i;
err = memcpy_from_msg((u8 *)cf, msg, op->cfsiz);
While concurrently, bcm_can_tx() drops the lock before dereferencing a
pointer into op->frames:
/* read currframe under lock protection */
spin_lock_bh(&op->bcm_tx_lock);
cf = op->frames + op->cfsiz * op->currframe;
spin_unlock_bh(&op->bcm_tx_lock);
...
skb_put_data(skb, cf, op->cfsiz);
Can this allow a concurrent bcm_tx_setup() on another CPU to overwrite the
frames, leading to the transmission of partially updated (torn) CAN frames?
> op->ifindex = ifindex;
>
> /* initialize uninitialized (kzalloc) structure */
[ ... ]
> @@ -1221,6 +1243,7 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
>
> /* bcm_can_tx / bcm_tx_timeout_handler needs this */
> op->sk = sk;
> + sock_hold(sk);
[Severity: High]
This is also a pre-existing issue, but does bcm_rx_setup() modify op->frames
locklessly here as well?
/* update CAN frames content */
err = memcpy_from_msg(op->frames, msg,
msg_head->nframes * op->cfsiz);
This bypasses bcm_rx_update_lock. In bcm_rx_handler(), it attempts to read
safely by taking the lock:
/* snapshot RTR content under lock: op->flags/op->frames may be
* updated concurrently by bcm_rx_setup().
*/
spin_lock_bh(&op->bcm_rx_update_lock);
...
rtr_frame = op->flags & RX_RTR_FRAME;
if (rtr_frame)
memcpy(&rtrframe, op->frames, op->cfsiz);
Because bcm_rx_setup() does not acquire bcm_rx_update_lock when modifying
op->frames directly from userspace, can this result in bcm_rx_handler()
acting on inconsistent metadata or evaluating torn multiplex masks?
> op->ifindex = ifindex;
>
> /* ifindex for timeout events w/o previous frame reception */
--
Sashiko AI review · https://sashiko.dev/#/patchset/20260708-bcm_fixes-v7-0-c78896b342e4@hartkopp.net?part=1
^ permalink raw reply [flat|nested] 29+ messages in thread
* Re: [PATCH v7 02/10] can: bcm: fix lockless bound/ifindex race and silent RX_SETUP failure
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
(?)
@ 2026-07-08 15:36 ` sashiko-bot
-1 siblings, 0 replies; 29+ messages in thread
From: sashiko-bot @ 2026-07-08 15:36 UTC (permalink / raw)
To: Oliver Hartkopp
Cc: Oleksij Rempel, linux-can, Vincent Mailhol, Oliver Hartkopp,
Marc Kleine-Budde
Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider:
Pre-existing issues:
- [High] Missing RCU memory barriers for tx_ops and rx_ops list insertions and iterations, risking unhandled page faults in procfs.
- [High] Unsynchronized updates to active BCM RX operations can corrupt CAN frame filtering.
- [High] Unsynchronized updates to active BCM TX operations can transmit torn CAN frames.
--
--- Patch [2]: [PATCH v7 02/10] can: bcm: fix lockless bound/ifindex race and silent RX_SETUP failure ---
commit a05a784ab0fbce0367eb9df72d3333b7e2033fcb
Author: Oliver Hartkopp <socketcan@hartkopp.net>
can: bcm: fix lockless bound/ifindex race and silent RX_SETUP failure
bcm_sendmsg() reads bo->ifindex and checks bo->bound before taking
lock_sock(), while bcm_notify(), bcm_connect() and bcm_release() all
mutate both fields under that same lock. This commit fixes a race
where bcm_sendmsg() could observe an inconsistent combination of these
fields. It also ensures bcm_rx_setup() reports -ENODEV when the target
device concurrently disappears.
Link: https://lore.kernel.org/linux-can/CAGp+u1aBK8QVjsvAxM2Ldzep4rEbsP9x_pV3At4g=h1kVEtyhA@mail.gmail.com/
> diff --git a/net/can/bcm.c b/net/can/bcm.c
> index bdf53241bd7b3..b612135b017d1 100644
> --- a/net/can/bcm.c
> +++ b/net/can/bcm.c
> @@ -1323,6 +1323,11 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
>
> op->rx_reg_dev = dev;
> dev_put(dev);
> + } else {
> + /* the requested device is gone - do not
> + * silently succeed without registering
> + */
> + err = -ENODEV;
> }
>
> } else
[Severity: High]
This is a pre-existing issue, but can unsynchronized updates to active
BCM RX operations corrupt CAN frame filtering?
When updating an existing BCM RX operation, bcm_rx_setup() in net/can/bcm.c
copies data from user space directly into op->frames via:
err = memcpy_from_msg(op->frames, msg, msg_head->nframes * op->cfsiz);
This happens without disabling softirqs or taking a lock that the softirq
handler respects. Concurrently, bcm_rx_handler() runs in NET_RX_SOFTIRQ
context and accesses these fields locklessly to evaluate incoming CAN
frames or generate RTR replies.
Does this data race allow the softirq to observe torn data, resulting in
corrupted CAN frame filtering or malformed RTR replies?
[Severity: High]
This is a pre-existing issue, but do bcm_rx_setup() and bcm_tx_setup()
need RCU release barriers when inserting into bo->rx_ops and bo->tx_ops?
In net/can/bcm.c, new operations are inserted using list_add() instead
of list_add_rcu():
list_add(&op->list, &bo->tx_ops);
// and
list_add(&op->list, &bo->rx_ops);
Concurrently, bcm_proc_show() iterates through these lists. For rx_ops,
it uses list_for_each_entry_rcu() (but the insertion lacked a release
barrier). For tx_ops, it iterates inside rcu_read_lock() using:
list_for_each_entry(op, &bo->tx_ops, list) {
which lacks an acquire barrier. Since list_add() doesn't execute a write
memory barrier, can concurrent procfs readers observe the newly linked
node before its internal pointers are fully initialized, potentially
dereferencing garbage pointers and causing an unhandled page fault?
[ ... ]
> @@ -1396,12 +1401,13 @@ static int bcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
> {
> struct sock *sk = sock->sk;
> struct bcm_sock *bo = bcm_sk(sk);
> - int ifindex = bo->ifindex; /* default ifindex for this bcm_op */
> + int ifindex;
> struct bcm_msg_head msg_head;
> int cfsiz;
> int ret; /* read bytes or error codes as return value */
>
> - if (!bo->bound)
> + /* Lockless fast-path check for bound socket */
> + if (!READ_ONCE(bo->bound))
> return -ENOTCONN;
>
> /* check for valid message length from userspace */
[Severity: High]
This is a pre-existing issue, but can unsynchronized updates to active
BCM TX operations cause the transmission of torn CAN frames?
When bcm_sendmsg() delegates to bcm_tx_setup() in net/can/bcm.c to update
an existing BCM TX operation, bcm_tx_setup() copies data from user space
into op->frames without acquiring op->bcm_tx_lock:
err = memcpy_from_msg((u8 *)cf, msg, op->cfsiz);
Concurrently, the transmission timer may fire and execute bcm_can_tx().
It calculates the frame pointer under the lock but drops the lock before
copying the frame data locklessly into the SKB:
skb_put_data(skb, cf, op->cfsiz);
Does this data race allow a partially written (torn) CAN frame to be
constructed and transmitted onto the CAN bus, causing data corruption
on the network?
--
Sashiko AI review · https://sashiko.dev/#/patchset/20260708-bcm_fixes-v7-0-c78896b342e4@hartkopp.net?part=2
^ permalink raw reply [flat|nested] 29+ messages in thread
* Re: [PATCH v7 09/10] can: bcm: fix stale rx/tx ops after device removal
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
(?)
@ 2026-07-08 15:40 ` sashiko-bot
-1 siblings, 0 replies; 29+ messages in thread
From: sashiko-bot @ 2026-07-08 15:40 UTC (permalink / raw)
To: Oliver Hartkopp
Cc: Oleksij Rempel, linux-can, Marc Kleine-Budde, Oliver Hartkopp,
Vincent Mailhol
Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [High] Setting `op->ifindex = 0` for `tx_ops` on NETDEV_UNREGISTER orphans the operations, preventing reconfiguration and causing memory leaks.
- [Medium] `bcm_rx_setup()` silently ignores registration failures for existing operations, falsely reporting success to userspace.
--
--- Patch [9]: [PATCH v7 09/10] can: bcm: fix stale rx/tx ops after device removal ---
commit 685050073b3ab1afd17b250b634cb2dfd5941250
Author: Oliver Hartkopp <socketcan@hartkopp.net>
can: bcm: fix stale rx/tx ops after device removal
This commit modifies bcm_rx_setup() to correctly re-register an RX operation
when a concurrent NETDEV_UNREGISTER has torn down its previous registration.
It also updates bcm_notify() to stop the TX timer and clear op->ifindex
for affected tx_ops when a device is unregistered, preventing cyclic frames
from being transmitted to unrelated devices.
Link: https://lore.kernel.org/linux-can/20260708094536.DDF821F00A3A@smtp.kernel.org/
> diff --git a/net/can/bcm.c b/net/can/bcm.c
> index 4bdca72f9327f..9d01931708081 100644
> --- a/net/can/bcm.c
> +++ b/net/can/bcm.c
[ ... ]
> @@ -1473,18 +1485,21 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
> err = -ENODEV;
> }
>
> - } else
> + } else {
> err = can_rx_register(sock_net(sk), NULL, op->can_id,
> REGMASK(op->can_id),
> bcm_rx_handler, op, "bcm", sk);
> - if (err) {
> + }
> +
> + if (err && new_op) {
[Severity: Medium]
Does adding the new_op check here silently swallow registration errors for existing
operations?
If an existing operation (new_op == 0) attempts to re-register after being unregistered,
and dev_get_by_index() or can_rx_register() fails, err will be set (e.g., -ENODEV).
Because of the && new_op condition, the error is ignored and the function will return
success to userspace, despite the comment above indicating "do not silently succeed
without registering".
> /* this bcm rx op is broken -> remove it */
> bcm_remove_op(op);
> return err;
> }
[ ... ]
> @@ -1704,11 +1719,25 @@ static void bcm_notify(struct bcm_sock *bo, unsigned long msg,
> case NETDEV_UNREGISTER:
> lock_sock(sk);
>
> - /* remove device specific receive entries */
> + /* rx_ops: remove device specific receive entries */
> list_for_each_entry(op, &bo->rx_ops, list)
> if (op->rx_reg_dev == dev)
> bcm_rx_unreg(dev, op);
>
> + /* tx_ops: stop device specific cyclic transmissions on the
> + * vanishing ifindex and invalidate the op->ifindex.
> + */
> + list_for_each_entry(op, &bo->tx_ops, list) {
> + if (op->ifindex != dev->ifindex)
> + continue;
> +
> + spin_lock_bh(&op->bcm_tx_lock);
> + op->ifindex = 0;
[Severity: High]
Does setting op->ifindex = 0 permanently orphan the operation and cause a memory leak?
The commit message states the index is cleared "so that a later TX_SETUP update can
reconfigure it". However, bcm_tx_setup() rejects an ifindex of 0 with -ENODEV:
bcm_tx_setup() {
...
if (!ifindex)
return -ENODEV;
...
}
Furthermore, bcm_find_op() strictly requires an exact match on ifindex.
Since userspace can't pass 0, and passing the old valid index will no longer match
the zeroed op->ifindex, any subsequent TX_SETUP will fail to find it and will allocate a
duplicate bcm_op. A TX_DELETE will similarly fail to find and remove the operation,
leaving it as a zombie.
> + spin_unlock_bh(&op->bcm_tx_lock);
> +
> + hrtimer_cancel(&op->timer);
> + }
> +
--
Sashiko AI review · https://sashiko.dev/#/patchset/20260708-bcm_fixes-v7-0-c78896b342e4@hartkopp.net?part=9
^ permalink raw reply [flat|nested] 29+ messages in thread
* Re: [PATCH v7 10/10] can: bcm: fix data race on rx_stamp/rx_ifindex in bcm_rx_handler()
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
(?)
@ 2026-07-08 15:48 ` sashiko-bot
-1 siblings, 0 replies; 29+ messages in thread
From: sashiko-bot @ 2026-07-08 15:48 UTC (permalink / raw)
To: Oliver Hartkopp
Cc: Oliver Hartkopp, Vincent Mailhol, Oleksij Rempel,
Marc Kleine-Budde, linux-can
Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
Pre-existing issues:
- [High] Multiplexed or throttled CAN frames share a single global `rx_stamp` and `rx_ifindex`, which are overwritten by rejected or unrelated multiplex frames, causing metadata corruption when sending throttled frames to userspace.
--
--- Patch [10]: [PATCH v7 10/10] can: bcm: fix data race on rx_stamp/rx_ifindex in bcm_rx_handler() ---
commit 981b0672b1caa15044dae2fc2e2b6c5ccb8394f9
Author: Oliver Hartkopp <socketcan@hartkopp.net>
can: bcm: fix data race on rx_stamp/rx_ifindex in bcm_rx_handler()
This commit moves the updates to op->rx_stamp and op->rx_ifindex inside
the bcm_rx_update_lock section to prevent data races. It also notes that
metadata is bundled correctly when running concurrently on different CPUs
for wildcard interface subscriptions.
Link: https://lore.kernel.org/linux-can/20260707145135.5BC831F00A3A@smtp.kernel.org/
> diff --git a/net/can/bcm.c b/net/can/bcm.c
> --- a/net/can/bcm.c
> +++ b/net/can/bcm.c
[ ... ]
> @@ -805,6 +800,14 @@ static void bcm_rx_handler(struct sk_buff *skb, void *data)
>
> spin_lock_bh(&op->bcm_rx_update_lock);
>
> + /* save rx timestamp and originator for recvfrom() under lock.
> + * For an op subscribed on all interfaces (ifindex == 0)
> + * bcm_rx_handler() can run concurrently on different CPUs so
> + * the CAN content and the meta data must be bundled correctly.
> + */
> + op->rx_stamp = skb->tstamp;
> + op->rx_ifindex = skb->dev->ifindex;
> +
[Severity: High]
This is a pre-existing issue, but by updating op->rx_stamp and
op->rx_ifindex unconditionally here before checking the multiplex mask,
are we risking metadata corruption for throttled frames?
If a valid multiplexed frame is received and throttled, its payload is
buffered. If another frame with the same CAN ID but a non-matching
multiplex ID (or on a different interface) arrives while the throttle
timer is running, we reach this code and overwrite the global op->rx_stamp
and op->rx_ifindex.
When the timer later expires, bcm_rx_thr_flush() flushes all pending
throttled MUX frames using the shared overwritten metadata:
net/can/bcm.c:bcm_rx_thr_flush() {
...
for (i = 1; i < op->nframes; i++)
updated += bcm_rx_do_flush(op, i);
...
}
Which propagates to bcm_rx_changed():
net/can/bcm.c:bcm_rx_changed() {
...
bcm_send_to_user(op, &head, data, 1);
...
}
Could this cause applications to respond on the wrong CAN bus interface if
recvfrom() returns the incorrectly overwritten ifindex?
> if (op->flags & RX_FILTER_ID) {
> /* the easiest case */
> bcm_rx_update_and_send(op, op->last_frames, rxframe,
--
Sashiko AI review · https://sashiko.dev/#/patchset/20260708-bcm_fixes-v7-0-c78896b342e4@hartkopp.net?part=10
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2026-07-08 15:21 [PATCH v7 00/10] can: bcm: collected fixes - final2 :-D Oliver Hartkopp
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
2026-07-08 15:21 ` [PATCH v7 01/10] can: bcm: defer rx_op deallocation to workqueue to fix thrtimer UAF Oliver Hartkopp
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
2026-07-08 15:36 ` sashiko-bot
2026-07-08 15:21 ` [PATCH v7 02/10] can: bcm: fix lockless bound/ifindex race and silent RX_SETUP failure Oliver Hartkopp
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
2026-07-08 15:36 ` sashiko-bot
2026-07-08 15:21 ` [PATCH v7 03/10] can: bcm: add locking when updating filter and timer values Oliver Hartkopp
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
2026-07-08 15:21 ` [PATCH v7 04/10] can: bcm: fix CAN frame rx/tx statistics Oliver Hartkopp
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
2026-07-08 15:34 ` sashiko-bot
2026-07-08 15:21 ` [PATCH v7 05/10] can: bcm: add missing rcu list annotations and operations Oliver Hartkopp
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
2026-07-08 15:35 ` sashiko-bot
2026-07-08 15:21 ` [PATCH v7 06/10] can: bcm: extend bcm_tx_lock usage for data and timer updates Oliver Hartkopp
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
2026-07-08 15:34 ` sashiko-bot
2026-07-08 15:21 ` [PATCH v7 07/10] can: bcm: validate frame length in bcm_rx_setup() for RTR replies Oliver Hartkopp
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
2026-07-08 15:21 ` [PATCH v7 08/10] can: bcm: add missing device refcount for CAN filter removal Oliver Hartkopp
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
2026-07-08 15:21 ` [PATCH v7 09/10] can: bcm: fix stale rx/tx ops after device removal Oliver Hartkopp
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
2026-07-08 15:40 ` sashiko-bot
2026-07-08 15:21 ` [PATCH v7 10/10] can: bcm: fix data race on rx_stamp/rx_ifindex in bcm_rx_handler() Oliver Hartkopp
2026-07-08 15:21 ` Oliver Hartkopp via B4 Relay
2026-07-08 15:48 ` sashiko-bot
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