* [PATCH v5 1/3] can: remove CAN filters independent from namespace
2026-09-29 16:34 [PATCH v5 0/3] CAN netlayer fixes for stable Oliver Hartkopp
@ 2026-09-29 16:34 ` Oliver Hartkopp
2026-10-03 5:48 ` netdev-bot+sashiko
2026-09-29 16:34 ` [PATCH v5 2/3] can: convert unreliable ARPHRD_CAN type checks to robust can_get_ml_priv() Oliver Hartkopp
2026-09-29 16:34 ` [PATCH v5 3/3] can: fix unique skb identifier regression under RPS Oliver Hartkopp
2 siblings, 1 reply; 7+ messages in thread
From: Oliver Hartkopp @ 2026-09-29 16:34 UTC (permalink / raw)
To: linux-can; +Cc: Oliver Hartkopp, Norbert Szetei, stable
When the devices namespace is changed the socket namespace and the device
namespace might differ. The net_eq(dev_net(dev), sock_net(sk)) check in
the CAN protocols netdev notifiers therefore led to skipping the required
removal of the CAN filters from the (namespace changed) CAN devices.
This patch removes the namespace equality check in the netdev notifiers for
BCM, ISOTP and RAW sockets. Since the struct net_device pointer is globally
unique, the notifier should always process the unregister event and remove
the CAN filters if it matches the original socket's bound device pointer.
In bcm.c netdevice comparisons were performed by checking the interface
index (bo->ifindex and op->ifindex) which is not namespace-safe either.
Introduce tracked netdevice pointers (bo->dev and op->tx_dev) for these
referenced devices to enable namespace-save device comparisons.
Additional put all bo->dev accesses in bcm_notify() under lock_sock().
In isotp.c the two missing can_rx_unregister() calling sites are converted
to use dev_net(dev) instead of sock_net(sk) to get the correct namespace.
Fixes: 8e8cda6d737d ("can: initial support for network namespaces")
Reported-by: Norbert Szetei <norbert@doyensec.com>
Link: https://lore.kernel.org/linux-can/CEA6A38A-2646-4ADA-95B4-CBAE2F301A8E@doyensec.com/
Cc: stable@vger.kernel.org
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
net/can/bcm.c | 100 ++++++++++++++++++++++++++++++++++++------------
net/can/isotp.c | 7 +---
net/can/raw.c | 3 --
3 files changed, 78 insertions(+), 32 deletions(-)
diff --git a/net/can/bcm.c b/net/can/bcm.c
index 3d637a1e0ac1..cd3522ec32c0 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -128,18 +128,22 @@ struct bcm_op {
struct canfd_frame sframe;
struct canfd_frame last_sframe;
struct sock *sk;
struct net_device *rx_reg_dev;
netdevice_tracker rx_reg_dev_tracker;
+ struct net_device *tx_dev;
+ netdevice_tracker tx_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 {
struct sock sk;
int bound;
int ifindex;
+ struct net_device *dev;
+ netdevice_tracker dev_tracker;
struct list_head notifier;
struct list_head rx_ops;
struct list_head tx_ops;
unsigned long dropped_usr_msgs;
struct proc_dir_entry *bcm_proc_read;
@@ -933,10 +937,13 @@ static void bcm_free_op_work(struct work_struct *work)
kfree(op->frames);
if ((op->last_frames) && (op->last_frames != &op->last_sframe))
kfree(op->last_frames);
+ if (op->tx_dev)
+ netdev_put(op->tx_dev, &op->tx_dev_tracker);
+
/* 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);
@@ -1072,10 +1079,11 @@ 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;
+ struct net_device *tx_dev;
bool add_op_to_list = false;
unsigned int i;
int err;
/* we need a real device to send frames */
@@ -1103,10 +1111,26 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
* therefore (complexity / locking) it is not supported.
*/
if (msg_head->nframes > op->nframes)
return -E2BIG;
+ /* Re-resolve and re-hold the target device if a concurrent
+ * NETDEV_UNREGISTER already cleared it (see bcm_notify()).
+ * op->ifindex and sock_net(sk) is unchanged.
+ */
+ if (!op->tx_dev) {
+ tx_dev = dev_get_by_index(sock_net(sk), ifindex);
+ if (tx_dev) {
+ op->tx_dev = tx_dev;
+ netdev_hold(tx_dev, &op->tx_dev_tracker,
+ GFP_KERNEL);
+ dev_put(tx_dev);
+ } else {
+ return -ENODEV;
+ }
+ }
+
/* 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
*/
@@ -1169,10 +1193,22 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
op = kzalloc(OPSIZ, GFP_KERNEL);
if (!op)
return -ENOMEM;
+ tx_dev = dev_get_by_index(sock_net(sk), ifindex);
+ if (tx_dev) {
+ op->tx_dev = tx_dev;
+ netdev_hold(tx_dev, &op->tx_dev_tracker, GFP_KERNEL);
+ dev_put(tx_dev);
+ } else {
+ /* prepare op->frames for goto free_op */
+ op->frames = &op->sframe;
+ err = -ENODEV;
+ goto free_op;
+ }
+
spin_lock_init(&op->bcm_tx_lock);
op->can_id = msg_head->can_id;
op->cfsiz = CFSIZ(msg_head->flags);
op->flags = msg_head->flags;
op->nframes = msg_head->nframes;
@@ -1184,12 +1220,14 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
if (msg_head->nframes > 1) {
op->frames = kmalloc_array(msg_head->nframes,
op->cfsiz,
GFP_KERNEL);
if (!op->frames) {
- kfree(op);
- return -ENOMEM;
+ /* prepare op->frames for goto free_op */
+ op->frames = &op->sframe;
+ err = -ENOMEM;
+ goto free_op;
}
} else
op->frames = &op->sframe;
for (i = 0; i < msg_head->nframes; i++) {
@@ -1267,10 +1305,13 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
bcm_tx_start_timer(op);
return msg_head->nframes * op->cfsiz + MHSIZ;
free_op:
+ if (op->tx_dev)
+ netdev_put(op->tx_dev, &op->tx_dev_tracker);
+
if (op->frames != &op->sframe)
kfree(op->frames);
kfree(op);
return err;
}
@@ -1790,46 +1831,47 @@ static int bcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
static void bcm_notify(struct bcm_sock *bo, unsigned long msg,
struct net_device *dev)
{
struct sock *sk = &bo->sk;
struct bcm_op *op;
- int notify_enodev = 0;
+ int sk_err = 0;
- if (!net_eq(dev_net(dev), sock_net(sk)))
- return;
+ lock_sock(sk);
switch (msg) {
case NETDEV_UNREGISTER:
- lock_sock(sk);
/* 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);
/* release an ANYDEV op's claim (see bcm_rx_handler())
* on this now confirmed-gone interface.
*/
- if (!op->ifindex) {
+ if (!op->ifindex && net_eq(dev_net(dev), sock_net(sk))) {
spin_lock_bh(&op->bcm_rx_update_lock);
if (op->if_detected == dev->ifindex)
op->if_detected = 0;
spin_unlock_bh(&op->bcm_rx_update_lock);
}
}
/* tx_ops: stop device specific cyclic transmissions on the
- * vanishing ifindex. Cancelling the timer is enough to stop
+ * vanishing device. Cancelling the timer is enough to stop
* cyclic bcm_can_tx() calls as there is no re-arming.
*/
list_for_each_entry(op, &bo->tx_ops, list)
- if (op->ifindex == dev->ifindex)
+ if (op->tx_dev == dev) {
hrtimer_cancel(&op->timer);
+ netdev_put(op->tx_dev, &op->tx_dev_tracker);
+ op->tx_dev = NULL;
+ }
/* remove device reference, if this is our bound device */
- if (bo->bound && bo->ifindex == dev->ifindex) {
+ if (bo->bound && bo->dev == dev) {
#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);
bo->bcm_proc_read = NULL;
}
@@ -1839,28 +1881,27 @@ static void bcm_notify(struct bcm_sock *bo, unsigned long msg,
* accessed under lock_sock() so it needs no
* annotation.
*/
WRITE_ONCE(bo->bound, 0);
bo->ifindex = 0;
- notify_enodev = 1;
- }
-
- release_sock(sk);
-
- if (notify_enodev) {
- sk->sk_err = ENODEV;
- if (!sock_flag(sk, SOCK_DEAD))
- sk_error_report(sk);
+ netdev_put(bo->dev, &bo->dev_tracker);
+ bo->dev = NULL;
+ sk_err = ENODEV;
}
break;
case NETDEV_DOWN:
- if (bo->bound && bo->ifindex == dev->ifindex) {
- sk->sk_err = ENETDOWN;
- if (!sock_flag(sk, SOCK_DEAD))
- sk_error_report(sk);
- }
+ if (bo->bound && bo->dev == dev)
+ sk_err = ENETDOWN;
+ }
+
+ release_sock(sk);
+
+ if (sk_err) {
+ sk->sk_err = sk_err;
+ if (!sock_flag(sk, SOCK_DEAD))
+ sk_error_report(sk);
}
}
static int bcm_notifier(struct notifier_block *nb, unsigned long msg,
void *ptr)
@@ -1982,10 +2023,14 @@ static int bcm_release(struct socket *sock)
/* remove device reference */
if (bo->bound) {
WRITE_ONCE(bo->bound, 0);
bo->ifindex = 0;
+ if (bo->dev) {
+ netdev_put(bo->dev, &bo->dev_tracker);
+ bo->dev = NULL;
+ }
}
sock_orphan(sk);
sock->sk = NULL;
@@ -2029,25 +2074,32 @@ static int bcm_connect(struct socket *sock, struct sockaddr_unsized *uaddr, int
ret = -ENODEV;
goto fail;
}
bo->ifindex = dev->ifindex;
+ bo->dev = dev;
+ netdev_hold(dev, &bo->dev_tracker, GFP_KERNEL);
dev_put(dev);
} else {
/* no interface reference for ifindex = 0 ('any' CAN device) */
bo->ifindex = 0;
+ bo->dev = NULL;
}
#if IS_ENABLED(CONFIG_PROC_FS)
if (net->can.bcmproc_dir) {
/* unique socket address as filename */
sprintf(bo->procname, "%llu", sock_i_ino(sk));
bo->bcm_proc_read = proc_create_net_single(bo->procname, 0644,
net->can.bcmproc_dir,
bcm_proc_show, sk);
if (!bo->bcm_proc_read) {
+ if (bo->dev) {
+ netdev_put(bo->dev, &bo->dev_tracker);
+ bo->dev = NULL;
+ }
ret = -ENOMEM;
goto fail;
}
}
#endif /* CONFIG_PROC_FS */
diff --git a/net/can/isotp.c b/net/can/isotp.c
index 155530aedce2..0835a4758a72 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -1490,15 +1490,15 @@ static int isotp_release(struct socket *sock)
/* remove current filters & unregister
* tracked reference so->dev is taken at bind() time with rtnl_lock
*/
if (so->bound && so->dev) {
if (isotp_register_rxid(so))
- can_rx_unregister(net, so->dev, so->rxid,
+ can_rx_unregister(dev_net(so->dev), so->dev, so->rxid,
SINGLE_MASK(so->rxid),
isotp_rcv, sk);
- can_rx_unregister(net, so->dev, so->txid,
+ can_rx_unregister(dev_net(so->dev), so->dev, so->txid,
SINGLE_MASK(so->txid),
isotp_rcv_echo, sk);
netdev_put(so->dev, &so->dev_tracker);
}
@@ -1846,13 +1846,10 @@ static int isotp_getsockopt(struct socket *sock, int level, int optname,
static void isotp_notify(struct isotp_sock *so, unsigned long msg,
struct net_device *dev)
{
struct sock *sk = &so->sk;
- if (!net_eq(dev_net(dev), sock_net(sk)))
- return;
-
if (so->dev != dev)
return;
switch (msg) {
case NETDEV_UNREGISTER:
diff --git a/net/can/raw.c b/net/can/raw.c
index 82d9c0499c95..c5596fc9aac5 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -300,13 +300,10 @@ static int raw_enable_allfilters(struct net *net, struct net_device *dev,
static void raw_notify(struct raw_sock *ro, unsigned long msg,
struct net_device *dev)
{
struct sock *sk = &ro->sk;
- if (!net_eq(dev_net(dev), sock_net(sk)))
- return;
-
if (ro->dev != dev)
return;
switch (msg) {
case NETDEV_UNREGISTER:
--
2.53.0
^ permalink raw reply related [flat|nested] 7+ messages in thread* Re: [PATCH v5 1/3] can: remove CAN filters independent from namespace
2026-09-29 16:34 ` [PATCH v5 1/3] can: remove CAN filters independent from namespace Oliver Hartkopp
@ 2026-10-03 5:48 ` netdev-bot+sashiko
0 siblings, 0 replies; 7+ messages in thread
From: netdev-bot+sashiko @ 2026-10-03 5:48 UTC (permalink / raw)
To: socketcan; +Cc: linux-can, stable, o.rempel, kuba
Thank you for your contribution! Sashiko AI review found 3 potential
issue(s) to consider.
Critical: 0 · High: 1 · Medium: 2 · Low: 0
If you believe none of the issues are legitimate, please reply to each
issue of Medium severity or higher and explain why the AI is wrong.
If any of them are legitimate and you plan to respin, please let patchwork
know by including "pw-bot: cr" as a separate line at the end of your reply
(one such reply per series is enough).
- [High] bcm_release() (net/can/bcm.c) unregisters device-bound receive
filters without holding RTNL, so a concurrent namespace move can still…
- [Medium] The commit message describes a failure that does not occur in
the notifier code.
- [Medium] The patch removes the early net_eq() return in bcm_notify()
and moves lock_sock(sk) above the switch (net/can/bcm.c:1838).
--
can: remove CAN filters independent from namespace
This commit removes the net_eq() namespace check from the BCM, ISOTP and
RAW netdev notifiers, so CAN filters are removed on NETDEV_UNREGISTER
even when the device namespace differs from the socket namespace. In
bcm.c it adds tracked net_device pointers (bo->dev, op->tx_dev) for
device comparisons, and bcm_notify() now takes lock_sock() for every
event. In isotp_release() the can_rx_unregister() calls now use
dev_net(so->dev).
Link: https://lore.kernel.org/linux-can/CEA6A38A-2646-4ADA-95B4-CBAE2F301A8E@doyensec.com/
> When the devices namespace is changed the socket namespace and the device
> namespace might differ. The net_eq(dev_net(dev), sock_net(sk)) check in
> the CAN protocols netdev notifiers therefore led to skipping the required
> removal of the CAN filters from the (namespace changed) CAN devices.
[Severity: Medium]
Is this root cause accurate? In __dev_change_net_namespace(), the
UNREGISTER notifiers run while dev_net(dev) still points to the old
namespace:
net/core/dev.c:__dev_change_net_namespace() {
...
unlist_netdevice(dev);
...
call_netdevice_notifiers(NETDEV_UNREGISTER, dev);
...
netdev_lock(dev);
dev_net_set(dev, net);
netdev_unlock(dev);
dev->ifindex = new_ifindex;
...
}
The bind and registration paths are raw_bind(), isotp_bind(),
bcm_connect(), bcm_rx_setup() and bcm_sendmsg(). All of them look up
the device with dev_get_by_index(sock_net(sk), ...). can_rx_register()
also refuses a device from another namespace:
if (dev && !net_eq(net, dev_net(dev)))
return -ENODEV;
For a socket with filters on the moved device, wouldn't the removed
net_eq() check in raw_notify(), isotp_notify() and bcm_notify() have
passed during the move?
No registration seems able to get in between either:
- raw and isotp register under rtnl.
- bcm_rx_setup() runs under lock_sock(), which bcm_notify() also takes
for UNREGISTER.
- Lookups fail after unlist_netdevice().
I couldn't find a path where the notifier sees a bound device in a
foreign namespace.
The real bug this patch fixes looks like it is in isotp_release():
1. The socket is unlinked from the notifier list.
2. A namespace move completes.
3. can_rx_unregister(sock_net(sk), so->dev, ...) returns early on its
own net_eq() check.
That is a race between release and the move, not the notifier check.
Could the commit message describe the path that was actually hit, or
the reproducer from the report? The BCM rework, which is tagged for
stable, is justified by this description.
> diff --git a/net/can/bcm.c b/net/can/bcm.c
> index 3d637a1e0ac1a..cd3522ec32c0a 100644
> --- a/net/can/bcm.c
> +++ b/net/can/bcm.c
[ ... ]
> @@ -1792,15 +1833,13 @@ static void bcm_notify(struct bcm_sock *bo, unsigned long msg,
> {
> struct sock *sk = &bo->sk;
> struct bcm_op *op;
> - int notify_enodev = 0;
> + int sk_err = 0;
>
> - if (!net_eq(dev_net(dev), sock_net(sk)))
> - return;
> + lock_sock(sk);
[Severity: Medium]
With the early return gone and lock_sock() moved above the switch,
bcm_notifier() now takes the lock of every BCM socket in every
namespace. It does this for every NETDEV_DOWN and NETDEV_UNREGISTER of
any CAN device, while holding RTNL:
net/can/bcm.c:bcm_notifier() {
...
list_for_each_entry(bcm_busy_notifier, &bcm_notifier_list, notifier) {
spin_unlock(&bcm_notifier_lock);
bcm_notify(bcm_busy_notifier, msg, dev);
spin_lock(&bcm_notifier_lock);
}
...
}
Before this change, sockets in other namespaces returned immediately,
and NETDEV_DOWN never took lock_sock().
bcm_sendmsg() holds lock_sock() across bcm_tx_setup(), bcm_rx_setup()
and bcm_tx_send(), and these call memcpy_from_msg() on the user buffer.
Suppose that buffer is on a FUSE-backed mmap that never answers the
read. An unprivileged user in a user namespace can set this up. The
copy then blocks with the socket lock held.
Can a CAN device event in an unrelated namespace then block in
lock_sock() inside bcm_notify() with RTNL held? An example is "ip link
set can0 down" in init_net. That would stall network configuration
system-wide.
A similar stall was already possible for same-namespace UNREGISTER
events. This change extends it to cross-namespace events and to
NETDEV_DOWN. Later patches in this series don't appear to change this.
NETDEV_DOWN only needs the bo->dev == dev comparison, which
raw_notify() and isotp_notify() already do without the socket lock.
Would a lockless check, before lock_sock(), of whether this socket
references dev at all avoid this?
>
> switch (msg) {
[ ... ]
> @@ -1984,6 +2025,10 @@ static int bcm_release(struct socket *sock)
> if (bo->bound) {
> WRITE_ONCE(bo->bound, 0);
> bo->ifindex = 0;
> + if (bo->dev) {
> + netdev_put(bo->dev, &bo->dev_tracker);
> + bo->dev = NULL;
> + }
> }
>
> sock_orphan(sk);
[Severity: High]
Does bcm_release() still have the same window between release and a
namespace move that this patch closes for isotp?
bcm_release() removes the socket from bcm_notifier_list and then takes
only lock_sock(). Unlike raw_release() and isotp_release(), it does not
take rtnl_lock():
net/can/bcm.c:bcm_release() {
...
list_del(&bo->notifier);
spin_unlock(&bcm_notifier_lock);
lock_sock(sk);
...
if (op->rx_reg_dev)
bcm_rx_unreg(op->rx_reg_dev, op);
...
}
The list_del() can happen before a concurrent move's UNREGISTER walk
reaches this socket. In that case bcm_notify() never runs for it, and
op->rx_reg_dev stays set.
bcm_rx_unreg() then reads dev_net(dev) without RTNL, and
can_rx_unregister() reads it a second time:
net/can/bcm.c:bcm_rx_unreg() {
if (op->rx_reg_dev == dev) {
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);
...
}
net/can/af_can.c:can_rx_unregister() {
...
if (dev && !net_eq(net, dev_net(dev)))
return;
...
}
The concurrent writer is dev_net_set() in __dev_change_net_namespace(),
which runs under RTNL and netdev_lock().
Say the argument is sampled as the old namespace and dev_net_set() runs
before the net_eq() check. can_rx_unregister() then returns without
unlinking anything. bcm_rx_unreg() still clears op->rx_reg_dev, and
bcm_remove_op() later frees op.
Can the next frame received on the device in the new namespace then
call bcm_rx_handler() with the freed op?
Now say the check passes instead. hlist_del_rcu() runs under the old
namespace's rcvlists_lock, while code in the new namespace may modify
the same per-device list under its own lock.
Could this corrupt the receive list?
The isotp_release() change to dev_net(so->dev) in this patch relies on
rtnl_lock() being held there. This window existed before this patch,
and later patches in this series don't appear to change bcm_release().
For the BCM part of this fix to be complete, does bcm_release() need
rtnl_lock() around the unregister step, as raw_release() and
isotp_release() take?
--
Sashiko AI review · https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260929163424.16382-1-socketcan%40hartkopp.net
^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH v5 2/3] can: convert unreliable ARPHRD_CAN type checks to robust can_get_ml_priv()
2026-09-29 16:34 [PATCH v5 0/3] CAN netlayer fixes for stable Oliver Hartkopp
2026-09-29 16:34 ` [PATCH v5 1/3] can: remove CAN filters independent from namespace Oliver Hartkopp
@ 2026-09-29 16:34 ` Oliver Hartkopp
2026-10-03 5:48 ` netdev-bot+sashiko
2026-09-29 16:34 ` [PATCH v5 3/3] can: fix unique skb identifier regression under RPS Oliver Hartkopp
2 siblings, 1 reply; 7+ messages in thread
From: Oliver Hartkopp @ 2026-09-29 16:34 UTC (permalink / raw)
To: linux-can; +Cc: Oliver Hartkopp, stable, Oleksij Rempel
Commit 4e096a18867a ("net: introduce CAN specific pointer in the struct
net_device") introduced an explicit way to assign the midlayer private
pointer (dev->ml_priv) to named users like ML_PRIV_CAN.
With this extension the CAN device specific ml_priv assignment became a
robust indicator to identify a valid CAN device, when can_get_ml_priv()
returns a valid pointer.
This has been used directly by the referenced commit in the CAN specific
j1939 and proc code but not in the other parts of the CAN subsystem.
With the TUN/TAP driver a device's ARPHRD type can be controlled by
userspace independently of its midlayer private data (ml_priv). The
TUNSETLINK ioctl allows a down TUN/TAP device to overwrite its hardware
type to become ARPHRD_CAN while dev->ml_priv remains NULL (uninitialized).
Instead of checking dev->type being the unreliable ARPHRD_CAN value convert
the missing "valid CAN devices" checks to can_get_ml_priv().
Fixes: 4e096a18867a ("net: introduce CAN specific pointer in the struct net_device")
Cc: stable@kernel.org
Cc: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
net/can/af_can.c | 12 ++++++------
net/can/bcm.c | 7 ++++---
net/can/gw.c | 7 ++++---
net/can/isotp.c | 5 +++--
net/can/raw.c | 4 ++--
5 files changed, 19 insertions(+), 16 deletions(-)
diff --git a/net/can/af_can.c b/net/can/af_can.c
index 7bc86b176b4d..ef435f22ac93 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -224,11 +224,11 @@ int can_send(struct sk_buff *skb, int loop)
if (unlikely(skb->len > READ_ONCE(skb->dev->mtu))) {
err = -EMSGSIZE;
goto inval_skb;
}
- if (unlikely(skb->dev->type != ARPHRD_CAN)) {
+ if (unlikely(!can_get_ml_priv(skb->dev))) {
err = -EPERM;
goto inval_skb;
}
if (unlikely(!(skb->dev->flags & IFF_UP))) {
@@ -450,11 +450,11 @@ int can_rx_register(struct net *net, struct net_device *dev, canid_t can_id,
struct can_dev_rcv_lists *dev_rcv_lists;
struct can_rcv_lists_stats *rcv_lists_stats = net->can.rcv_lists_stats;
/* insert new receiver (dev,canid,mask) -> (func,data) */
- if (dev && (dev->type != ARPHRD_CAN || !can_get_ml_priv(dev)))
+ if (dev && !can_get_ml_priv(dev))
return -ENODEV;
if (dev && !net_eq(net, dev_net(dev)))
return -ENODEV;
@@ -517,11 +517,11 @@ void can_rx_unregister(struct net *net, struct net_device *dev, canid_t can_id,
struct receiver *rcv = NULL;
struct hlist_head *rcv_list;
struct can_rcv_lists_stats *rcv_lists_stats = net->can.rcv_lists_stats;
struct can_dev_rcv_lists *dev_rcv_lists;
- if (dev && dev->type != ARPHRD_CAN)
+ if (dev && !can_get_ml_priv(dev))
return;
if (dev && !net_eq(net, dev_net(dev)))
return;
@@ -685,11 +685,11 @@ static void can_receive(struct sk_buff *skb, struct net_device *dev)
}
static int can_rcv(struct sk_buff *skb, struct net_device *dev,
struct packet_type *pt, struct net_device *orig_dev)
{
- if (unlikely(dev->type != ARPHRD_CAN || !can_get_ml_priv(dev) ||
+ if (unlikely(!can_get_ml_priv(dev) ||
!can_skb_ext_find(skb) || !can_is_can_skb(skb))) {
pr_warn_once("PF_CAN: dropped non conform CAN skbuff: dev type %d, len %d\n",
dev->type, skb->len);
kfree_skb_reason(skb, SKB_DROP_REASON_CAN_RX_INVALID_FRAME);
@@ -701,11 +701,11 @@ static int can_rcv(struct sk_buff *skb, struct net_device *dev,
}
static int canfd_rcv(struct sk_buff *skb, struct net_device *dev,
struct packet_type *pt, struct net_device *orig_dev)
{
- if (unlikely(dev->type != ARPHRD_CAN || !can_get_ml_priv(dev) ||
+ if (unlikely(!can_get_ml_priv(dev) ||
!can_skb_ext_find(skb) || !can_is_canfd_skb(skb))) {
pr_warn_once("PF_CAN: dropped non conform CAN FD skbuff: dev type %d, len %d\n",
dev->type, skb->len);
kfree_skb_reason(skb, SKB_DROP_REASON_CANFD_RX_INVALID_FRAME);
@@ -717,11 +717,11 @@ static int canfd_rcv(struct sk_buff *skb, struct net_device *dev,
}
static int canxl_rcv(struct sk_buff *skb, struct net_device *dev,
struct packet_type *pt, struct net_device *orig_dev)
{
- if (unlikely(dev->type != ARPHRD_CAN || !can_get_ml_priv(dev) ||
+ if (unlikely(!can_get_ml_priv(dev) ||
!can_skb_ext_find(skb) || !can_is_canxl_skb(skb))) {
pr_warn_once("PF_CAN: dropped non conform CAN XL skbuff: dev type %d, len %d\n",
dev->type, skb->len);
kfree_skb_reason(skb, SKB_DROP_REASON_CANXL_RX_INVALID_FRAME);
diff --git a/net/can/bcm.c b/net/can/bcm.c
index cd3522ec32c0..940b917e3830 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -52,10 +52,11 @@
#include <linux/netdevice.h>
#include <linux/socket.h>
#include <linux/if_arp.h>
#include <linux/skbuff.h>
#include <linux/can.h>
+#include <linux/can/can-ml.h>
#include <linux/can/core.h>
#include <linux/can/skb.h>
#include <linux/can/bcm.h>
#include <linux/slab.h>
#include <linux/workqueue.h>
@@ -1758,11 +1759,11 @@ static int bcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
if (!dev) {
ret = -ENODEV;
goto out_release;
}
- if (dev->type != ARPHRD_CAN) {
+ if (!can_get_ml_priv(dev)) {
dev_put(dev);
ret = -ENODEV;
goto out_release;
}
@@ -1906,11 +1907,11 @@ static void bcm_notify(struct bcm_sock *bo, unsigned long msg,
static int bcm_notifier(struct notifier_block *nb, unsigned long msg,
void *ptr)
{
struct net_device *dev = netdev_notifier_info_to_dev(ptr);
- if (dev->type != ARPHRD_CAN)
+ if (!can_get_ml_priv(dev))
return NOTIFY_DONE;
if (msg != NETDEV_UNREGISTER && msg != NETDEV_DOWN)
return NOTIFY_DONE;
if (unlikely(bcm_busy_notifier)) /* Check for reentrant bug. */
return NOTIFY_DONE;
@@ -2067,11 +2068,11 @@ static int bcm_connect(struct socket *sock, struct sockaddr_unsized *uaddr, int
dev = dev_get_by_index(net, addr->can_ifindex);
if (!dev) {
ret = -ENODEV;
goto fail;
}
- if (dev->type != ARPHRD_CAN) {
+ if (!can_get_ml_priv(dev)) {
dev_put(dev);
ret = -ENODEV;
goto fail;
}
diff --git a/net/can/gw.c b/net/can/gw.c
index 0ec99f68aa45..d9912dea738b 100644
--- a/net/can/gw.c
+++ b/net/can/gw.c
@@ -50,10 +50,11 @@
#include <linux/net.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/skbuff.h>
#include <linux/can.h>
+#include <linux/can/can-ml.h>
#include <linux/can/core.h>
#include <linux/can/skb.h>
#include <linux/can/gw.h>
#include <net/can.h>
#include <net/rtnetlink.h>
@@ -607,11 +608,11 @@ static int cgw_notifier(struct notifier_block *nb,
unsigned long msg, void *ptr)
{
struct net_device *dev = netdev_notifier_info_to_dev(ptr);
struct net *net = dev_net(dev);
- if (dev->type != ARPHRD_CAN)
+ if (!can_get_ml_priv(dev))
return NOTIFY_DONE;
if (msg == NETDEV_UNREGISTER) {
struct cgw_job *gwj = NULL;
struct hlist_node *nx;
@@ -1158,19 +1159,19 @@ static int cgw_create_job(struct sk_buff *skb, struct nlmsghdr *nlh,
gwj->src.dev = __dev_get_by_index(net, gwj->ccgw.src_idx);
if (!gwj->src.dev)
goto out;
- if (gwj->src.dev->type != ARPHRD_CAN)
+ if (!can_get_ml_priv(gwj->src.dev))
goto out;
gwj->dst.dev = __dev_get_by_index(net, gwj->ccgw.dst_idx);
if (!gwj->dst.dev)
goto out;
- if (gwj->dst.dev->type != ARPHRD_CAN)
+ if (!can_get_ml_priv(gwj->dst.dev))
goto out;
/* is sending the skb back to the incoming interface intended? */
if (gwj->src.dev == gwj->dst.dev &&
!(gwj->flags & CGW_FLAGS_CAN_IIF_TX_OK)) {
diff --git a/net/can/isotp.c b/net/can/isotp.c
index 0835a4758a72..d3f79efc9c1e 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -63,10 +63,11 @@
#include <linux/netdevice.h>
#include <linux/socket.h>
#include <linux/if_arp.h>
#include <linux/skbuff.h>
#include <linux/can.h>
+#include <linux/can/can-ml.h>
#include <linux/can/core.h>
#include <linux/can/skb.h>
#include <linux/can/isotp.h>
#include <linux/slab.h>
#include <net/can.h>
@@ -1604,11 +1605,11 @@ static int isotp_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int l
dev = dev_get_by_index(net, addr->can_ifindex);
if (!dev) {
err = -ENODEV;
goto out;
}
- if (dev->type != ARPHRD_CAN) {
+ if (!can_get_ml_priv(dev)) {
err = -ENODEV;
goto out_put_dev;
}
if (READ_ONCE(dev->mtu) < so->ll.mtu) {
err = -EINVAL;
@@ -1888,11 +1889,11 @@ static void isotp_notify(struct isotp_sock *so, unsigned long msg,
static int isotp_notifier(struct notifier_block *nb, unsigned long msg,
void *ptr)
{
struct net_device *dev = netdev_notifier_info_to_dev(ptr);
- if (dev->type != ARPHRD_CAN)
+ if (!can_get_ml_priv(dev))
return NOTIFY_DONE;
if (msg != NETDEV_UNREGISTER && msg != NETDEV_DOWN)
return NOTIFY_DONE;
if (unlikely(isotp_busy_notifier)) /* Check for reentrant bug. */
return NOTIFY_DONE;
diff --git a/net/can/raw.c b/net/can/raw.c
index c5596fc9aac5..7c48ff36e6cd 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -339,11 +339,11 @@ static void raw_notify(struct raw_sock *ro, unsigned long msg,
static int raw_notifier(struct notifier_block *nb, unsigned long msg,
void *ptr)
{
struct net_device *dev = netdev_notifier_info_to_dev(ptr);
- if (dev->type != ARPHRD_CAN)
+ if (!can_get_ml_priv(dev))
return NOTIFY_DONE;
if (msg != NETDEV_UNREGISTER && msg != NETDEV_DOWN)
return NOTIFY_DONE;
if (unlikely(raw_busy_notifier)) /* Check for reentrant bug. */
return NOTIFY_DONE;
@@ -482,11 +482,11 @@ static int raw_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int len
dev = dev_get_by_index(sock_net(sk), addr->can_ifindex);
if (!dev) {
err = -ENODEV;
goto out;
}
- if (dev->type != ARPHRD_CAN) {
+ if (!can_get_ml_priv(dev)) {
err = -ENODEV;
goto out_put_dev;
}
if (!(dev->flags & IFF_UP))
--
2.53.0
^ permalink raw reply related [flat|nested] 7+ messages in thread* Re: [PATCH v5 2/3] can: convert unreliable ARPHRD_CAN type checks to robust can_get_ml_priv()
2026-09-29 16:34 ` [PATCH v5 2/3] can: convert unreliable ARPHRD_CAN type checks to robust can_get_ml_priv() Oliver Hartkopp
@ 2026-10-03 5:48 ` netdev-bot+sashiko
0 siblings, 0 replies; 7+ messages in thread
From: netdev-bot+sashiko @ 2026-10-03 5:48 UTC (permalink / raw)
To: socketcan; +Cc: linux-can, stable, o.rempel, kuba
Thank you for your contribution! Sashiko AI review found more severe
issue(s) in other patches of this series. This mail is only an FYI, in case
you want to address the nit picks below when you respin.
Low priority / nit picks for your consideration:
- [Low] The commit message does not say what user-visible bug this
stable-tagged patch fixes.
--
can: convert unreliable ARPHRD_CAN type checks to robust can_get_ml_priv()
This patch replaces the dev->type != ARPHRD_CAN checks in af_can, bcm, gw,
isotp and raw with can_get_ml_priv() checks. The stated reason is that
TUNSETLINK lets a down TUN/TAP device change its type to ARPHRD_CAN while
dev->ml_priv stays NULL.
> This has been used directly by the referenced commit in the CAN specific
> j1939 and proc code but not in the other parts of the CAN subsystem.
[Severity: Low]
Is the "not in the other parts of the CAN subsystem" part accurate?
af_can.c already checks can_get_ml_priv() in can_rx_register(), which was
added by commit 8aa59e355949 ("can: af_can: fix NULL pointer dereference
in can_rx_register()"). It is also checked in can_rcv(), canfd_rcv() and
canxl_rcv(). The removed lines in this diff show it:
if (dev && (dev->type != ARPHRD_CAN || !can_get_ml_priv(dev)))
return -ENODEV;
> Instead of checking dev->type being the unreliable ARPHRD_CAN value convert
> the missing "valid CAN devices" checks to can_get_ml_priv().
The patch is tagged for stable, but the message reads like a cleanup.
Could it also describe the user-visible bug being fixed?
Before this patch, a NULL pointer dereference looks reachable through
CAN_ISOTP. isotp_bind() only checked dev->type, so it accepted a TUN
device whose type had been set to ARPHRD_CAN. It also ignores the
-ENODEV that can_rx_register() returns:
if (isotp_register_rxid(so))
can_rx_register(net, dev, rx_id, SINGLE_MASK(rx_id),
isotp_rcv, sk, "isotp", sk);
...
so->bound = 1;
...
so->dev = dev;
On close(), isotp_release() then calls can_rx_unregister() on so->dev.
Before this patch, can_rx_unregister() only checked the type:
if (dev && dev->type != ARPHRD_CAN)
return;
So it carried on into can_dev_rcv_lists_find(), which has no NULL check:
struct can_ml_priv *can_ml = can_get_ml_priv(dev);
return &can_ml->dev_rcv_lists;
dev_rcv_lists is the first member of struct can_ml_priv, so this returns
NULL. The call chain is:
close()
isotp_release()
can_rx_unregister()
can_dev_rcv_lists_find() <- returns NULL
can_rcv_list_find()
hlist_for_each_entry_rcu() <- NULL dereference
isotp_notify() for NETDEV_UNREGISTER reaches the same path. Creating the
TUN device needs CAP_NET_ADMIN, and an unprivileged user can get that
inside a user namespace.
Could the message mention the crash, the affected protocol, and the
trigger (TUNSETLINK to ARPHRD_CAN, then binding a CAN_ISOTP socket)? That
would make it clear to stable backporters that this is a crash fix.
--
Sashiko AI review · https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260929163424.16382-1-socketcan%40hartkopp.net
^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH v5 3/3] can: fix unique skb identifier regression under RPS
2026-09-29 16:34 [PATCH v5 0/3] CAN netlayer fixes for stable Oliver Hartkopp
2026-09-29 16:34 ` [PATCH v5 1/3] can: remove CAN filters independent from namespace Oliver Hartkopp
2026-09-29 16:34 ` [PATCH v5 2/3] can: convert unreliable ARPHRD_CAN type checks to robust can_get_ml_priv() Oliver Hartkopp
@ 2026-09-29 16:34 ` Oliver Hartkopp
2026-10-03 5:48 ` netdev-bot+sashiko
2 siblings, 1 reply; 7+ messages in thread
From: Oliver Hartkopp @ 2026-09-29 16:34 UTC (permalink / raw)
To: linux-can; +Cc: Oliver Hartkopp, Joerg Willmann, stable
Commit d4fb6514ff8e ("can: use skb hash instead of private variable in
headroom") moved the per-skb unique identifier used for raw_rcv()
duplicate detection into skb->hash.
With RPS enabled, get_rps_cpu() calls skb_get_hash() before the frame
reaches the CAN subsystem. Since CAN skbs have no L3/L4 headers, the
flow dissector assigns every CAN frame the same non-zero software
hash. can_set_skb_uid() only generated a new identifier when
skb->hash was 0, so it kept this constant hash. When the SLAB
allocator later reused the same skb address, raw_rcv() mistook the
next legitimate frame for a duplicate and dropped it.
Fix this by storing the CAN UID in the CAN skb extension
(struct can_skb_ext::can_skb_uid) instead of skb->hash, decoupling it
from any hash the network stack may compute. can_set_skb_uid() keeps
its "assign only if unset" behaviour, which preserves UIDs set before
transmission (e.g. by isotp to identify echo frames) across the local
loopback path.
Frames whose extension is still shared with another clone (e.g. via
tc mirred or netem duplicate) are given a private extension copy
before the UID is assigned, so that independently received clones
never end up with the same UID.
can-gw and vxcan additionally clear the UID of forwarded/duplicated
frames so each newly routed frame gets its own unique identifier.
Fixes: d4fb6514ff8e ("can: use skb hash instead of private variable in headroom")
Reported-by: Joerg Willmann <joe@clnt.de>
Closes: https://lore.kernel.org/linux-can/2859AD3D-C805-41A0-9036-C5E8EE152419@clnt.de/
Cc: stable@vger.kernel.org
Tested-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
v2: We need a non-zero UID for the cfecho checks in isotp.c
So restore the former while (!(skb->hash)) statement
v3: omit the problematic use of skb->hash reported by sashiko bot
v4: address tc mirred or netem duplicate clones suggested by sashiko bot
v5: remove the skb_clone() test speed-up as it introduces a bug
---
drivers/net/can/vxcan.c | 3 +++
include/linux/can/core.h | 3 ++-
include/linux/can/skb.h | 4 +++-
include/net/can.h | 2 ++
net/can/af_can.c | 50 +++++++++++++++++++++++++++++-----------
net/can/gw.c | 3 +++
net/can/isotp.c | 16 ++++++++-----
net/can/raw.c | 10 +++++---
8 files changed, 66 insertions(+), 25 deletions(-)
diff --git a/drivers/net/can/vxcan.c b/drivers/net/can/vxcan.c
index 9e2e25d02471..51148a81d1d9 100644
--- a/drivers/net/can/vxcan.c
+++ b/drivers/net/can/vxcan.c
@@ -77,10 +77,13 @@ static netdev_tx_t vxcan_xmit(struct sk_buff *oskb, struct net_device *dev)
goto out_unlock;
}
/* reset CAN GW hop counter */
csx->can_gw_hops = 0;
+ /* start with new CAN skb UID in the other namespace */
+ csx->can_skb_uid = 0;
+
skb->pkt_type = PACKET_BROADCAST;
skb->dev = peer;
skb->ip_summed = CHECKSUM_UNNECESSARY;
len = can_skb_get_data_len(skb);
diff --git a/include/linux/can/core.h b/include/linux/can/core.h
index 3287232e3cad..2de74c2b78b6 100644
--- a/include/linux/can/core.h
+++ b/include/linux/can/core.h
@@ -15,10 +15,11 @@
#define _CAN_CORE_H
#include <linux/can.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
+#include <net/can.h>
#define DNAME(dev) ((dev) ? (dev)->name : "any")
/**
* struct can_proto - CAN protocol structure
@@ -56,9 +57,9 @@ extern void can_rx_unregister(struct net *net, struct net_device *dev,
canid_t can_id, canid_t mask,
void (*func)(struct sk_buff *, void *),
void *data);
extern int can_send(struct sk_buff *skb, int loop);
-void can_set_skb_uid(struct sk_buff *skb);
+void can_set_skb_uid(struct can_skb_ext *csx);
void can_sock_destruct(struct sock *sk);
#endif /* !_CAN_CORE_H */
diff --git a/include/linux/can/skb.h b/include/linux/can/skb.h
index a70a02967071..5d27843862fc 100644
--- a/include/linux/can/skb.h
+++ b/include/linux/can/skb.h
@@ -41,12 +41,14 @@ bool can_dropped_invalid_skb(struct net_device *dev, struct sk_buff *skb);
static inline struct can_skb_ext *can_skb_ext_add(struct sk_buff *skb)
{
struct can_skb_ext *csx = skb_ext_add(skb, SKB_EXT_CAN);
/* skb_ext_add() returns uninitialized space */
- if (csx)
+ if (csx) {
csx->can_gw_hops = 0;
+ csx->can_skb_uid = 0;
+ }
return csx;
}
static inline struct can_skb_ext *can_skb_ext_find(struct sk_buff *skb)
diff --git a/include/net/can.h b/include/net/can.h
index 6db9e826f0e0..2b8af2598732 100644
--- a/include/net/can.h
+++ b/include/net/can.h
@@ -15,14 +15,16 @@
* struct can_skb_ext - skb extensions for CAN specific content
* @can_iif: ifindex of the first interface the CAN frame appeared on
* @can_framelen: cached echo CAN frame length for bql
* @can_gw_hops: can-gw CAN frame time-to-live counter
* @can_ext_flags: CAN skb extensions flags
+ * @can_skb_uid: CAN skb UID for raw_rcv and isotp echo handling
*/
struct can_skb_ext {
int can_iif;
u16 can_framelen;
u8 can_gw_hops;
u8 can_ext_flags;
+ u32 can_skb_uid;
};
#endif /* _NET_CAN_H */
diff --git a/net/can/af_can.c b/net/can/af_can.c
index ef435f22ac93..dc27ace43719 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -639,17 +639,14 @@ static int can_rcv_filter(struct can_dev_rcv_lists *dev_rcv_lists, struct sk_buf
}
return matches;
}
-void can_set_skb_uid(struct sk_buff *skb)
+void can_set_skb_uid(struct can_skb_ext *csx)
{
- /* create non-zero unique skb identifier together with *skb */
- while (!(skb->hash))
- skb->hash = atomic_inc_return(&skbcounter);
-
- skb->sw_hash = 1;
+ while (!(csx->can_skb_uid))
+ csx->can_skb_uid = atomic_inc_return(&skbcounter);
}
EXPORT_SYMBOL(can_set_skb_uid);
static void can_receive(struct sk_buff *skb, struct net_device *dev)
{
@@ -660,12 +657,10 @@ static void can_receive(struct sk_buff *skb, struct net_device *dev)
/* update statistics */
atomic_long_inc(&pkg_stats->rx_frames);
atomic_long_inc(&pkg_stats->rx_frames_delta);
- can_set_skb_uid(skb);
-
rcu_read_lock();
/* deliver the packet to sockets listening on all devices */
matches = can_rcv_filter(net->can.rx_alldev_list, skb);
@@ -685,51 +680,78 @@ static void can_receive(struct sk_buff *skb, struct net_device *dev)
}
static int can_rcv(struct sk_buff *skb, struct net_device *dev,
struct packet_type *pt, struct net_device *orig_dev)
{
- if (unlikely(!can_get_ml_priv(dev) ||
- !can_skb_ext_find(skb) || !can_is_can_skb(skb))) {
+ struct can_skb_ext *csx = can_skb_ext_find(skb);
+
+ if (unlikely(!can_get_ml_priv(dev) || !csx || !can_is_can_skb(skb))) {
pr_warn_once("PF_CAN: dropped non conform CAN skbuff: dev type %d, len %d\n",
dev->type, skb->len);
kfree_skb_reason(skb, SKB_DROP_REASON_CAN_RX_INVALID_FRAME);
return NET_RX_DROP;
}
+ /* create unshared CAN skb_extension for netem/mirred skb clones */
+ csx = skb_ext_add(skb, SKB_EXT_CAN);
+ if (unlikely(!csx)) {
+ kfree_skb_reason(skb, SKB_DROP_REASON_NOMEM);
+ return NET_RX_DROP;
+ }
+
+ can_set_skb_uid(csx);
can_receive(skb, dev);
return NET_RX_SUCCESS;
}
static int canfd_rcv(struct sk_buff *skb, struct net_device *dev,
struct packet_type *pt, struct net_device *orig_dev)
{
- if (unlikely(!can_get_ml_priv(dev) ||
- !can_skb_ext_find(skb) || !can_is_canfd_skb(skb))) {
+ struct can_skb_ext *csx = can_skb_ext_find(skb);
+
+ if (unlikely(!can_get_ml_priv(dev) || !csx || !can_is_canfd_skb(skb))) {
pr_warn_once("PF_CAN: dropped non conform CAN FD skbuff: dev type %d, len %d\n",
dev->type, skb->len);
kfree_skb_reason(skb, SKB_DROP_REASON_CANFD_RX_INVALID_FRAME);
return NET_RX_DROP;
}
+ /* create unshared CAN skb_extension for netem/mirred skb clones */
+ csx = skb_ext_add(skb, SKB_EXT_CAN);
+ if (unlikely(!csx)) {
+ kfree_skb_reason(skb, SKB_DROP_REASON_NOMEM);
+ return NET_RX_DROP;
+ }
+
+ can_set_skb_uid(csx);
can_receive(skb, dev);
return NET_RX_SUCCESS;
}
static int canxl_rcv(struct sk_buff *skb, struct net_device *dev,
struct packet_type *pt, struct net_device *orig_dev)
{
- if (unlikely(!can_get_ml_priv(dev) ||
- !can_skb_ext_find(skb) || !can_is_canxl_skb(skb))) {
+ struct can_skb_ext *csx = can_skb_ext_find(skb);
+
+ if (unlikely(!can_get_ml_priv(dev) || !csx || !can_is_canxl_skb(skb))) {
pr_warn_once("PF_CAN: dropped non conform CAN XL skbuff: dev type %d, len %d\n",
dev->type, skb->len);
kfree_skb_reason(skb, SKB_DROP_REASON_CANXL_RX_INVALID_FRAME);
return NET_RX_DROP;
}
+ /* create unshared CAN skb_extension for netem/mirred skb clones */
+ csx = skb_ext_add(skb, SKB_EXT_CAN);
+ if (unlikely(!csx)) {
+ kfree_skb_reason(skb, SKB_DROP_REASON_NOMEM);
+ return NET_RX_DROP;
+ }
+
+ can_set_skb_uid(csx);
can_receive(skb, dev);
return NET_RX_SUCCESS;
}
/* af_can protocol functions */
diff --git a/net/can/gw.c b/net/can/gw.c
index d9912dea738b..54bb5bd3242a 100644
--- a/net/can/gw.c
+++ b/net/can/gw.c
@@ -526,10 +526,13 @@ static void can_can_gw_rcv(struct sk_buff *skb, void *data)
}
/* put the incremented hop counter in the cloned skb */
ncsx->can_gw_hops = csx->can_gw_hops + 1;
+ /* force a new CAN UID generation for the routed frame */
+ ncsx->can_skb_uid = 0;
+
/* first processing of this CAN frame -> adjust to private hop limit */
if (gwj->limit_hops && ncsx->can_gw_hops == 1)
ncsx->can_gw_hops = max_hops - gwj->limit_hops + 1;
nskb->dev = gwj->dst.dev;
diff --git a/net/can/isotp.c b/net/can/isotp.c
index d3f79efc9c1e..860c5221e299 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -890,11 +890,11 @@ static void isotp_send_cframe(struct isotp_sock *so)
}
csx->can_iif = dev->ifindex;
/* set uid in tx skb to identify CF echo frames */
- can_set_skb_uid(skb);
+ can_set_skb_uid(csx);
cf = (struct canfd_frame *)skb->data;
skb_put_zero(skb, so->ll.mtu);
/* create consecutive frame */
@@ -916,11 +916,11 @@ static void isotp_send_cframe(struct isotp_sock *so)
old_cfecho = READ_ONCE(so->cfecho);
if (old_cfecho)
pr_notice_once("can-isotp: cfecho is %08X != 0\n", old_cfecho);
/* set consecutive frame echo tag */
- WRITE_ONCE(so->cfecho, skb->hash);
+ WRITE_ONCE(so->cfecho, csx->can_skb_uid);
/* send frame with local echo enabled */
can_send_ret = can_send(skb, 1);
if (can_send_ret) {
pr_notice_once("can-isotp: %s: can_send_ret %pe\n",
@@ -968,22 +968,26 @@ static void isotp_create_fframe(struct canfd_frame *cf, struct isotp_sock *so,
static void isotp_rcv_echo(struct sk_buff *skb, void *data)
{
struct sock *sk = (struct sock *)data;
struct isotp_sock *so = isotp_sk(sk);
+ struct can_skb_ext *csx = can_skb_ext_find(skb);
/* only handle my own local echo CF/SF skb's (no FF!) */
if (skb->sk != sk)
return;
+ if (WARN_ON_ONCE(!csx))
+ return;
+
/* unlike isotp_rcv_fc()/isotp_rcv_cf(), not already under so->rx_lock
* (no isotp_rcv() caller here), so take it ourselves
*/
spin_lock(&so->rx_lock);
/* so->cfecho may since belong to a new transfer; recheck under lock */
- if (READ_ONCE(so->cfecho) != skb->hash)
+ if (READ_ONCE(so->cfecho) != csx->can_skb_uid)
goto out_unlock;
/* cancel local echo timeout */
hrtimer_cancel(&so->echotimer);
@@ -1221,11 +1225,11 @@ static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
}
csx->can_iif = dev->ifindex;
/* set uid in tx skb to identify CF echo frames */
- can_set_skb_uid(skb);
+ can_set_skb_uid(csx);
so->tx.len = size;
so->tx.idx = 0;
cf = (struct canfd_frame *)skb->data;
@@ -1260,11 +1264,11 @@ static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
cf->data[SF_PCI_SZ4 + ae] = size;
else
cf->data[ae] |= size;
/* set CF echo tag for isotp_rcv_echo() (SF-mode) */
- WRITE_ONCE(so->cfecho, skb->hash);
+ WRITE_ONCE(so->cfecho, csx->can_skb_uid);
} else {
/* send first frame */
isotp_create_fframe(cf, so, ae);
@@ -1277,11 +1281,11 @@ static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
/* disable wait for FCs due to activated block size */
so->txfc.bs = 0;
/* set CF echo tag for isotp_rcv_echo() (CF-mode) */
- WRITE_ONCE(so->cfecho, skb->hash);
+ WRITE_ONCE(so->cfecho, csx->can_skb_uid);
} else {
/* standard flow control check */
new_state = ISOTP_WAIT_FIRST_FC;
/* start timeout for FC */
diff --git a/net/can/raw.c b/net/can/raw.c
index 7c48ff36e6cd..7873bfc584ef 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -75,11 +75,11 @@ MODULE_ALIAS("can-proto-1");
* storing the single filter in dfilter, to avoid using dynamic memory.
*/
struct uniqframe {
const struct sk_buff *skb;
- u32 hash;
+ u32 can_skb_uid;
unsigned int join_rx_count;
};
struct raw_sock {
struct sock sk;
@@ -131,16 +131,20 @@ static void raw_rcv(struct sk_buff *oskb, void *data)
struct sock *sk = (struct sock *)data;
struct raw_sock *ro = raw_sk(sk);
enum skb_drop_reason reason;
struct sockaddr_can *addr;
struct sk_buff *skb;
+ struct can_skb_ext *csx = can_skb_ext_find(oskb);
unsigned int *pflags;
/* check the received tx sock reference */
if (!ro->recv_own_msgs && oskb->sk == sk)
return;
+ if (WARN_ON_ONCE(!csx))
+ return;
+
/* make sure to not pass oversized frames to the socket */
if (!ro->fd_frames && can_is_canfd_skb(oskb))
return;
if (can_is_canxl_skb(oskb)) {
@@ -163,21 +167,21 @@ static void raw_rcv(struct sk_buff *oskb, void *data)
}
}
/* eliminate multiple filter matches for the same skb */
if (this_cpu_ptr(ro->uniq)->skb == oskb &&
- this_cpu_ptr(ro->uniq)->hash == oskb->hash) {
+ this_cpu_ptr(ro->uniq)->can_skb_uid == csx->can_skb_uid) {
if (!ro->join_filters)
return;
this_cpu_inc(ro->uniq->join_rx_count);
/* drop frame until all enabled filters matched */
if (this_cpu_ptr(ro->uniq)->join_rx_count < ro->count)
return;
} else {
this_cpu_ptr(ro->uniq)->skb = oskb;
- this_cpu_ptr(ro->uniq)->hash = oskb->hash;
+ this_cpu_ptr(ro->uniq)->can_skb_uid = csx->can_skb_uid;
this_cpu_ptr(ro->uniq)->join_rx_count = 1;
/* drop first frame to check all enabled filters? */
if (ro->join_filters && ro->count > 1)
return;
}
--
2.53.0
^ permalink raw reply related [flat|nested] 7+ messages in thread* Re: [PATCH v5 3/3] can: fix unique skb identifier regression under RPS
2026-09-29 16:34 ` [PATCH v5 3/3] can: fix unique skb identifier regression under RPS Oliver Hartkopp
@ 2026-10-03 5:48 ` netdev-bot+sashiko
0 siblings, 0 replies; 7+ messages in thread
From: netdev-bot+sashiko @ 2026-10-03 5:48 UTC (permalink / raw)
To: socketcan; +Cc: linux-can, stable, o.rempel, kuba
Thank you for your contribution! Sashiko AI review found 1 potential
issue(s) to consider.
Critical: 0 · High: 0 · Medium: 1 · Low: 0
If you believe none of the issues are legitimate, please reply to each
issue of Medium severity or higher and explain why the AI is wrong.
If any of them are legitimate and you plan to respin, please let patchwork
know by including "pw-bot: cr" as a separate line at the end of your reply
(one such reply per series is enough).
- [Medium] The commit message says that frames sharing an extension with
another clone (tc mirred, netem duplicate) get a private copy before…
--
can: fix unique skb identifier regression under RPS
This commit moves the CAN per-skb unique identifier that raw_rcv() uses
for duplicate detection out of skb->hash and into a new can_skb_uid field
in struct can_skb_ext. The receive handlers now give a shared extension a
private copy before they assign the UID, and can-gw and vxcan clear the
UID on forwarded frames.
Closes: https://lore.kernel.org/linux-can/2859AD3D-C805-41A0-9036-C5E8EE152419@clnt.de/
> diff --git a/net/can/af_can.c b/net/can/af_can.c
> index ef435f22ac933..dc27ace43719d 100644
> --- a/net/can/af_can.c
> +++ b/net/can/af_can.c
> @@ -641,13 +641,10 @@ static int can_rcv_filter(struct can_dev_rcv_lists *dev_rcv_lists, struct sk_buf
> return matches;
> }
>
> -void can_set_skb_uid(struct sk_buff *skb)
> +void can_set_skb_uid(struct can_skb_ext *csx)
> {
> - /* create non-zero unique skb identifier together with *skb */
> - while (!(skb->hash))
> - skb->hash = atomic_inc_return(&skbcounter);
> -
> - skb->sw_hash = 1;
> + while (!(csx->can_skb_uid))
> + csx->can_skb_uid = atomic_inc_return(&skbcounter);
> }
> EXPORT_SYMBOL(can_set_skb_uid);
[ ... ]
> @@ -696,6 +692,14 @@ static int can_rcv(struct sk_buff *skb, struct net_device *dev,
> return NET_RX_DROP;
> }
>
> + /* create unshared CAN skb_extension for netem/mirred skb clones */
> + csx = skb_ext_add(skb, SKB_EXT_CAN);
> + if (unlikely(!csx)) {
> + kfree_skb_reason(skb, SKB_DROP_REASON_NOMEM);
> + return NET_RX_DROP;
> + }
> +
> + can_set_skb_uid(csx);
[Severity: Medium]
Do independently received clones get different UIDs if the UID was already
set before the clone was made? The same question applies to canfd_rcv()
and canxl_rcv().
The commit message says:
Frames whose extension is still shared with another clone (e.g. via
tc mirred or netem duplicate) are given a private extension copy
before the UID is assigned, so that independently received clones
never end up with the same UID.
skb_ext_add() copies the shared extension through skb_ext_maybe_cow(),
which is a memcpy(). Any non-zero can_skb_uid that is already set ends up
in the private copy. can_set_skb_uid() then keeps that value, because it
only assigns a UID when the value is 0.
isotp sets a non-zero UID before transmission, in both isotp_sendmsg()
and isotp_send_cframe():
/* set uid in tx skb to identify CF echo frames */
can_set_skb_uid(csx);
...
can_send(skb, 1);
Suppose that TX skb is duplicated on egress. netem_enqueue() calls
skb2 = skb_clone(skb, GFP_ATOMIC) for duplicates, and mirred egress
mirroring also clones. Every copy then has the same UID X. Could the
following happen on an IFF_ECHO device such as vcan with echo=1?
vcan_tx(skb)
can_create_echo_skb()
nskb = skb_clone(skb) /* echo e1, UID X */
consume_skb(skb)
netif_rx(e1)
can_rcv(e1)
raw_rcv() /* per-cpu uniq = {e1, X} */
can_receive()
consume_skb(e1) /* e1 slab slot freed */
netem watchdog dequeues skb2
vcan_tx(skb2)
can_create_echo_skb()
nskb = skb_clone(skb2) /* e2 reuses e1's slot, UID X */
netif_rx(e2)
can_rcv(e2)
raw_rcv()
The check in raw_rcv() would then match:
if (this_cpu_ptr(ro->uniq)->skb == oskb &&
this_cpu_ptr(ro->uniq)->can_skb_uid == csx->can_skb_uid) {
if (!ro->join_filters)
return;
The duplicated frame would be silently dropped for every raw socket that
already received e1. With join_filters set, join_rx_count would be
counted too high instead.
This is the same false duplicate drop that the patch fixes for skb->hash.
Here it is limited to frames with a UID set before transmission. The old
skb->hash scheme behaved the same way in this case, because skb_clone()
copies the hash. can-gw and vxcan clear the UID explicitly, but generic
clone paths such as netem and mirred do not.
Clearing the UID whenever the extension is shared would not fix this
either. For devices without IFF_ECHO, can_send() does the loopback with
newskb = skb_clone(skb) while the original skb is still alive. isotp echo
matching depends on that clone keeping the UID.
Should the commit message be toned down for this case, or is there
another way to tell these clones apart?
> can_receive(skb, dev);
> return NET_RX_SUCCESS;
> }
--
Sashiko AI review · https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260929163424.16382-1-socketcan%40hartkopp.net
^ permalink raw reply [flat|nested] 7+ messages in thread