[PATCH net-next 0/11] pull-request: can-next 2026-10-19

[PATCH net-next 0/11] pull-request: can-next 2026-10-19

[Marc Kleine-Budde]

Hello netdev-team,

this is a pull request of 11 patches for net-next/main and obsoletes
pull-request: can-next 2026-10-18.

The first patch is by Vincent Mailhol and drops CAN-XL frames on non
CAN-XL devices.

A patch by Sang-Heon Jeon removes a redundant NULL check before
netdev_hold() in the CAN RAW protocol.

A patch by Kaixuan Li for the CAN ISOTP protocol improves the check
for the correct CAN CC/FD frames.

The next 3 patches are by Cunhao Lu and make CAN skb freeing safe in
any context in several CAN helper functions.

A series by Oliver Hartkopp et al fixes several problems in the CAN
net-layer:

3 patches target the CAN procfs: A patch by Runyu Xiao resets the CAN
pkg_stats using atomics, a patch by Oliver Hartkopp fixes the stats
calculation after a statistics reset. Followed by a patch to remove
kernel pointers from the output.

The last s patches are by Oliver Hartkopp as well, they convert the
unreliable ARPHRD_CAN type check to the robust can_get_ml_priv() and
protect the CAN receive lists with a per-device lock.

regards,
Marc

---

The following changes since commit 98c2ad4f5d805dbc1ea436a334ee59311806a48c:

  Merge branch 'ipv4-remove-netns-argument-from-fib_table_lookup' (2026-10-16 18:52:36 -0700)

are available in the Git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/mkl/linux-can-next.git tags/linux-can-next-for-7.4-20261019

for you to fetch changes up to 94f33aab0beb5c7eba56be9fab2032b82fa78b86:

  Merge patch series "can: protect the receive lists with a per-device lock" (2026-10-19 18:46:56 +0200)

----------------------------------------------------------------
linux-can-next-for-7.4-20261019

----------------------------------------------------------------
Cunhao Lu (3):
      can: skb: make echo skb freeing safe in any IRQ context
      can: skb: make CAN skb allocation failure paths IRQ-safe
      can: dev: can_put_echo_skb(): free skb on invalid echo index

Kaixuan Li (1):
      can: isotp: check the frame type, not just the length

Marc Kleine-Budde (2):
      Merge patch series "can: skb: make echo skb freeing safe in any IRQ context"
      Merge patch series "can: protect the receive lists with a per-device lock"

Oliver Hartkopp (4):
      can: proc: skip stats calculation after reset in can_stat_update()
      can: proc: remove pointers from CAN specific proc output
      can: replace ARPHRD_CAN type checks with can_get_ml_priv()
      can: protect the receive lists with a per-device lock

Runyu Xiao (1):
      can: proc: reset pkg_stats atomics individually

Sang-Heon Jeon (1):
      can: raw: remove redundant NULL check before netdev_hold()

Vincent Mailhol (1):
      can: dev: can_dropped_invalid_skb: drop CAN XL frames on non-CAN XL devices

 Documentation/networking/can.rst |  16 ++--
 drivers/net/can/dev/skb.c        |  16 ++--
 include/linux/can/can-ml.h       |   3 +
 include/linux/can/core.h         |   2 +-
 include/linux/can/dev.h          |   2 +-
 include/linux/can/skb.h          |   4 +-
 include/net/netns/can.h          |   2 +-
 net/can/af_can.c                 |  61 +++++++++-------
 net/can/af_can.h                 |   2 +-
 net/can/bcm.c                    |  64 ++++++----------
 net/can/gw.c                     |   9 ++-
 net/can/isotp.c                  |  57 +++++++++++----
 net/can/j1939/main.c             |   2 +-
 net/can/proc.c                   |  95 ++++++++++++++----------
 net/can/raw.c                    | 153 +++++++++++++++++++++++++--------------
 15 files changed, 286 insertions(+), 202 deletions(-)

[PATCH net-next 01/11] can: dev: can_dropped_invalid_skb: drop CAN XL frames on non-CAN XL devices

[Marc Kleine-Budde]

From: Vincent Mailhol <mailhol@kernel.org>

Sending a PF_PACKET bypasses the CAN framework logic and can directly
reach a CAN driver's xmit() function. The PF_PACKET framework only
checks that skb->len does not exceed the net_device MTU.

For a CAN device that is not CAN XL capable, anything above CANFD_MTU
(72 bytes) is therefore dropped before it reaches the driver. However,
CAN XL frames are variable length. can_is_canxl_skb() accepts lengths in
the range CANXL_HDR_SIZE + CANXL_MIN_DLEN up to CANXL_MTU, i.e. 13 to
2060 bytes.

As a result, an ETH_P_CANXL skb with a length between 13 and 72 bytes
can pass both the MTU and the can_dropped_invalid_skb() checks.

A driver that does not support CAN XL will interpret canxl_frame->flags
as a length because of the overlap with can_frame->len. And because
CANXL_XLF is set, the resulting length is between 128 and 255. For
drivers that do not check can_frame->len before copying can_frame->data,
as most drivers do, this results in a buffer overflow of up to 247
bytes.

Drop ETH_P_CANXL skbs if the device does not have the CAN_CAP_XL
capability. Keep can_is_canxl_skb() for the validation of CAN XL skbs.

Closes: https://sashiko.dev/#/patchset/20260731-master-v5-0-5b27029dee20@qq.com?part=1
Fixes: fb08cba12b52 ("can: canxl: update CAN infrastructure for CAN XL frames")
Signed-off-by: Vincent Mailhol <mailhol@kernel.org>
Link: https://patch.msgid.link/20260731-drop_canxl_frames-v1-1-7387b70353b3@kernel.org
Cc: stable@kernel.org
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/net/can/dev/skb.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c
index 14edec5afb57..bc0787535b52 100644
--- a/drivers/net/can/dev/skb.c
+++ b/drivers/net/can/dev/skb.c
@@ -4,6 +4,7 @@
  * Copyright (C) 2008-2009 Wolfgang Grandegger <wg@grandegger.com>
  */
 
+#include <linux/can/can-ml.h>
 #include <linux/can/dev.h>
 #include <linux/module.h>
 #include <net/can.h>
@@ -388,7 +389,7 @@ bool can_dropped_invalid_skb(struct net_device *dev, struct sk_buff *skb)
 		break;
 
 	case ETH_P_CANXL:
-		if (!can_is_canxl_skb(skb))
+		if (!can_cap_enabled(dev, CAN_CAP_XL) || !can_is_canxl_skb(skb))
 			goto inval_skb;
 		break;
 

base-commit: 98c2ad4f5d805dbc1ea436a334ee59311806a48c
-- 
2.53.0

Re: [PATCH net-next 01/11] can: dev: can_dropped_invalid_skb: drop CAN XL frames on non-CAN XL devices

[netdev-bot+sinfo]

Hi!

This is an automated message. This series looks like a fix, but its
commit messages seem to be missing some information:

 - How the issue was discovered, e.g. hit in production, hit during
   development, syzbot report, manual code inspection, LLM or static
   analysis tool scan.

 - Whether the issue was actually triggered, or is only theoretical
   (e.g. found by code inspection). If it was triggered please include
   the symptoms, like the stack trace or error messages.

Please do not repost the series just to address the above. Instead,
reply to this email with the missing information, so that reviewers
can take it into account. If the series needs another revision for
other reasons, please include the information in the commit messages
then.

The evaluation is done by an LLM so it may be wrong, if you think
that is the case please reply and explain.

[PATCH net-next 02/11] can: raw: remove redundant NULL check before netdev_hold()

[Marc Kleine-Budde]

From: Sang-Heon Jeon <ekffu200098@gmail.com>

netdev_hold() does nothing if dev is NULL, so the check before the call
is redundant.

So remove it. No functional change.

This is the result of running the Coccinelle script from
scripts/coccinelle/free/ifnulldev_put.cocci after commit f83b8a58695c
("coccinelle: ifnulldev_put: update outdated helper names").

Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://patch.msgid.link/20260831052031.902699-1-ekffu200098@gmail.com
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 net/can/raw.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/can/raw.c b/net/can/raw.c
index 0acd4f6c6dd6..6944ebab3feb 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -529,8 +529,7 @@ static int raw_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int len
 		ro->bound = 1;
 		/* bind() ok -> hold a reference for new ro->dev */
 		ro->dev = dev;
-		if (ro->dev)
-			netdev_hold(ro->dev, &ro->dev_tracker, GFP_KERNEL);
+		netdev_hold(ro->dev, &ro->dev_tracker, GFP_KERNEL);
 	}
 
 out_put_dev:
-- 
2.53.0

[PATCH net-next 03/11] can: skb: make echo skb freeing safe in any IRQ context

[Marc Kleine-Budde]

From: Cunhao Lu <1579567540@qq.com>

can_put_echo_skb() can be called with hardware interrupts disabled. Its
direct drop paths use kfree_skb(), while can_create_echo_skb() uses
kfree_skb() when cloning fails and consume_skb() after a successful clone.
None of these helpers is safe in every IRQ context.

Use dev_kfree_skb_any() for all drop paths and dev_consume_skb_any() when
consuming a successfully cloned skb. This preserves the respective skb drop
and consumed semantics regardless of the caller IRQ context.

Signed-off-by: Cunhao Lu <1579567540@qq.com>
Link: https://patch.msgid.link/tencent_E84809CF236D0137885E7E4E4D58340B3208@qq.com
Cc: stable@kernel.org
Fixes: ae64438be192 ("can: dev: fix skb drop check")
Fixes: 0ae89beb283a ("can: add destructor for self generated skbs")
Fixes: 3ccd4c6167d3 ("can: Unify droping of invalid tx skbs and netdev stats")
Fixes: 39549eef3587 ("can: CAN Network device driver and Netlink interface")
[mkl: also convert can_dropped_invalid_skb(), can_dev_dropped_skb()]
[mkl: add stable on Cc + add Fixes tags]
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/net/can/dev/skb.c | 6 +++---
 include/linux/can/dev.h   | 2 +-
 include/linux/can/skb.h   | 4 ++--
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c
index bc0787535b52..46c151eece8f 100644
--- a/drivers/net/can/dev/skb.c
+++ b/drivers/net/can/dev/skb.c
@@ -63,7 +63,7 @@ int can_put_echo_skb(struct sk_buff *skb, struct net_device *dev,
 	    (skb->protocol != htons(ETH_P_CAN) &&
 	     skb->protocol != htons(ETH_P_CANFD) &&
 	     skb->protocol != htons(ETH_P_CANXL))) {
-		kfree_skb(skb);
+		dev_kfree_skb_any(skb);
 		return 0;
 	}
 
@@ -91,7 +91,7 @@ int can_put_echo_skb(struct sk_buff *skb, struct net_device *dev,
 	} else {
 		/* locking problem with netif_stop_queue() ?? */
 		netdev_err(dev, "%s: BUG! echo_skb %d is occupied!\n", __func__, idx);
-		kfree_skb(skb);
+		dev_kfree_skb_any(skb);
 		return -EBUSY;
 	}
 
@@ -403,7 +403,7 @@ bool can_dropped_invalid_skb(struct net_device *dev, struct sk_buff *skb)
 	return false;
 
 inval_skb:
-	kfree_skb(skb);
+	dev_kfree_skb_any(skb);
 	dev->stats.tx_dropped++;
 	return true;
 }
diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h
index 6d0710d6f571..346faddee02e 100644
--- a/include/linux/can/dev.h
+++ b/include/linux/can/dev.h
@@ -176,7 +176,7 @@ static inline bool can_dev_dropped_skb(struct net_device *dev, struct sk_buff *s
 	return can_dropped_invalid_skb(dev, skb);
 
 invalid_skb:
-	kfree_skb(skb);
+	dev_kfree_skb_any(skb);
 	dev->stats.tx_dropped++;
 	return true;
 }
diff --git a/include/linux/can/skb.h b/include/linux/can/skb.h
index 5d27843862fc..87ace09c0d8b 100644
--- a/include/linux/can/skb.h
+++ b/include/linux/can/skb.h
@@ -78,12 +78,12 @@ static inline struct sk_buff *can_create_echo_skb(struct sk_buff *skb)
 
 	nskb = skb_clone(skb, GFP_ATOMIC);
 	if (unlikely(!nskb)) {
-		kfree_skb(skb);
+		dev_kfree_skb_any(skb);
 		return NULL;
 	}
 
 	can_skb_set_owner(nskb, skb->sk);
-	consume_skb(skb);
+	dev_consume_skb_any(skb);
 	return nskb;
 }
 
-- 
2.53.0

[PATCH net-next 04/11] can: skb: make CAN skb allocation failure paths IRQ-safe

[Marc Kleine-Budde]

From: Cunhao Lu <1579567540@qq.com>

The CAN skb allocation helpers are used from hardware interrupt receive
handlers. If can_skb_ext_add() fails, they release the newly allocated skb
with kfree_skb(), which is not safe in hardware interrupt context.

Use dev_kfree_skb_any() for the allocation failure paths in
alloc_can_skb(), alloc_canfd_skb(), and alloc_canxl_skb().

Fixes: 96ea3a1e2d31 ("can: add CAN skb extension infrastructure")
Signed-off-by: Cunhao Lu <1579567540@qq.com>
Link: https://patch.msgid.link/tencent_C825C17D442F801351CE2FBC4984064B4605@qq.com
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/net/can/dev/skb.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c
index 46c151eece8f..3e36c0368bae 100644
--- a/drivers/net/can/dev/skb.c
+++ b/drivers/net/can/dev/skb.c
@@ -228,7 +228,7 @@ struct sk_buff *alloc_can_skb(struct net_device *dev, struct can_frame **cf)
 
 	csx = can_skb_ext_add(skb);
 	if (!csx) {
-		kfree_skb(skb);
+		dev_kfree_skb_any(skb);
 		goto out_error_cc;
 	}
 
@@ -259,7 +259,7 @@ struct sk_buff *alloc_canfd_skb(struct net_device *dev,
 
 	csx = can_skb_ext_add(skb);
 	if (!csx) {
-		kfree_skb(skb);
+		dev_kfree_skb_any(skb);
 		goto out_error_fd;
 	}
 
@@ -297,7 +297,7 @@ struct sk_buff *alloc_canxl_skb(struct net_device *dev,
 
 	csx = can_skb_ext_add(skb);
 	if (!csx) {
-		kfree_skb(skb);
+		dev_kfree_skb_any(skb);
 		goto out_error_xl;
 	}
 
-- 
2.53.0

[PATCH net-next 05/11] can: dev: can_put_echo_skb(): free skb on invalid echo index

[Marc Kleine-Budde]

From: Cunhao Lu <1579567540@qq.com>

can_put_echo_skb() consumes the skb on all paths except when the echo
index is out of bounds. This leaves ownership with the caller on -EINVAL,
unlike the other error paths, and can leak the skb if the caller expects
consistent semantics.

Free the skb before returning -EINVAL so that all return paths consume it.

Fixes: 6411959c10fe ("can: dev: can_put_echo_skb(): don't crash kernel if can_priv::echo_skb is accessed out of bounds")
Cc: stable@vger.kernel.org
Reviewed-by: Vincent Mailhol <mailhol@kernel.org>
Signed-off-by: Cunhao Lu <1579567540@qq.com>
Link: https://patch.msgid.link/tencent_683AA16E643DE00211CD2FB62991264DC605@qq.com
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

---

FAQ:

Q: `can_skb_init_valid()` directly modifies `skb->data` without checking if
   the SKB is cloned or shared. Is this violating SKB shared buffer rules and
   causing data corruption?

A: The finding about can_skb_init_valid() modifying skb->data on a
   potentially shared buffer is not relevant for this (correct) patch.

   The FDF-flag write in can_skb_init_valid() only matters for PF_PACKET
   use: PF_CAN allocators already set CANFD_FDF. The write exists to
   normalize frames for PF_PACKET observers (tcpdump/Wireshark) so they can
   distinguish classic CAN from CAN FD at the netdev level, and to
   compensate for PF_PACKET senders that omit the bit. That normalization
   is functionally required.

   The shared-buffer concern only becomes realistic through a specific
   chain: a PF_PACKET sender injects a CANFD-sized frame, the CAN driver's
   loopback puts an echo skb back into can_rcv(), and cgw (without
   modfuncs) clones it for forwarding to another interface. Only on that
   second can_skb_init_valid() call is the skb cloned. By then the bit was
   already set on the exclusive skb during the initial xmit path, so the
   flags |= CANFD_FDF write is strictly idempotent for any parallel
   consumer of the shared buffer - no memory-safety or
   information-disclosure consequence. It's a formal violation of the skb
   sharing rules without an observable effect, so the current code can stay
   as-is.

Link: https://lore.kernel.org/all/54a3cc01-abcf-4a33-b932-39bb1f68cdd5@hartkopp.net/
[mkl: convert Oliver's mail to FAQ section]
---
 drivers/net/can/dev/skb.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c
index 3e36c0368bae..738d5968dfa6 100644
--- a/drivers/net/can/dev/skb.c
+++ b/drivers/net/can/dev/skb.c
@@ -55,6 +55,7 @@ int can_put_echo_skb(struct sk_buff *skb, struct net_device *dev,
 	if (idx >= priv->echo_skb_max) {
 		netdev_err(dev, "%s: BUG! Trying to access can_priv::echo_skb out of bounds (%u/max %u)\n",
 			   __func__, idx, priv->echo_skb_max);
+		dev_kfree_skb_any(skb);
 		return -EINVAL;
 	}
 
-- 
2.53.0

[PATCH net-next 06/11] can: isotp: check the frame type, not just the length

[Marc Kleine-Budde]

From: Kaixuan Li <kaixuanli0131@gmail.com>

isotp_rcv() separates Classic CAN from CAN FD by skb->len alone:

	if (skb->len != so->ll.mtu)
		return;

	cf = (struct canfd_frame *)skb->data;

A CAN XL frame with cxl->len 4 is CAN_MTU bytes, so it passes, and is then
read as a canfd_frame whose len comes out of canxl_frame.flags: at least
0x80.

Of the paths that follow, only the flow control one uses that length
without bounding it first, so check_pad() walks to 255 over a 16-byte
frame and the caller reports EBADMSG on an unrelated socket.

bcm_rx_handler(), j1939_can_recv(), can_can_gw_rcv() and raw_rcv() check
the frame type here, and can_dropped_invalid_skb() switches on
skb->protocol on the transmit side. isotp_rcv() is the gap.

Fixes: fb08cba12b52 ("can: canxl: update CAN infrastructure for CAN XL frames")
Signed-off-by: Kaixuan Li <kaixuanli0131@gmail.com>
Reviewed-by: Oliver Hartkopp <socketcan@hartkopp.net>
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Reviewed-by: Quchaosheng <quchaosheng000406@163.com>
Link: https://patch.msgid.link/20260920035626.2581040-1-kaixuanli0131@gmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 net/can/isotp.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/can/isotp.c b/net/can/isotp.c
index f5dc9d04bd68..d3e43ab48425 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -755,6 +755,14 @@ static void isotp_rcv(struct sk_buff *skb, void *data)
 	if (skb->len != so->ll.mtu)
 		return;
 
+	/* check for correct CAN CC/FD frame content */
+	if (so->ll.mtu == CAN_MTU) {
+		if (!can_is_can_skb(skb))
+			return;
+	} else if (!can_is_canfd_skb(skb)) {
+		return;
+	}
+
 	cf = (struct canfd_frame *)skb->data;
 
 	/* if enabled: check reception of my configured extended address */
-- 
2.53.0

[PATCH net-next 07/11] can: proc: reset pkg_stats atomics individually

[Marc Kleine-Budde]

From: Runyu Xiao <runyu.xiao@seu.edu.cn>

Commit 80b5f90158d1 ("can: statistics: use atomic access in hot path")
converted several members of struct can_pkg_stats to atomic_long_t and
updated the hot TX/RX and procfs read paths to use atomic_long_*()
helpers. However, can_init_stats() still clears the whole struct with
memset().

can_init_stats() is reached from can_stat_update() in timer context and
also from the procfs reset path. Those paths can run while the TX/RX hot
paths are concurrently updating rx_frames, tx_frames, matches and their
*_delta counters. Hitting the whole-struct memset() in that window
performs plain writes to fields that otherwise follow an atomic_long_t
access contract, which can lose or mix live statistics updates.

This issue was found by source-level API-misuse analysis looking for
whole-object resets left behind after atomic_long_t conversions, then
manually audited on Linux v6.18.21.

Replace the whole-struct memset() with a helper that resets the
atomic_long_t counters via atomic_long_set() and clears the derived
scalar statistics explicitly. This preserves the existing reset
semantics for scalar fields while restoring atomic access discipline for
the live counters.

Build-tested by compiling net/can/proc.o on x86_64 netdev/main.
Runtime-tested with a QEMU + vcan setup on Linux v6.18.21 by driving
concurrent traffic and reset_stats reads, which reproduced inconsistent
exported statistics before the fix.

[Hartkopp] can_stat_update() also read the *_delta counters at the
beginning and cleared them with atomic_long_set() at the end. Increments
from the hot path in between were lost for both the current and the next
interval. Use atomic_long_xchg() to fetch and clear the *_delta counters
in one atomic step instead.

Fixes: 80b5f90158d1 ("can: statistics: use atomic access in hot path")
Cc: stable@vger.kernel.org
Signed-off-by: Runyu Xiao <runyu.xiao@seu.edu.cn>
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://patch.msgid.link/20261019152741.54854-2-socketcan@hartkopp.net
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 net/can/proc.c | 39 +++++++++++++++++++++++++++++----------
 1 file changed, 29 insertions(+), 10 deletions(-)

diff --git a/net/can/proc.c b/net/can/proc.c
index de4d05ae3459..70104f13077e 100644
--- a/net/can/proc.c
+++ b/net/can/proc.c
@@ -76,16 +76,39 @@ static const char rx_list_name[][8] = {
  * af_can statistics stuff
  */
 
+static void can_reset_pkg_stats(struct can_pkg_stats *pkg_stats)
+{
+	atomic_long_set(&pkg_stats->rx_frames, 0);
+	atomic_long_set(&pkg_stats->tx_frames, 0);
+	atomic_long_set(&pkg_stats->matches, 0);
+
+	pkg_stats->total_rx_rate = 0;
+	pkg_stats->total_tx_rate = 0;
+	pkg_stats->total_rx_match_ratio = 0;
+
+	pkg_stats->current_rx_rate = 0;
+	pkg_stats->current_tx_rate = 0;
+	pkg_stats->current_rx_match_ratio = 0;
+
+	pkg_stats->max_rx_rate = 0;
+	pkg_stats->max_tx_rate = 0;
+	pkg_stats->max_rx_match_ratio = 0;
+
+	atomic_long_set(&pkg_stats->rx_frames_delta, 0);
+	atomic_long_set(&pkg_stats->tx_frames_delta, 0);
+	atomic_long_set(&pkg_stats->matches_delta, 0);
+}
+
 static void can_init_stats(struct net *net)
 {
 	struct can_pkg_stats *pkg_stats = net->can.pkg_stats;
 	struct can_rcv_lists_stats *rcv_lists_stats = net->can.rcv_lists_stats;
 	/*
-	 * This memset function is called from a timer context (when
+	 * This stats reset is called from a timer context (when
 	 * can_stattimer is active which is the default) OR in a process
 	 * context (reading the proc_fs when can_stattimer is disabled).
 	 */
-	memset(pkg_stats, 0, sizeof(struct can_pkg_stats));
+	can_reset_pkg_stats(pkg_stats);
 	pkg_stats->jiffies_init = jiffies;
 
 	rcv_lists_stats->stats_reset++;
@@ -121,9 +144,10 @@ void can_stat_update(struct timer_list *t)
 	long rx_frames = atomic_long_read(&pkg_stats->rx_frames);
 	long tx_frames = atomic_long_read(&pkg_stats->tx_frames);
 	long matches = atomic_long_read(&pkg_stats->matches);
-	long rx_frames_delta = atomic_long_read(&pkg_stats->rx_frames_delta);
-	long tx_frames_delta = atomic_long_read(&pkg_stats->tx_frames_delta);
-	long matches_delta = atomic_long_read(&pkg_stats->matches_delta);
+	/* fetch and clear values for 'current rate' calculation */
+	long rx_frames_delta = atomic_long_xchg(&pkg_stats->rx_frames_delta, 0);
+	long tx_frames_delta = atomic_long_xchg(&pkg_stats->tx_frames_delta, 0);
+	long matches_delta = atomic_long_xchg(&pkg_stats->matches_delta, 0);
 
 	/* restart counting in timer context on user request */
 	if (user_reset)
@@ -172,11 +196,6 @@ void can_stat_update(struct timer_list *t)
 	if (pkg_stats->max_rx_match_ratio < pkg_stats->current_rx_match_ratio)
 		pkg_stats->max_rx_match_ratio = pkg_stats->current_rx_match_ratio;
 
-	/* clear values for 'current rate' calculation */
-	atomic_long_set(&pkg_stats->tx_frames_delta, 0);
-	atomic_long_set(&pkg_stats->rx_frames_delta, 0);
-	atomic_long_set(&pkg_stats->matches_delta, 0);
-
 	/* restart timer (one second) */
 	mod_timer(&net->can.stattimer, round_jiffies(jiffies + HZ));
 }
-- 
2.53.0

[PATCH net-next 08/11] can: proc: skip stats calculation after reset in can_stat_update()

[Marc Kleine-Budde]

From: Oliver Hartkopp <socketcan@hartkopp.net>

Commit 80b5f90158d1 ("can: statistics: use atomic access in hot path")
introduced local snapshots of the statistics counters at the beginning
of can_stat_update(). When can_init_stats() resets the statistics, these
stale pre-reset snapshots are still used for the following total/current
/max calculations and overwrite the freshly reset values. Additionally a
jiffies tick between the snapshot and the reset could trigger a second
can_init_stats() call.

Merge the reset conditions into a single check and skip the calculation
for the current interval when the statistics have been reset.

Fixes: 80b5f90158d1 ("can: statistics: use atomic access in hot path")
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://patch.msgid.link/20261019152741.54854-3-socketcan@hartkopp.net
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 net/can/proc.c | 30 ++++++++++++------------------
 1 file changed, 12 insertions(+), 18 deletions(-)

diff --git a/net/can/proc.c b/net/can/proc.c
index 70104f13077e..fb144d2adc35 100644
--- a/net/can/proc.c
+++ b/net/can/proc.c
@@ -149,25 +149,18 @@ void can_stat_update(struct timer_list *t)
 	long tx_frames_delta = atomic_long_xchg(&pkg_stats->tx_frames_delta, 0);
 	long matches_delta = atomic_long_xchg(&pkg_stats->matches_delta, 0);
 
-	/* restart counting in timer context on user request */
-	if (user_reset)
-		can_init_stats(net);
-
-	/* restart counting on jiffies overflow */
-	if (j < pkg_stats->jiffies_init)
-		can_init_stats(net);
-
-	/* prevent overflow in calc_rate() */
-	if (rx_frames > (LONG_MAX / HZ))
-		can_init_stats(net);
-
-	/* prevent overflow in calc_rate() */
-	if (tx_frames > (LONG_MAX / HZ))
-		can_init_stats(net);
-
-	/* matches overflow - very improbable */
-	if (matches > (LONG_MAX / 100))
+	/*
+	 * Restart counting in timer context on user request, on jiffies
+	 * overflow or to prevent overflows in calc_rate() and in the
+	 * match ratio calculation. The local snapshots are stale after
+	 * the reset, so skip the calculation for this interval.
+	 */
+	if (user_reset || j < pkg_stats->jiffies_init ||
+	    rx_frames > (LONG_MAX / HZ) || tx_frames > (LONG_MAX / HZ) ||
+	    matches > (LONG_MAX / 100)) {
 		can_init_stats(net);
+		goto out;
+	}
 
 	/* calc total values */
 	if (rx_frames)
@@ -196,6 +189,7 @@ void can_stat_update(struct timer_list *t)
 	if (pkg_stats->max_rx_match_ratio < pkg_stats->current_rx_match_ratio)
 		pkg_stats->max_rx_match_ratio = pkg_stats->current_rx_match_ratio;
 
+out:
 	/* restart timer (one second) */
 	mod_timer(&net->can.stattimer, round_jiffies(jiffies + HZ));
 }
-- 
2.53.0

[PATCH net-next 09/11] can: proc: remove pointers from CAN specific proc output

[Marc Kleine-Budde]

From: Oliver Hartkopp <socketcan@hartkopp.net>

The proc content in /proc/net/can/ and /proc/net/can-bcm/ is intended to
check the internal filter lists (af_can, can_raw) and the efficiency and
functionality of can_bcm jobs. While exposing kernel addresses was
acceptable when this code was written the times have changed and multiple
attempts have been made to hash or remove such now sensitive data.

This patch removes the disclosure of pointers and instead provides the
function names and sock inode numbers when available. When the function
name can not be resolved (e.g. KALLSYMS=n or stripped module symbols)
%ps would fall back to the raw text address. Therefore (unknown) is
printed instead in this case. As there's no known tooling around the CAN
specific proc output breaking the ABI with this rework creates no issue.

Suggested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://patch.msgid.link/20261019152741.54854-4-socketcan@hartkopp.net
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 Documentation/networking/can.rst | 16 ++++++++++------
 include/linux/can/core.h         |  2 +-
 net/can/af_can.c                 |  6 +++---
 net/can/af_can.h                 |  2 +-
 net/can/bcm.c                    | 14 +++++++-------
 net/can/gw.c                     |  2 +-
 net/can/isotp.c                  |  4 ++--
 net/can/j1939/main.c             |  2 +-
 net/can/proc.c                   | 26 ++++++++++++++++----------
 net/can/raw.c                    |  4 ++--
 10 files changed, 44 insertions(+), 34 deletions(-)

diff --git a/Documentation/networking/can.rst b/Documentation/networking/can.rst
index 536ff411da1d..51bc70748f75 100644
--- a/Documentation/networking/can.rst
+++ b/Documentation/networking/can.rst
@@ -1040,17 +1040,21 @@ As described in :ref:`socketcan-receive-lists` the SocketCAN core uses several f
 lists to deliver received CAN frames to CAN protocol modules. These
 receive lists, their filters and the count of filter matches can be
 checked in the appropriate receive list. All entries contain the
-device and a protocol module identifier::
+CAN network device, the filter (can_id/can_mask), the number of filter
+matches, the inode number of the subscribing socket and the name of the
+receive function. A sock_inode of 0 denotes a kernel internal subscriber
+without a socket (e.g. CAN gateway or J1939). When the function name can
+not be resolved (e.g. with CONFIG_KALLSYMS=n) "(unknown)" is printed::
 
     foo@bar:~$ cat /proc/net/can/rcvlist_all
 
     receive list 'rx_all':
-      (vcan3: no entry)
-      (vcan2: no entry)
-      (vcan1: no entry)
-      device   can_id   can_mask  function  userdata   matches  ident
-       vcan0     000    00000000  f88e6370  f6c6f400         0  raw
       (any: no entry)
+      device   can_id   can_mask   matches  sock_inode  function
+       vcan0     000    00000000         0       63586  raw_rcv [can_raw]
+      (vcan1: no entry)
+      (vcan2: no entry)
+      (vcan3: no entry)
 
 In this example an application requests any CAN traffic from vcan0::
 
diff --git a/include/linux/can/core.h b/include/linux/can/core.h
index 2de74c2b78b6..effb5c31ef40 100644
--- a/include/linux/can/core.h
+++ b/include/linux/can/core.h
@@ -51,7 +51,7 @@ extern void can_proto_unregister(const struct can_proto *cp);
 int can_rx_register(struct net *net, struct net_device *dev,
 		    canid_t can_id, canid_t mask,
 		    void (*func)(struct sk_buff *, void *),
-		    void *data, char *ident, struct sock *sk);
+		    void *data, u64 ino, struct sock *sk);
 
 extern void can_rx_unregister(struct net *net, struct net_device *dev,
 			      canid_t can_id, canid_t mask,
diff --git a/net/can/af_can.c b/net/can/af_can.c
index 34fe3b28d576..6ebe9d3689ac 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -418,7 +418,7 @@ static struct hlist_head *can_rcv_list_find(canid_t *can_id, canid_t *mask,
  * @mask: CAN mask (see description)
  * @func: callback function on filter match
  * @data: returned parameter for callback function
- * @ident: string for calling module identification
+ * @ino: inode number of sock (0 = unknown)
  * @sk: socket pointer (might be NULL)
  *
  * Description:
@@ -443,7 +443,7 @@ static struct hlist_head *can_rcv_list_find(canid_t *can_id, canid_t *mask,
  */
 int can_rx_register(struct net *net, struct net_device *dev, canid_t can_id,
 		    canid_t mask, void (*func)(struct sk_buff *, void *),
-		    void *data, char *ident, struct sock *sk)
+		    void *data, u64 ino, struct sock *sk)
 {
 	struct receiver *rcv;
 	struct hlist_head *rcv_list;
@@ -472,7 +472,7 @@ int can_rx_register(struct net *net, struct net_device *dev, canid_t can_id,
 	atomic_long_set(&rcv->matches, 0);
 	rcv->func = func;
 	rcv->data = data;
-	rcv->ident = ident;
+	rcv->ino = ino;
 	rcv->sk = sk;
 
 	hlist_add_head_rcu(&rcv->list, rcv_list);
diff --git a/net/can/af_can.h b/net/can/af_can.h
index 87887014f562..6e593ed5db5f 100644
--- a/net/can/af_can.h
+++ b/net/can/af_can.h
@@ -55,7 +55,7 @@ struct receiver {
 	atomic_long_t matches;
 	void (*func)(struct sk_buff *skb, void *data);
 	void *data;
-	char *ident;
+	u64 ino;
 	struct sock *sk;
 	struct rcu_head rcu;
 };
diff --git a/net/can/bcm.c b/net/can/bcm.c
index 3d637a1e0ac1..6c85a76477c3 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -220,9 +220,7 @@ static int bcm_proc_show(struct seq_file *m, void *v)
 	struct bcm_sock *bo = bcm_sk(sk);
 	struct bcm_op *op;
 
-	seq_printf(m, ">>> socket %pK", sk->sk_socket);
-	seq_printf(m, " / sk %pK", sk);
-	seq_printf(m, " / bo %pK", bo);
+	seq_printf(m, ">>> sock inode %s", bo->procname);
 	seq_printf(m, " / dropped %lu", bo->dropped_usr_msgs);
 	seq_printf(m, " / bound %s", bcm_proc_getifname(net, ifname, bo->ifindex));
 	seq_printf(m, " <<<\n");
@@ -1536,7 +1534,7 @@ 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);
+						      sock_i_ino(sk), sk);
 
 				/* keep a tracked reference so that a later
 				 * unregister can safely reach the device even
@@ -1560,7 +1558,8 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
 		} else {
 			err = can_rx_register(sock_net(sk), NULL, op->can_id,
 					      REGMASK(op->can_id),
-					      bcm_rx_handler, op, "bcm", sk);
+					      bcm_rx_handler, op,
+					      sock_i_ino(sk), sk);
 		}
 
 		if (err) {
@@ -2040,8 +2039,9 @@ static int bcm_connect(struct socket *sock, struct sockaddr_unsized *uaddr, int
 
 #if IS_ENABLED(CONFIG_PROC_FS)
 	if (net->can.bcmproc_dir) {
-		/* unique socket address as filename */
-		sprintf(bo->procname, "%llu", sock_i_ino(sk));
+		/* use unique socket inode number as filename */
+		snprintf(bo->procname, sizeof(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);
diff --git a/net/can/gw.c b/net/can/gw.c
index 5793cb2420ed..36f9aa0f7026 100644
--- a/net/can/gw.c
+++ b/net/can/gw.c
@@ -579,7 +579,7 @@ static inline int cgw_register_filter(struct net *net, struct cgw_job *gwj)
 {
 	return can_rx_register(net, gwj->src.dev, gwj->ccgw.filter.can_id,
 			       gwj->ccgw.filter.can_mask, can_can_gw_rcv,
-			       gwj, "gw", NULL);
+			       gwj, 0, NULL);
 }
 
 static inline void cgw_unregister_filter(struct net *net, struct cgw_job *gwj)
diff --git a/net/can/isotp.c b/net/can/isotp.c
index d3e43ab48425..64ff203a37f4 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -1633,14 +1633,14 @@ static int isotp_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int l
 
 	if (isotp_register_rxid(so))
 		can_rx_register(net, dev, rx_id, SINGLE_MASK(rx_id),
-				isotp_rcv, sk, "isotp", sk);
+				isotp_rcv, sk, sock_i_ino(sk), sk);
 
 	/* no consecutive frame echo skb in flight */
 	WRITE_ONCE(so->cfecho, 0);
 
 	/* register for echo skb's */
 	can_rx_register(net, dev, tx_id, SINGLE_MASK(tx_id),
-			isotp_rcv_echo, sk, "isotpe", sk);
+			isotp_rcv_echo, sk, sock_i_ino(sk), sk);
 
 	/* switch to new settings */
 	so->ifindex = ifindex;
diff --git a/net/can/j1939/main.c b/net/can/j1939/main.c
index 5e5e6c228f22..d9384cf0e356 100644
--- a/net/can/j1939/main.c
+++ b/net/can/j1939/main.c
@@ -184,7 +184,7 @@ static int j1939_can_rx_register(struct j1939_priv *priv)
 
 	j1939_priv_get(priv);
 	ret = can_rx_register(dev_net(ndev), ndev, J1939_CAN_ID, J1939_CAN_MASK,
-			      j1939_can_recv, priv, "j1939", NULL);
+			      j1939_can_recv, priv, 0, NULL);
 	if (ret < 0) {
 		j1939_priv_put(priv);
 		return ret;
diff --git a/net/can/proc.c b/net/can/proc.c
index fb144d2adc35..b7496d2a37cd 100644
--- a/net/can/proc.c
+++ b/net/can/proc.c
@@ -204,26 +204,32 @@ static void can_print_rcvlist(struct seq_file *m, struct hlist_head *rx_list,
 	struct receiver *r;
 
 	hlist_for_each_entry_rcu(r, rx_list, list) {
+		char symcheck[4];
 		char *fmt = (r->can_id & CAN_EFF_FLAG)?
-			"   %-5s  %08x  %08x  %pK  %pK  %8ld  %s\n" :
-			"   %-5s     %03x    %08x  %pK  %pK  %8ld  %s\n";
+			"  %6s  %08x  %08x  %8ld  %10llu" :
+			"  %6s     %03x    %08x  %8ld  %10llu";
 
 		seq_printf(m, fmt, DNAME(dev), r->can_id, r->mask,
-			   r->func, r->data, atomic_long_read(&r->matches),
-			   r->ident);
+			   atomic_long_read(&r->matches), r->ino);
+
+		/* %ps falls back to the raw text address when the symbol
+		 * can not be resolved (KALLSYMS=n, stripped module symbols)
+		 */
+		snprintf(symcheck, sizeof(symcheck), "%ps", r->func);
+		if (strncmp(symcheck, "0x", 2))
+			seq_printf(m, "  %ps\n", r->func);
+		else
+			seq_puts(m, "  (unknown)\n");
 	}
 }
 
 static void can_print_recv_banner(struct seq_file *m)
 {
 	/*
-	 *                  can1.  00000000  00000000  00000000
-	 *                 .......          0  tp20
+	 *    device   can_id   can_mask   matches  sock_inode  function
+	 *     vcan0     000    00000000         0       43798  raw_rcv [can_raw]
 	 */
-	if (IS_ENABLED(CONFIG_64BIT))
-		seq_puts(m, "  device   can_id   can_mask      function          userdata       matches  ident\n");
-	else
-		seq_puts(m, "  device   can_id   can_mask  function  userdata   matches  ident\n");
+	seq_puts(m, "  device   can_id   can_mask   matches  sock_inode  function\n");
 }
 
 static int can_stats_proc_show(struct seq_file *m, void *v)
diff --git a/net/can/raw.c b/net/can/raw.c
index 6944ebab3feb..3e57f72a3afe 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -226,7 +226,7 @@ static int raw_enable_filters(struct net *net, struct net_device *dev,
 	for (i = 0; i < count; i++) {
 		err = can_rx_register(net, dev, filter[i].can_id,
 				      filter[i].can_mask,
-				      raw_rcv, sk, "raw", sk);
+				      raw_rcv, sk, sock_i_ino(sk), sk);
 		if (err) {
 			/* clean up successfully registered filters */
 			while (--i >= 0)
@@ -247,7 +247,7 @@ static int raw_enable_errfilter(struct net *net, struct net_device *dev,
 
 	if (err_mask)
 		err = can_rx_register(net, dev, 0, err_mask | CAN_ERR_FLAG,
-				      raw_rcv, sk, "raw", sk);
+				      raw_rcv, sk, sock_i_ino(sk), sk);
 
 	return err;
 }
-- 
2.53.0

[PATCH net-next 10/11] can: replace ARPHRD_CAN type checks with can_get_ml_priv()

[Marc Kleine-Budde]

From: Oliver Hartkopp <socketcan@hartkopp.net>

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. A valid pointer
returned by can_get_ml_priv() therefore identifies a real CAN device.

The referenced commit only converted the j1939 and proc code to this
check, while the other parts of the CAN subsystem still rely on
dev->type == ARPHRD_CAN.

The TUNSETLINK ioctl allows a down TUN/TAP device to set its hardware
type to ARPHRD_CAN while dev->ml_priv remains NULL. Such a repurposed
netdevice passes the ARPHRD_CAN checks and triggers a NULL pointer
dereference when CAN filters are created and when they are removed,
e.g. by the CAN protocols' netdevice notifier handlers. This only
requires owning a TUN/TAP device or CAP_NET_ADMIN in an unprivileged
user namespace.

Convert the remaining ARPHRD_CAN checks in af_can, bcm, gw, isotp and
raw 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>
Link: https://patch.msgid.link/20261012164802.94113-1-socketcan@hartkopp.net
Link: https://patch.msgid.link/20261019152741.54854-5-socketcan@hartkopp.net
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 net/can/af_can.c | 15 ++++++---------
 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(+), 19 deletions(-)

diff --git a/net/can/af_can.c b/net/can/af_can.c
index 6ebe9d3689ac..d97f85fc3232 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -226,7 +226,7 @@ int can_send(struct sk_buff *skb, int loop)
 		goto inval_skb;
 	}
 
-	if (unlikely(skb->dev->type != ARPHRD_CAN)) {
+	if (unlikely(!can_get_ml_priv(skb->dev))) {
 		err = -EPERM;
 		goto inval_skb;
 	}
@@ -452,7 +452,7 @@ int can_rx_register(struct net *net, struct net_device *dev, canid_t can_id,
 
 	/* 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)))
@@ -519,7 +519,7 @@ void can_rx_unregister(struct net *net, struct net_device *dev, canid_t can_id,
 	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)))
@@ -684,8 +684,7 @@ static int can_rcv(struct sk_buff *skb, struct net_device *dev,
 {
 	struct can_skb_ext *csx = can_skb_ext_find(skb);
 
-	if (unlikely(dev->type != ARPHRD_CAN || !can_get_ml_priv(dev) ||
-		     !csx || !can_is_can_skb(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);
 
@@ -710,8 +709,7 @@ static int canfd_rcv(struct sk_buff *skb, struct net_device *dev,
 {
 	struct can_skb_ext *csx = can_skb_ext_find(skb);
 
-	if (unlikely(dev->type != ARPHRD_CAN || !can_get_ml_priv(dev) ||
-		     !csx || !can_is_canfd_skb(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);
 
@@ -736,8 +734,7 @@ static int canxl_rcv(struct sk_buff *skb, struct net_device *dev,
 {
 	struct can_skb_ext *csx = can_skb_ext_find(skb);
 
-	if (unlikely(dev->type != ARPHRD_CAN || !can_get_ml_priv(dev) ||
-		     !csx || !can_is_canxl_skb(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);
 
diff --git a/net/can/bcm.c b/net/can/bcm.c
index 6c85a76477c3..6759662e024c 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -54,6 +54,7 @@
 #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>
@@ -1718,7 +1719,7 @@ static int bcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
 				goto out_release;
 			}
 
-			if (dev->type != ARPHRD_CAN) {
+			if (!can_get_ml_priv(dev)) {
 				dev_put(dev);
 				ret = -ENODEV;
 				goto out_release;
@@ -1866,7 +1867,7 @@ static int bcm_notifier(struct notifier_block *nb, unsigned long msg,
 {
 	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;
@@ -2023,7 +2024,7 @@ static int bcm_connect(struct socket *sock, struct sockaddr_unsized *uaddr, int
 			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 36f9aa0f7026..8a5327d8a00e 100644
--- a/net/can/gw.c
+++ b/net/can/gw.c
@@ -52,6 +52,7 @@
 #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>
@@ -612,7 +613,7 @@ static int cgw_notifier(struct notifier_block *nb,
 	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) {
@@ -1163,7 +1164,7 @@ static int cgw_create_job(struct sk_buff *skb,  struct nlmsghdr *nlh,
 	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);
@@ -1171,7 +1172,7 @@ static int cgw_create_job(struct sk_buff *skb,  struct nlmsghdr *nlh,
 	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? */
diff --git a/net/can/isotp.c b/net/can/isotp.c
index 64ff203a37f4..5e1c3971ebfc 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -65,6 +65,7 @@
 #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>
@@ -1618,7 +1619,7 @@ static int isotp_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int l
 		err = -ENODEV;
 		goto out;
 	}
-	if (dev->type != ARPHRD_CAN) {
+	if (!can_get_ml_priv(dev)) {
 		err = -ENODEV;
 		goto out_put_dev;
 	}
@@ -1905,7 +1906,7 @@ static int isotp_notifier(struct notifier_block *nb, unsigned long msg,
 {
 	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;
diff --git a/net/can/raw.c b/net/can/raw.c
index 3e57f72a3afe..dfea48768b23 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -348,7 +348,7 @@ static int raw_notifier(struct notifier_block *nb, unsigned long msg,
 {
 	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;
@@ -491,7 +491,7 @@ static int raw_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int len
 			err = -ENODEV;
 			goto out;
 		}
-		if (dev->type != ARPHRD_CAN) {
+		if (!can_get_ml_priv(dev)) {
 			err = -ENODEV;
 			goto out_put_dev;
 		}
-- 
2.53.0

Re: [PATCH net-next 10/11] can: replace ARPHRD_CAN type checks with can_get_ml_priv()

[netdev-bot+sashiko]

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 is inaccurate about where the crash happens.

Pre-existing issues:
- [Medium] This problem wasn't introduced by this patch, but isotp_bind()
  in net/can/isotp.c still ignores the return value of both…

--

can: replace ARPHRD_CAN type checks with can_get_ml_priv()

This patch replaces the remaining dev->type == ARPHRD_CAN checks in
af_can, bcm, gw, isotp and raw with can_get_ml_priv(). The TUNSETLINK
ioctl can switch a TUN/TAP device to ARPHRD_CAN while dev->ml_priv stays
NULL, and such a device passes the old type checks.

Link: https://patch.msgid.link/20261012164802.94113-1-socketcan@hartkopp.net
Link: https://patch.msgid.link/20261019152741.54854-5-socketcan@hartkopp.net

> The TUNSETLINK ioctl allows a down TUN/TAP device to set its hardware
> type to ARPHRD_CAN while dev->ml_priv remains NULL. Such a repurposed
> netdevice passes the ARPHRD_CAN checks and triggers a NULL pointer
> dereference when CAN filters are created and when they are removed,
> e.g. by the CAN protocols' netdevice notifier handlers.

[Severity: Low]
Is the "when CAN filters are created" part accurate for this tree?

Commit 8aa59e3559494 ("can: af_can: fix NULL pointer dereference in
can_rx_register()") already made can_rx_register() reject devices
without ml_priv:

    if (dev && (dev->type != ARPHRD_CAN || !can_get_ml_priv(dev)))
        return -ENODEV;

raw, bcm, gw (through cgw_register_filter()) and isotp all create filters
through can_rx_register(). So creating a filter can't reach the NULL
ml_priv.

The only dereference left seems to be on removal. can_rx_unregister()
checked only dev->type, and then can_dev_rcv_lists_find() does:

    struct can_ml_priv *can_ml = can_get_ml_priv(dev);
    return &can_ml->dev_rcv_lists;

The spin_lock_bh() on dev_rcv_lists->lock then goes through a near-NULL
pointer.

The path that actually gets there looks like isotp. isotp_bind() ignores
the -ENODEV from both can_rx_register() calls and sets so->bound = 1
anyway. Later, unregistering the filters crashes:

isotp_bind()
    can_rx_register() -> -ENODEV, ignored
    so->bound = 1

isotp_release() or isotp_notify(NETDEV_UNREGISTER)
    can_rx_unregister()
        can_dev_rcv_lists_find()
        spin_lock_bh(&dev_rcv_lists->lock)

The code change itself looks correct. Could the commit message describe
the crash on removal and the isotp path instead? That would show stable
backporters which code is affected.

> diff --git a/net/can/isotp.c b/net/can/isotp.c
> index 64ff203a37f4..5e1c3971ebfc 100644
> --- a/net/can/isotp.c
> +++ b/net/can/isotp.c

[ ... ]

> @@ -1618,7 +1619,7 @@ static int isotp_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int l
>  		err = -ENODEV;
>  		goto out;
>  	}
> -	if (dev->type != ARPHRD_CAN) {
> +	if (!can_get_ml_priv(dev)) {
>  		err = -ENODEV;
>  		goto out_put_dev;
>  	}

[Severity: Medium]
This is a pre-existing issue and was not introduced by this patch.
Further down in isotp_bind(), the return values of both can_rx_register()
calls are still ignored:

	if (isotp_register_rxid(so))
		can_rx_register(net, dev, rx_id, SINGLE_MASK(rx_id),
				isotp_rcv, sk, sock_i_ino(sk), sk);
	...
	can_rx_register(net, dev, tx_id, SINGLE_MASK(tx_id),
			isotp_rcv_echo, sk, sock_i_ino(sk), sk);

	/* switch to new settings */
	...
	so->bound = 1;

The new can_get_ml_priv() check rules out the -ENODEV cases. However,
can_rx_register() can still return -ENOMEM:

	rcv = kmem_cache_alloc(rcv_cache, GFP_KERNEL);
	if (!rcv)
		return -ENOMEM;

In that case, does bind() report success even though the socket has no RX
receiver, no echo receiver, or neither? RX frames would be dropped without
any error, and isotp TX would wait for echo frames that never arrive.

A later isotp_release() or isotp_notify() for NETDEV_UNREGISTER would
only print "receive list entry not found" from can_rx_unregister(). It
would not crash.

Other CAN protocols handle this: raw_enable_filters() rolls back on error,
and bcm_rx_setup() checks err. Should isotp_bind() check these results and
unwind too? The last patch in this series ("can: protect the receive lists
with a per-device lock") still leaves both calls unchecked.

-- 
Sashiko AI review · https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20261019170834.1727150-2-mkl%40pengutronix.de

Re: [PATCH net-next 10/11] can: replace ARPHRD_CAN type checks with can_get_ml_priv()

[Oliver Hartkopp]

On 20.10.26 19:11, netdev-bot+sashiko@kernel.org wrote:
> 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 is inaccurate about where the crash happens.
> 
> Pre-existing issues:
> - [Medium] This problem wasn't introduced by this patch, but isotp_bind()
>    in net/can/isotp.c still ignores the return value of both…
> 
> --
> 
> can: replace ARPHRD_CAN type checks with can_get_ml_priv()
> 
> This patch replaces the remaining dev->type == ARPHRD_CAN checks in
> af_can, bcm, gw, isotp and raw with can_get_ml_priv(). The TUNSETLINK
> ioctl can switch a TUN/TAP device to ARPHRD_CAN while dev->ml_priv stays
> NULL, and such a device passes the old type checks.
> 
> Link: https://patch.msgid.link/20261012164802.94113-1-socketcan@hartkopp.net
> Link: https://patch.msgid.link/20261019152741.54854-5-socketcan@hartkopp.net
> 
>> The TUNSETLINK ioctl allows a down TUN/TAP device to set its hardware
>> type to ARPHRD_CAN while dev->ml_priv remains NULL. Such a repurposed
>> netdevice passes the ARPHRD_CAN checks and triggers a NULL pointer
>> dereference when CAN filters are created and when they are removed,
>> e.g. by the CAN protocols' netdevice notifier handlers.
> 
> [Severity: Low]
> Is the "when CAN filters are created" part accurate for this tree?
> 
> Commit 8aa59e3559494 ("can: af_can: fix NULL pointer dereference in
> can_rx_register()") already made can_rx_register() reject devices
> without ml_priv:
> 
>      if (dev && (dev->type != ARPHRD_CAN || !can_get_ml_priv(dev)))
>          return -ENODEV;

The commit message refers to the CAN filter register/unregister
procedure as a whole, not to a single code path in a specific tree.

Commit 8aa59e3559494 only added the ml_priv check to can_rx_register().
can_rx_unregister() and the CAN protocols kept checking dev->type only.
So that commit fixed the problem only partially, and the NULL pointer
dereference is still reachable on the unregister side.

This patch completes that fix. It uses can_get_ml_priv() as the only
criterion for a real CAN device in all register/unregister paths and in
the protocols' bind/notifier code. It no longer relies on each caller
handling the can_rx_register() return value correctly.

> 
> raw, bcm, gw (through cgw_register_filter()) and isotp all create filters
> through can_rx_register(). So creating a filter can't reach the NULL
> ml_priv.
> 
> The only dereference left seems to be on removal. can_rx_unregister()
> checked only dev->type, and then can_dev_rcv_lists_find() does:
> 
>      struct can_ml_priv *can_ml = can_get_ml_priv(dev);
>      return &can_ml->dev_rcv_lists;
> 
> The spin_lock_bh() on dev_rcv_lists->lock then goes through a near-NULL
> pointer.
> 
> The path that actually gets there looks like isotp. isotp_bind() ignores
> the -ENODEV from both can_rx_register() calls and sets so->bound = 1
> anyway. Later, unregistering the filters crashes:
> 
> isotp_bind()
>      can_rx_register() -> -ENODEV, ignored
>      so->bound = 1
> 
> isotp_release() or isotp_notify(NETDEV_UNREGISTER)
>      can_rx_unregister()
>          can_dev_rcv_lists_find()
>          spin_lock_bh(&dev_rcv_lists->lock)
> 
> The code change itself looks correct. Could the commit message describe
> the crash on removal and the isotp path instead? That would show stable
> backporters which code is affected.
> 
>> diff --git a/net/can/isotp.c b/net/can/isotp.c
>> index 64ff203a37f4..5e1c3971ebfc 100644
>> --- a/net/can/isotp.c
>> +++ b/net/can/isotp.c
> 
> [ ... ]
> 
>> @@ -1618,7 +1619,7 @@ static int isotp_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int l
>>   		err = -ENODEV;
>>   		goto out;
>>   	}
>> -	if (dev->type != ARPHRD_CAN) {
>> +	if (!can_get_ml_priv(dev)) {
>>   		err = -ENODEV;
>>   		goto out_put_dev;
>>   	}
> 
> [Severity: Medium]
> This is a pre-existing issue and was not introduced by this patch.
> Further down in isotp_bind(), the return values of both can_rx_register()
> calls are still ignored:

Right. That's a separate issue, and it doesn't belong to this patch. The
missing error handling in isotp_bind() will be addressed in a separate
patch.

Best regards,
Oliver

> 
> 	if (isotp_register_rxid(so))
> 		can_rx_register(net, dev, rx_id, SINGLE_MASK(rx_id),
> 				isotp_rcv, sk, sock_i_ino(sk), sk);
> 	...
> 	can_rx_register(net, dev, tx_id, SINGLE_MASK(tx_id),
> 			isotp_rcv_echo, sk, sock_i_ino(sk), sk);
> 
> 	/* switch to new settings */
> 	...
> 	so->bound = 1;
> 
> The new can_get_ml_priv() check rules out the -ENODEV cases. However,
> can_rx_register() can still return -ENOMEM:
> 
> 	rcv = kmem_cache_alloc(rcv_cache, GFP_KERNEL);
> 	if (!rcv)
> 		return -ENOMEM;
> 
> In that case, does bind() report success even though the socket has no RX
> receiver, no echo receiver, or neither? RX frames would be dropped without
> any error, and isotp TX would wait for echo frames that never arrive.
> 
> A later isotp_release() or isotp_notify() for NETDEV_UNREGISTER would
> only print "receive list entry not found" from can_rx_unregister(). It
> would not crash.
> 
> Other CAN protocols handle this: raw_enable_filters() rolls back on error,
> and bcm_rx_setup() checks err. Should isotp_bind() check these results and
> unwind too? The last patch in this series ("can: protect the receive lists
> with a per-device lock") still leaves both calls unchecked.
> 

[PATCH net-next 11/11] can: protect the receive lists with a per-device lock

[Marc Kleine-Budde]

From: Oliver Hartkopp <socketcan@hartkopp.net>

The receive lists of a CAN device are located in the device's
can_ml_priv and travel with the device when it is moved to another
network namespace. But they are protected by the per-netns
rcvlists_lock. So can_rx_unregister() needs dev_net(dev) to pick the
right lock and silently returns when the passed namespace does not
match dev_net(dev) anymore.

isotp_release() and bcm_release() leave their notifier list before they
take any lock that serializes against the netdev notifier, which runs
under RTNL. When the bound device is moved to another namespace in this
window, the notifier skips the socket and the release path has to remove
the filters itself. isotp_release() passes the socket's namespace, which
does not match dev_net(dev) anymore. bcm_rx_unreg() passes dev_net(dev),
which can_rx_unregister() reads again for its check, so a namespace
change between both reads makes the check fail as well. In both cases
can_rx_unregister() silently returns. As can_rx_register() stores
rcv->sk without a reference, the remaining receivers point to the freed
socket (isotp) or the freed op (bcm):

  BUG: KASAN: use-after-free in isotp_rcv+0x1570/0x24d0
  Read of size 1 at addr ffff888118130552 by task isotp_ns_uaf/578
   can_rcv_filter+0x4af/0x8c0
   can_receive+0x28d/0x3c0
   can_rcv+0x2a9/0x310
   __netif_receive_skb_one_core+0x21a/0x260
   process_backlog+0x210/0x760

Besides this, the lists of a device are protected by the rcvlists_lock
of the namespace that is passed in. Callers which pass dev_net(dev) read
it at different times, so the same lists may be modified under the locks
of different namespaces while the device is moved.

Taking RTNL in these release paths is no option: raw_bind(),
raw_setsockopt() and raw_release() already hold RTNL while adding and
removing up to CAN_RAW_FILTER_MAX filters per socket, which unprivileged
users can trigger repeatedly and which makes RTNL a global bottleneck.

Instead fix the root cause and add a spinlock to struct
can_dev_rcv_lists, which protects the receive lists of a CAN device or
the 'any' CAN device lists of a namespace. It is initialized in
can_set_ml_priv(), which is used by all CAN network devices. With this,
can_rx_unregister() finds the subscription independently of the
current namespace of the device. The protocols keep the device valid
with their tracked references. The per-netns rcvlists_lock only protects
the receive list statistics anymore, and the callers pass the namespace
that has been used for can_rx_register().

So isotp_release() and bcm_release() now remove their filters correctly
without RTNL, and raw_release(), raw_setsockopt(), raw_bind() and
isotp_bind() do not need RTNL anymore and add and remove their filters
under lock_sock(). To serialize bind() with NETDEV_UNREGISTER, bind()
publishes the device inside the RCU section of its lookup, and
raw_notify() and isotp_notify() recheck the bound device under lock_sock().

Fixes: 20bab8b88baa ("can: isotp: fix use-after-free race with concurrent NETDEV_UNREGISTER")
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
Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://patch.msgid.link/20261019152741.54854-6-socketcan@hartkopp.net
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 include/linux/can/can-ml.h |   3 +
 include/net/netns/can.h    |   2 +-
 net/can/af_can.c           |  40 +++++++----
 net/can/bcm.c              |  43 ++++-------
 net/can/isotp.c            |  40 +++++++----
 net/can/raw.c              | 142 ++++++++++++++++++++++++-------------
 6 files changed, 161 insertions(+), 109 deletions(-)

diff --git a/include/linux/can/can-ml.h b/include/linux/can/can-ml.h
index 1e99fda2b380..cfefa4a385be 100644
--- a/include/linux/can/can-ml.h
+++ b/include/linux/can/can-ml.h
@@ -45,6 +45,7 @@
 #include <linux/can.h>
 #include <linux/list.h>
 #include <linux/netdevice.h>
+#include <linux/spinlock.h>
 
 /* exposed CAN device capabilities for network layer */
 #define CAN_CAP_CC BIT(0) /* CAN CC aka Classical CAN */
@@ -59,6 +60,7 @@
 enum { RX_ERR, RX_ALL, RX_FIL, RX_INV, RX_MAX };
 
 struct can_dev_rcv_lists {
+	spinlock_t lock; /* protects the receive lists and entries */
 	struct hlist_head rx[RX_MAX];
 	struct hlist_head rx_sff[CAN_SFF_RCV_ARRAY_SZ];
 	struct hlist_head rx_eff[CAN_EFF_RCV_ARRAY_SZ];
@@ -81,6 +83,7 @@ static inline struct can_ml_priv *can_get_ml_priv(struct net_device *dev)
 static inline void can_set_ml_priv(struct net_device *dev,
 				   struct can_ml_priv *ml_priv)
 {
+	spin_lock_init(&ml_priv->dev_rcv_lists.lock);
 	netdev_set_ml_priv(dev, ml_priv, ML_PRIV_CAN);
 }
 
diff --git a/include/net/netns/can.h b/include/net/netns/can.h
index 48b79f7e6236..ef7aefdf7b23 100644
--- a/include/net/netns/can.h
+++ b/include/net/netns/can.h
@@ -29,7 +29,7 @@ struct netns_can {
 
 	/* receive filters subscribed for 'all' CAN devices */
 	struct can_dev_rcv_lists *rx_alldev_list;
-	spinlock_t rcvlists_lock;
+	spinlock_t rcvlists_lock; /* protects rcv_lists_stats */
 	struct timer_list stattimer; /* timer for statistics update */
 	struct can_pkg_stats *pkg_stats;
 	struct can_rcv_lists_stats *rcv_lists_stats;
diff --git a/net/can/af_can.c b/net/can/af_can.c
index d97f85fc3232..bf612c4b983d 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -462,9 +462,10 @@ int can_rx_register(struct net *net, struct net_device *dev, canid_t can_id,
 	if (!rcv)
 		return -ENOMEM;
 
-	spin_lock_bh(&net->can.rcvlists_lock);
-
 	dev_rcv_lists = can_dev_rcv_lists_find(net, dev);
+
+	spin_lock_bh(&dev_rcv_lists->lock);
+
 	rcv_list = can_rcv_list_find(&can_id, &mask, dev_rcv_lists);
 
 	rcv->can_id = can_id;
@@ -478,6 +479,9 @@ int can_rx_register(struct net *net, struct net_device *dev, canid_t can_id,
 	hlist_add_head_rcu(&rcv->list, rcv_list);
 	dev_rcv_lists->entries++;
 
+	spin_unlock_bh(&dev_rcv_lists->lock);
+
+	spin_lock_bh(&net->can.rcvlists_lock);
 	rcv_lists_stats->rcv_entries++;
 	rcv_lists_stats->rcv_entries_max = max(rcv_lists_stats->rcv_entries_max,
 					       rcv_lists_stats->rcv_entries);
@@ -509,6 +513,13 @@ static void can_rx_delete_receiver(struct rcu_head *rp)
  *
  * Description:
  *  Removes subscription entry depending on given (subscription) values.
+ *  The receive lists of a CAN device are protected by a per-device lock,
+ *  so the subscription is found even when the device has been moved to
+ *  another network namespace after can_rx_register(). The caller has to
+ *  ensure that @dev stays valid, e.g. by holding a reference to @dev or
+ *  RTNL. @net is the namespace that has been used for can_rx_register().
+ *  It selects the 'any' CAN device lists for @dev == NULL and is used for
+ *  the receive list statistics.
  */
 void can_rx_unregister(struct net *net, struct net_device *dev, canid_t can_id,
 		       canid_t mask, void (*func)(struct sk_buff *, void *),
@@ -522,12 +533,10 @@ void can_rx_unregister(struct net *net, struct net_device *dev, canid_t can_id,
 	if (dev && !can_get_ml_priv(dev))
 		return;
 
-	if (dev && !net_eq(net, dev_net(dev)))
-		return;
-
-	spin_lock_bh(&net->can.rcvlists_lock);
-
 	dev_rcv_lists = can_dev_rcv_lists_find(net, dev);
+
+	spin_lock_bh(&dev_rcv_lists->lock);
+
 	rcv_list = can_rcv_list_find(&can_id, &mask, dev_rcv_lists);
 
 	/* Search the receiver list for the item to delete.  This should
@@ -547,26 +556,26 @@ void can_rx_unregister(struct net *net, struct net_device *dev, canid_t can_id,
 	 * a warning here.
 	 */
 	if (!rcv) {
+		spin_unlock_bh(&dev_rcv_lists->lock);
 		pr_warn("can: receive list entry not found for dev %s, id %03X, mask %03X\n",
 			DNAME(dev), can_id, mask);
-		goto out;
+		return;
 	}
 
 	hlist_del_rcu(&rcv->list);
 	dev_rcv_lists->entries--;
 
+	spin_unlock_bh(&dev_rcv_lists->lock);
+
+	spin_lock_bh(&net->can.rcvlists_lock);
 	if (rcv_lists_stats->rcv_entries > 0)
 		rcv_lists_stats->rcv_entries--;
-
- out:
 	spin_unlock_bh(&net->can.rcvlists_lock);
 
 	/* schedule the receiver item for deletion */
-	if (rcv) {
-		if (rcv->sk)
-			sock_hold(rcv->sk);
-		call_rcu(&rcv->rcu, can_rx_delete_receiver);
-	}
+	if (rcv->sk)
+		sock_hold(rcv->sk);
+	call_rcu(&rcv->rcu, can_rx_delete_receiver);
 }
 EXPORT_SYMBOL(can_rx_unregister);
 
@@ -823,6 +832,7 @@ static int can_pernet_init(struct net *net)
 	net->can.rx_alldev_list = kzalloc_obj(*net->can.rx_alldev_list);
 	if (!net->can.rx_alldev_list)
 		goto out;
+	spin_lock_init(&net->can.rx_alldev_list->lock);
 	net->can.pkg_stats = kzalloc_obj(*net->can.pkg_stats);
 	if (!net->can.pkg_stats)
 		goto out_free_rx_alldev_list;
diff --git a/net/can/bcm.c b/net/can/bcm.c
index 6759662e024c..7bd2aa39777a 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -962,7 +962,7 @@ static void bcm_remove_op(struct bcm_op *op)
 static void bcm_rx_unreg(struct net_device *dev, struct bcm_op *op)
 {
 	if (op->rx_reg_dev == dev) {
-		can_rx_unregister(dev_net(dev), dev, op->can_id,
+		can_rx_unregister(sock_net(op->sk), dev, op->can_id,
 				  REGMASK(op->can_id), bcm_rx_handler, op);
 
 		/* mark as removed subscription */
@@ -988,21 +988,10 @@ static int bcm_delete_rx_op(struct list_head *ops, struct bcm_msg_head *mh,
 			/* disable automatic timer on frame reception */
 			op->flags |= RX_NO_AUTOTIMER;
 
-			/*
-			 * Don't care if we're bound or not (due to netdev
-			 * problems) can_rx_unregister() is always a save
-			 * thing to do here.
-			 */
 			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.
+				/* Only remove subscriptions that had not been
+				 * removed in bcm_notify(). op->rx_reg_dev keeps
+				 * the device's receive lists accessible.
 				 */
 				if (op->rx_reg_dev)
 					bcm_rx_unreg(op->rx_reg_dev, op);
@@ -1935,6 +1924,7 @@ static int bcm_release(struct socket *sock)
 	list_del(&bo->notifier);
 	spin_unlock(&bcm_notifier_lock);
 
+	/* bcm_notify() can not access this socket anymore */
 	lock_sock(sk);
 
 #if IS_ENABLED(CONFIG_PROC_FS)
@@ -1948,29 +1938,20 @@ static int bcm_release(struct socket *sock)
 		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.
-		 */
+	list_for_each_entry(op, &bo->rx_ops, list) {
 		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.
+			/* Only remove subscriptions that had not been removed
+			 * in bcm_notify(). op->rx_reg_dev keeps the device's
+			 * receive lists accessible.
 			 */
 			if (op->rx_reg_dev)
 				bcm_rx_unreg(op->rx_reg_dev, op);
-		} else
+		} else {
 			can_rx_unregister(net, NULL, op->can_id,
 					  REGMASK(op->can_id),
 					  bcm_rx_handler, op);
-
+		}
+		cond_resched();
 	}
 
 	synchronize_rcu();
diff --git a/net/can/isotp.c b/net/can/isotp.c
index 5e1c3971ebfc..5ae55ed28d57 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -1497,11 +1497,11 @@ static int isotp_release(struct socket *sock)
 	list_del(&so->notifier);
 	spin_unlock(&isotp_notifier_lock);
 
-	rtnl_lock();
 	lock_sock(sk);
 
 	/* remove current filters & unregister
-	 * tracked reference so->dev is taken at bind() time with rtnl_lock
+	 * the tracked reference so->dev keeps the device's receive lists
+	 * accessible, even after a namespace change
 	 */
 	if (so->bound && so->dev) {
 		if (isotp_register_rxid(so))
@@ -1519,8 +1519,6 @@ static int isotp_release(struct socket *sock)
 	so->bound = 0;
 	so->dev = NULL;
 
-	rtnl_unlock();
-
 	/* Always wait for a grace period before touching the timers below.
 	 * A concurrent NETDEV_UNREGISTER may have already unregistered our
 	 * filters and cleared so->bound in isotp_notify() without waiting
@@ -1588,7 +1586,7 @@ static int isotp_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int l
 	if (!addr->can_ifindex)
 		return -ENODEV;
 
-	rtnl_lock();
+	/* lock_sock() serializes the binding with isotp_notify() */
 	lock_sock(sk);
 
 	if (so->bound) {
@@ -1614,7 +1612,17 @@ static int isotp_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int l
 		goto out;
 	}
 
-	dev = dev_get_by_index(net, addr->can_ifindex);
+	/* Publish the device inside the RCU section of the lookup: When it
+	 * is unlisted concurrently, either isotp_notify() sees so->dev after
+	 * synchronize_net() or the lookup fails.
+	 */
+	rcu_read_lock();
+	dev = dev_get_by_index_rcu(net, addr->can_ifindex);
+	if (dev) {
+		dev_hold(dev);
+		WRITE_ONCE(so->dev, dev);
+	}
+	rcu_read_unlock();
 	if (!dev) {
 		err = -ENODEV;
 		goto out;
@@ -1627,7 +1635,7 @@ static int isotp_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int l
 		err = -EINVAL;
 		goto out_put_dev;
 	}
-	if (!(dev->flags & IFF_UP))
+	if (!(READ_ONCE(dev->flags) & IFF_UP))
 		notify_enetdown = 1;
 
 	ifindex = dev->ifindex;
@@ -1653,15 +1661,17 @@ static int isotp_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int l
 	 * can safely reach the device later, even if a concurrent
 	 * NETDEV_UNREGISTER has already unlisted it by ifindex.
 	 */
-	so->dev = dev;
 	netdev_hold(so->dev, &so->dev_tracker, GFP_KERNEL);
 
 out_put_dev:
-	/* remove potential reference from dev_get_by_index() */
+	/* the published so->dev is only valid for a successful bind() */
+	if (err)
+		WRITE_ONCE(so->dev, NULL);
+
+	/* remove reference from the device lookup */
 	dev_put(dev);
 out:
 	release_sock(sk);
-	rtnl_unlock();
 
 	if (notify_enetdown) {
 		sk->sk_err = ENETDOWN;
@@ -1864,12 +1874,18 @@ static void isotp_notify(struct isotp_sock *so, unsigned long msg,
 	if (!net_eq(dev_net(dev), sock_net(sk)))
 		return;
 
-	if (so->dev != dev)
+	/* lockless fast path, see raw_notify() */
+	if (READ_ONCE(so->dev) != dev)
 		return;
 
 	switch (msg) {
 	case NETDEV_UNREGISTER:
 		lock_sock(sk);
+		if (so->dev != dev) {
+			release_sock(sk);
+			break;
+		}
+
 		/* remove current filters & unregister */
 		if (so->bound) {
 			if (isotp_register_rxid(so))
@@ -1885,7 +1901,7 @@ static void isotp_notify(struct isotp_sock *so, unsigned long msg,
 
 		so->ifindex = 0;
 		so->bound  = 0;
-		so->dev = NULL;
+		WRITE_ONCE(so->dev, NULL);
 		release_sock(sk);
 
 		sk->sk_err = ENODEV;
diff --git a/net/can/raw.c b/net/can/raw.c
index dfea48768b23..0d8edfa772fb 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -85,6 +85,7 @@ struct raw_sock {
 	struct sock sk;
 	struct net_device *dev;
 	netdevice_tracker dev_tracker;
+	struct net_device *bind_dev; /* hint for raw_notify(), no reference */
 	struct list_head notifier;
 	int ifindex;
 	unsigned int bound:1;
@@ -224,6 +225,7 @@ static int raw_enable_filters(struct net *net, struct net_device *dev,
 	int i;
 
 	for (i = 0; i < count; i++) {
+		cond_resched();
 		err = can_rx_register(net, dev, filter[i].can_id,
 				      filter[i].can_mask,
 				      raw_rcv, sk, sock_i_ino(sk), sk);
@@ -258,9 +260,11 @@ static void raw_disable_filters(struct net *net, struct net_device *dev,
 {
 	int i;
 
-	for (i = 0; i < count; i++)
+	for (i = 0; i < count; i++) {
 		can_rx_unregister(net, dev, filter[i].can_id,
 				  filter[i].can_mask, raw_rcv, sk);
+		cond_resched();
+	}
 }
 
 static inline void raw_disable_errfilter(struct net *net,
@@ -305,16 +309,28 @@ static void raw_notify(struct raw_sock *ro, unsigned long msg,
 		       struct net_device *dev)
 {
 	struct sock *sk = &ro->sk;
+	struct net_device *bind_dev;
 
 	if (!net_eq(dev_net(dev), sock_net(sk)))
 		return;
 
-	if (ro->dev != dev)
+	/* Lockless fast path, ro->bind_dev covers a concurrent bind().
+	 * Read it before ro->dev, pairs with smp_store_release() in
+	 * raw_bind(). A stale ro->bind_dev only costs a lock_sock().
+	 */
+	bind_dev = smp_load_acquire(&ro->bind_dev);
+	if (READ_ONCE(ro->dev) != dev &&
+	    (msg != NETDEV_UNREGISTER || bind_dev != dev))
 		return;
 
 	switch (msg) {
 	case NETDEV_UNREGISTER:
 		lock_sock(sk);
+		if (ro->dev != dev) {
+			release_sock(sk);
+			break;
+		}
+
 		/* remove current filters & unregister */
 		if (ro->bound) {
 			raw_disable_allfilters(dev_net(dev), dev, sk);
@@ -326,7 +342,7 @@ static void raw_notify(struct raw_sock *ro, unsigned long msg,
 
 		ro->ifindex = 0;
 		ro->bound = 0;
-		ro->dev = NULL;
+		WRITE_ONCE(ro->dev, NULL);
 		ro->count = 0;
 		release_sock(sk);
 
@@ -381,6 +397,7 @@ static int raw_init(struct sock *sk)
 	ro->bound            = 0;
 	ro->ifindex          = 0;
 	ro->dev              = NULL;
+	ro->bind_dev         = NULL;
 
 	/* set default filter to single entry dfilter */
 	ro->dfilter.can_id   = 0;
@@ -431,13 +448,15 @@ static int raw_release(struct socket *sock)
 	list_del(&ro->notifier);
 	spin_unlock(&raw_notifier_lock);
 
-	rtnl_lock();
 	lock_sock(sk);
 
-	/* remove current filters & unregister */
+	/* remove current filters & unregister
+	 * the tracked reference ro->dev keeps the device's receive lists
+	 * accessible, even after a namespace change
+	 */
 	if (ro->bound) {
 		if (ro->dev) {
-			raw_disable_allfilters(dev_net(ro->dev), ro->dev, sk);
+			raw_disable_allfilters(net, ro->dev, sk);
 			netdev_put(ro->dev, &ro->dev_tracker);
 		} else {
 			raw_disable_allfilters(net, NULL, sk);
@@ -456,7 +475,6 @@ static int raw_release(struct socket *sock)
 	sock->sk = NULL;
 
 	release_sock(sk);
-	rtnl_unlock();
 
 	sock_prot_inuse_add(net, sk->sk_prot, -1);
 	sock_put(sk);
@@ -479,14 +497,25 @@ static int raw_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int len
 	if (addr->can_family != AF_CAN)
 		return -EINVAL;
 
-	rtnl_lock();
+	/* lock_sock() serializes the binding with raw_notify() */
 	lock_sock(sk);
 
 	if (ro->bound && addr->can_ifindex == ro->ifindex)
 		goto out;
 
 	if (addr->can_ifindex) {
-		dev = dev_get_by_index(sock_net(sk), addr->can_ifindex);
+		/* Publish the device inside the RCU section of the lookup:
+		 * When it is unlisted concurrently, either raw_notify() sees
+		 * ro->bind_dev after synchronize_net() or the lookup fails.
+		 */
+		rcu_read_lock();
+		dev = dev_get_by_index_rcu(sock_net(sk), addr->can_ifindex);
+		if (dev) {
+			dev_hold(dev);
+			/* pairs with smp_load_acquire() in raw_notify() */
+			smp_store_release(&ro->bind_dev, dev);
+		}
+		rcu_read_unlock();
 		if (!dev) {
 			err = -ENODEV;
 			goto out;
@@ -496,7 +525,7 @@ static int raw_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int len
 			goto out_put_dev;
 		}
 
-		if (!(dev->flags & IFF_UP))
+		if (!(READ_ONCE(dev->flags) & IFF_UP))
 			notify_enetdown = 1;
 
 		ifindex = dev->ifindex;
@@ -517,7 +546,7 @@ static int raw_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int len
 		if (ro->bound) {
 			/* unregister old filters */
 			if (ro->dev) {
-				raw_disable_allfilters(dev_net(ro->dev),
+				raw_disable_allfilters(sock_net(sk),
 						       ro->dev, sk);
 				/* drop reference to old ro->dev */
 				netdev_put(ro->dev, &ro->dev_tracker);
@@ -528,16 +557,15 @@ static int raw_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int len
 		ro->ifindex = ifindex;
 		ro->bound = 1;
 		/* bind() ok -> hold a reference for new ro->dev */
-		ro->dev = dev;
+		WRITE_ONCE(ro->dev, dev);
 		netdev_hold(ro->dev, &ro->dev_tracker, GFP_KERNEL);
 	}
 
 out_put_dev:
-	/* remove potential reference from dev_get_by_index() */
+	/* remove reference from the device lookup */
 	dev_put(dev);
 out:
 	release_sock(sk);
-	rtnl_unlock();
 
 	if (notify_enetdown) {
 		sk->sk_err = ENETDOWN;
@@ -566,58 +594,41 @@ static int raw_getname(struct socket *sock, struct sockaddr *uaddr,
 }
 
 static int raw_setsockopt_locked(struct socket *sock, int optname,
-				 sockptr_t optval, unsigned int optlen)
+				 sockptr_t optval, unsigned int optlen,
+				 struct can_filter *filter,
+				 struct can_filter *sfilter, int count)
 {
 	struct sock *sk = sock->sk;
 	struct raw_sock *ro = raw_sk(sk);
-	struct can_filter *filter = NULL;  /* dyn. alloc'ed filters */
-	struct can_filter sfilter;         /* single filter */
 	struct net_device *dev = NULL;
 	can_err_mask_t err_mask = 0;
-	int count = 0;
 	int flag;
 	int err = 0;
 
 	switch (optname) {
 	case CAN_RAW_FILTER:
-		if (optlen % sizeof(struct can_filter) != 0)
-			return -EINVAL;
-
-		if (optlen > CAN_RAW_FILTER_MAX * sizeof(struct can_filter))
-			return -EINVAL;
-
-		count = optlen / sizeof(struct can_filter);
-
-		if (count > 1) {
-			/* filter does not fit into dfilter => alloc space */
-			filter = memdup_sockptr(optval, optlen);
-			if (IS_ERR(filter))
-				return PTR_ERR(filter);
-		} else if (count == 1) {
-			if (copy_from_sockptr(&sfilter, optval, sizeof(sfilter)))
-				return -EFAULT;
-		}
-
+		/* @filter has been copied by raw_setsockopt(). It is linked
+		 * to the socket on success and freed by the caller on error.
+		 *
+		 * The reg_state check is only a shortcut: On a concurrent
+		 * unregistration or namespace change raw_notify() waits for
+		 * lock_sock() and removes the filters set here.
+		 */
 		dev = ro->dev;
-		if (ro->bound && dev && dev->reg_state != NETREG_REGISTERED) {
-			if (count > 1)
-				kfree(filter);
+		if (ro->bound && dev &&
+		    READ_ONCE(dev->reg_state) != NETREG_REGISTERED)
 			return -ENODEV;
-		}
 
 		if (ro->bound) {
 			/* (try to) register the new filters */
 			if (count == 1)
 				err = raw_enable_filters(sock_net(sk), dev, sk,
-							 &sfilter, 1);
+							 sfilter, 1);
 			else
 				err = raw_enable_filters(sock_net(sk), dev, sk,
 							 filter, count);
-			if (err) {
-				if (count > 1)
-					kfree(filter);
+			if (err)
 				return err;
-			}
 
 			/* remove old filter registrations */
 			raw_disable_filters(sock_net(sk), dev, sk, ro->filter,
@@ -631,7 +642,7 @@ static int raw_setsockopt_locked(struct socket *sock, int optname,
 		/* link new filters to the socket */
 		if (count == 1) {
 			/* copy filter data for single filter */
-			ro->dfilter = sfilter;
+			ro->dfilter = *sfilter;
 			filter = &ro->dfilter;
 		}
 		ro->filter = filter;
@@ -647,8 +658,10 @@ static int raw_setsockopt_locked(struct socket *sock, int optname,
 
 		err_mask &= CAN_ERR_MASK;
 
+		/* lockless shortcut, see CAN_RAW_FILTER */
 		dev = ro->dev;
-		if (ro->bound && dev && dev->reg_state != NETREG_REGISTERED)
+		if (ro->bound && dev &&
+		    READ_ONCE(dev->reg_state) != NETREG_REGISTERED)
 			return -ENODEV;
 
 		/* remove current error mask */
@@ -750,18 +763,47 @@ static int raw_setsockopt(struct socket *sock, int level, int optname,
 			  sockptr_t optval, unsigned int optlen)
 {
 	struct sock *sk = sock->sk;
+	struct can_filter *filter = NULL;  /* dyn. alloc'ed filters */
+	struct can_filter sfilter;         /* single filter */
+	int count = 0;
 	int err;
 
 	if (level != SOL_CAN_RAW)
 		return -EINVAL;
 
-	rtnl_lock();
+	if (optname == CAN_RAW_FILTER) {
+		/* Copy the filters before lock_sock(), so a stalled copy can
+		 * not block raw_notify() waiting for lock_sock() under RTNL.
+		 */
+		if (optlen % sizeof(struct can_filter) != 0)
+			return -EINVAL;
+
+		if (optlen > CAN_RAW_FILTER_MAX * sizeof(struct can_filter))
+			return -EINVAL;
+
+		count = optlen / sizeof(struct can_filter);
+
+		if (count > 1) {
+			/* filter does not fit into dfilter => alloc space */
+			filter = memdup_sockptr(optval, optlen);
+			if (IS_ERR(filter))
+				return PTR_ERR(filter);
+		} else if (count == 1) {
+			if (copy_from_sockptr(&sfilter, optval, sizeof(sfilter)))
+				return -EFAULT;
+		}
+	}
+
 	lock_sock(sk);
 
-	err = raw_setsockopt_locked(sock, optname, optval, optlen);
+	err = raw_setsockopt_locked(sock, optname, optval, optlen,
+				    filter, &sfilter, count);
 
 	release_sock(sk);
-	rtnl_unlock();
+
+	/* on error free the filters allocated for CAN_RAW_FILTER above */
+	if (err && count > 1)
+		kfree(filter);
 
 	return err;
 }
-- 
2.53.0

Re: [PATCH net-next 11/11] can: protect the receive lists with a per-device lock

[netdev-bot+sashiko]

Thank you for your contribution! Sashiko AI review found 3 potential
issue(s) to consider.

Critical: 0 · High: 0 · Medium: 1 · Low: 2

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] raw_bind() no longer holds RTNL, so the socket can miss a
  NETDEV_DOWN that arrives while it is binding.
- [Low] The commit message says "the callers pass the namespace that has
  been used for can_rx_register()", and the new kernel-doc of…
- [Low] The new comment on netns_can.rcvlists_lock in
  include/net/netns/can.h says it "protects rcv_lists_stats".

--

can: protect the receive lists with a per-device lock

This commit adds a spinlock to struct can_dev_rcv_lists. The receive lists
of a CAN device are now protected per device instead of by the per-netns
rcvlists_lock, so can_rx_unregister() still finds subscriptions after the
device has moved to another namespace. It also drops RTNL from raw_bind(),
raw_setsockopt(), raw_release(), isotp_bind() and isotp_release(), and
relies on lock_sock() plus a device pointer published inside the RCU
lookup to serialize with the netdev notifiers.

Link: https://lore.kernel.org/linux-can/CEA6A38A-2646-4ADA-95B4-CBAE2F301A8E@doyensec.com/
Link: https://patch.msgid.link/20261019152741.54854-6-socketcan@hartkopp.net

> diff --git a/include/net/netns/can.h b/include/net/netns/can.h
> index 48b79f7e6236..ef7aefdf7b23 100644
> --- a/include/net/netns/can.h
> +++ b/include/net/netns/can.h
> @@ -29,7 +29,7 @@ struct netns_can {
>  
>  	/* receive filters subscribed for 'all' CAN devices */
>  	struct can_dev_rcv_lists *rx_alldev_list;
> -	spinlock_t rcvlists_lock;
> +	spinlock_t rcvlists_lock; /* protects rcv_lists_stats */

[Severity: Low]
This isn't a bug, but is this comment accurate? The lock only serializes
the rcv_entries and rcv_entries_max updates in can_rx_register() and
can_rx_unregister().

can_init_stats() in net/can/proc.c updates other fields of the same
structure without taking rcvlists_lock. It runs from the stats timer, or
from the reset_stats proc read when the timer is disabled:

net/can/proc.c:can_init_stats() {
    ...
	rcv_lists_stats->stats_reset++;

	if (user_reset) {
		user_reset = 0;
		rcv_lists_stats->user_reset++;
	}
}

can_stats_proc_show() also reads these counters without the lock.

Could the comment name rcv_entries and rcv_entries_max specifically?

[ ... ]

> diff --git a/net/can/af_can.c b/net/can/af_can.c
> index d97f85fc3232..bf612c4b983d 100644
> --- a/net/can/af_can.c
> +++ b/net/can/af_can.c

[ ... ]

> @@ -509,6 +513,13 @@ static void can_rx_delete_receiver(struct rcu_head *rp)
>   *
>   * Description:
>   *  Removes subscription entry depending on given (subscription) values.
> + *  The receive lists of a CAN device are protected by a per-device lock,
> + *  so the subscription is found even when the device has been moved to
> + *  another network namespace after can_rx_register(). The caller has to
> + *  ensure that @dev stays valid, e.g. by holding a reference to @dev or
> + *  RTNL. @net is the namespace that has been used for can_rx_register().
> + *  It selects the 'any' CAN device lists for @dev == NULL and is used for
> + *  the receive list statistics.
>   */

[Severity: Low]
The new kernel-doc says @net is the namespace that was used for
can_rx_register(). The commit message says the same: "the callers pass
the namespace that has been used for can_rx_register()".

Does j1939 follow this? It reads dev_net(ndev) again at unregister time:

net/can/j1939/main.c:j1939_can_rx_register() {
    ...
	ret = can_rx_register(dev_net(ndev), ndev, J1939_CAN_ID, J1939_CAN_MASK,
			      j1939_can_recv, priv, 0, NULL);
    ...
}

net/can/j1939/main.c:j1939_can_rx_unregister() {
    ...
	can_rx_unregister(dev_net(ndev), ndev, J1939_CAN_ID, J1939_CAN_MASK,
			  j1939_can_recv, priv);
    ...
}

A j1939 registration can outlive a namespace move. j1939_sk_bind() does
not hold RTNL. It calls j1939_netdev_start(), which registers with the old
namespace, before it calls j1939_jsk_add().

Suppose the NETDEV_UNREGISTER from __dev_change_net_namespace() runs
j1939_sk_netdev_event_unregister() in that window. The socket is not
J1939_SOCK_BOUND yet, so it is skipped and the registration survives the
move. The final release then passes the new namespace:

j1939_netdev_stop()
  __j1939_rx_release()
    j1939_can_rx_unregister()
      can_rx_unregister(dev_net(ndev), ...)

The receiver is still found through the per-device lists. However,
rcv_entries is decremented in the new namespace's rcv_lists_stats
(clamped at 0) and stays elevated in the old one. This accounting matches
the behaviour before the patch.

Should j1939_priv store the registration namespace (with a netns
reference)? Or should the kernel-doc and commit message describe a looser
rule?

[ ... ]

> diff --git a/net/can/raw.c b/net/can/raw.c
> index dfea48768b23..0d8edfa772fb 100644
> --- a/net/can/raw.c
> +++ b/net/can/raw.c

[ ... ]

> @@ -305,16 +309,28 @@ static void raw_notify(struct raw_sock *ro, unsigned long msg,
>  		       struct net_device *dev)
>  {
>  	struct sock *sk = &ro->sk;
> +	struct net_device *bind_dev;
>  
>  	if (!net_eq(dev_net(dev), sock_net(sk)))
>  		return;
>  
> -	if (ro->dev != dev)
> +	/* Lockless fast path, ro->bind_dev covers a concurrent bind().
> +	 * Read it before ro->dev, pairs with smp_store_release() in
> +	 * raw_bind(). A stale ro->bind_dev only costs a lock_sock().
> +	 */
> +	bind_dev = smp_load_acquire(&ro->bind_dev);
> +	if (READ_ONCE(ro->dev) != dev &&
> +	    (msg != NETDEV_UNREGISTER || bind_dev != dev))
>  		return;

[Severity: Medium]
Can a NETDEV_DOWN be lost while raw_bind() is running? The bind_dev hint
is only checked for NETDEV_UNREGISTER, and raw_bind() no longer holds
RTNL.

raw_bind() now runs these steps in order:

    smp_store_release(&ro->bind_dev, dev);
    ...
    if (!(READ_ONCE(dev->flags) & IFF_UP))   /* device still up here */
        notify_enetdown = 1;
    ...
    err = raw_enable_allfilters(sock_net(sk), dev, sk);  /* cond_resched() */
    ...
    WRITE_ONCE(ro->dev, dev);

Suppose dev_close() runs after the IFF_UP check but before ro->dev is
published. raw_notifier()->raw_notify() then sees ro->dev != dev with
msg == NETDEV_DOWN, so it returns at the check above and never reaches
case NETDEV_DOWN. raw_bind() finishes with notify_enetdown == 0.

The socket ends up bound to a down interface, and sk_err = ENETDOWN /
sk_error_report() is never raised. Before this patch, rtnl_lock() in
raw_bind() kept dev_close() out of this window.

isotp_bind() publishes so->dev before it reads IFF_UP, so it does not seem
to have this problem.

Could raw_notify() also check bind_dev for NETDEV_DOWN? Alternatively,
raw_bind() could publish ro->dev before the IFF_UP check.

[ ... ]

-- 
Sashiko AI review · https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20261019170834.1727150-2-mkl%40pengutronix.de

Re: [PATCH net-next 11/11] can: protect the receive lists with a per-device lock

[Oliver Hartkopp]

On 20.10.26 19:11, netdev-bot+sashiko@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 3 potential
> issue(s) to consider.
> 
> Critical: 0 · High: 0 · Medium: 1 · Low: 2
> 
> 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] raw_bind() no longer holds RTNL, so the socket can miss a
>    NETDEV_DOWN that arrives while it is binding.
> - [Low] The commit message says "the callers pass the namespace that has
>    been used for can_rx_register()", and the new kernel-doc of…
> - [Low] The new comment on netns_can.rcvlists_lock in
>    include/net/netns/can.h says it "protects rcv_lists_stats".
> 

Thanks for the review.

[Medium] NETDEV_DOWN during raw_bind():

The window exists, but it only affects a down transition in the middle
of raw_bind(). Missing the asynchronous ENETDOWN there is harmless and
not worth an additional barrier pair in raw_bind() and raw_notify():

- Every transmission on a CAN_RAW socket goes through can_send(), which
   checks IFF_UP and returns -ENETDOWN to sendmsg(). So the state is
   reported reliably on every send attempt.

- The missed notification does not affect the binding: the CAN_RAW
   socket stays bound and its filters stay registered across down/up,
   and frames are received again once the interface is up.

- Applications can not rely on this notification anyway: a CAN_RAW
   socket bound to all CAN interfaces (ifindex 0) never gets ENETDOWN.
   Applications that need the link state have to track it via
   rtnetlink, not via the CAN socket.

[Low] rcvlists_lock comment / j1939 @net: These are documentation
details; the j1939 statistics behaviour is unchanged by this patch, as
noted in the patch description.

Best regards,
Oliver


> --
> 
> can: protect the receive lists with a per-device lock
> 
> This commit adds a spinlock to struct can_dev_rcv_lists. The receive lists
> of a CAN device are now protected per device instead of by the per-netns
> rcvlists_lock, so can_rx_unregister() still finds subscriptions after the
> device has moved to another namespace. It also drops RTNL from raw_bind(),
> raw_setsockopt(), raw_release(), isotp_bind() and isotp_release(), and
> relies on lock_sock() plus a device pointer published inside the RCU
> lookup to serialize with the netdev notifiers.
> 
> Link: https://lore.kernel.org/linux-can/CEA6A38A-2646-4ADA-95B4-CBAE2F301A8E@doyensec.com/
> Link: https://patch.msgid.link/20261019152741.54854-6-socketcan@hartkopp.net
> 
>> diff --git a/include/net/netns/can.h b/include/net/netns/can.h
>> index 48b79f7e6236..ef7aefdf7b23 100644
>> --- a/include/net/netns/can.h
>> +++ b/include/net/netns/can.h
>> @@ -29,7 +29,7 @@ struct netns_can {
>>   
>>   	/* receive filters subscribed for 'all' CAN devices */
>>   	struct can_dev_rcv_lists *rx_alldev_list;
>> -	spinlock_t rcvlists_lock;
>> +	spinlock_t rcvlists_lock; /* protects rcv_lists_stats */
> 
> [Severity: Low]
> This isn't a bug, but is this comment accurate? The lock only serializes
> the rcv_entries and rcv_entries_max updates in can_rx_register() and
> can_rx_unregister().
> 
> can_init_stats() in net/can/proc.c updates other fields of the same
> structure without taking rcvlists_lock. It runs from the stats timer, or
> from the reset_stats proc read when the timer is disabled:
> 
> net/can/proc.c:can_init_stats() {
>      ...
> 	rcv_lists_stats->stats_reset++;
> 
> 	if (user_reset) {
> 		user_reset = 0;
> 		rcv_lists_stats->user_reset++;
> 	}
> }
> 
> can_stats_proc_show() also reads these counters without the lock.
> 
> Could the comment name rcv_entries and rcv_entries_max specifically?
> 
> [ ... ]
> 
>> diff --git a/net/can/af_can.c b/net/can/af_can.c
>> index d97f85fc3232..bf612c4b983d 100644
>> --- a/net/can/af_can.c
>> +++ b/net/can/af_can.c
> 
> [ ... ]
> 
>> @@ -509,6 +513,13 @@ static void can_rx_delete_receiver(struct rcu_head *rp)
>>    *
>>    * Description:
>>    *  Removes subscription entry depending on given (subscription) values.
>> + *  The receive lists of a CAN device are protected by a per-device lock,
>> + *  so the subscription is found even when the device has been moved to
>> + *  another network namespace after can_rx_register(). The caller has to
>> + *  ensure that @dev stays valid, e.g. by holding a reference to @dev or
>> + *  RTNL. @net is the namespace that has been used for can_rx_register().
>> + *  It selects the 'any' CAN device lists for @dev == NULL and is used for
>> + *  the receive list statistics.
>>    */
> 
> [Severity: Low]
> The new kernel-doc says @net is the namespace that was used for
> can_rx_register(). The commit message says the same: "the callers pass
> the namespace that has been used for can_rx_register()".
> 
> Does j1939 follow this? It reads dev_net(ndev) again at unregister time:
> 
> net/can/j1939/main.c:j1939_can_rx_register() {
>      ...
> 	ret = can_rx_register(dev_net(ndev), ndev, J1939_CAN_ID, J1939_CAN_MASK,
> 			      j1939_can_recv, priv, 0, NULL);
>      ...
> }
> 
> net/can/j1939/main.c:j1939_can_rx_unregister() {
>      ...
> 	can_rx_unregister(dev_net(ndev), ndev, J1939_CAN_ID, J1939_CAN_MASK,
> 			  j1939_can_recv, priv);
>      ...
> }
> 
> A j1939 registration can outlive a namespace move. j1939_sk_bind() does
> not hold RTNL. It calls j1939_netdev_start(), which registers with the old
> namespace, before it calls j1939_jsk_add().
> 
> Suppose the NETDEV_UNREGISTER from __dev_change_net_namespace() runs
> j1939_sk_netdev_event_unregister() in that window. The socket is not
> J1939_SOCK_BOUND yet, so it is skipped and the registration survives the
> move. The final release then passes the new namespace:
> 
> j1939_netdev_stop()
>    __j1939_rx_release()
>      j1939_can_rx_unregister()
>        can_rx_unregister(dev_net(ndev), ...)
> 
> The receiver is still found through the per-device lists. However,
> rcv_entries is decremented in the new namespace's rcv_lists_stats
> (clamped at 0) and stays elevated in the old one. This accounting matches
> the behaviour before the patch.
> 
> Should j1939_priv store the registration namespace (with a netns
> reference)? Or should the kernel-doc and commit message describe a looser
> rule?
> 
> [ ... ]
> 
>> diff --git a/net/can/raw.c b/net/can/raw.c
>> index dfea48768b23..0d8edfa772fb 100644
>> --- a/net/can/raw.c
>> +++ b/net/can/raw.c
> 
> [ ... ]
> 
>> @@ -305,16 +309,28 @@ static void raw_notify(struct raw_sock *ro, unsigned long msg,
>>   		       struct net_device *dev)
>>   {
>>   	struct sock *sk = &ro->sk;
>> +	struct net_device *bind_dev;
>>   
>>   	if (!net_eq(dev_net(dev), sock_net(sk)))
>>   		return;
>>   
>> -	if (ro->dev != dev)
>> +	/* Lockless fast path, ro->bind_dev covers a concurrent bind().
>> +	 * Read it before ro->dev, pairs with smp_store_release() in
>> +	 * raw_bind(). A stale ro->bind_dev only costs a lock_sock().
>> +	 */
>> +	bind_dev = smp_load_acquire(&ro->bind_dev);
>> +	if (READ_ONCE(ro->dev) != dev &&
>> +	    (msg != NETDEV_UNREGISTER || bind_dev != dev))
>>   		return;
> 
> [Severity: Medium]
> Can a NETDEV_DOWN be lost while raw_bind() is running? The bind_dev hint
> is only checked for NETDEV_UNREGISTER, and raw_bind() no longer holds
> RTNL.
> 
> raw_bind() now runs these steps in order:
> 
>      smp_store_release(&ro->bind_dev, dev);
>      ...
>      if (!(READ_ONCE(dev->flags) & IFF_UP))   /* device still up here */
>          notify_enetdown = 1;
>      ...
>      err = raw_enable_allfilters(sock_net(sk), dev, sk);  /* cond_resched() */
>      ...
>      WRITE_ONCE(ro->dev, dev);
> 
> Suppose dev_close() runs after the IFF_UP check but before ro->dev is
> published. raw_notifier()->raw_notify() then sees ro->dev != dev with
> msg == NETDEV_DOWN, so it returns at the check above and never reaches
> case NETDEV_DOWN. raw_bind() finishes with notify_enetdown == 0.
> 
> The socket ends up bound to a down interface, and sk_err = ENETDOWN /
> sk_error_report() is never raised. Before this patch, rtnl_lock() in
> raw_bind() kept dev_close() out of this window.
> 
> isotp_bind() publishes so->dev before it reads IFF_UP, so it does not seem
> to have this problem.
> 
> Could raw_notify() also check bind_dev for NETDEV_DOWN? Alternatively,
> raw_bind() could publish ro->dev before the IFF_UP check.
> 
> [ ... ]
> 

Re: [PATCH net-next 11/11] can: protect the receive lists with a per-device lock

[Oliver Hartkopp]

On 20.10.26 21:00, Oliver Hartkopp wrote:
> 
> 
> On 20.10.26 19:11, netdev-bot+sashiko@kernel.org wrote:
>> Thank you for your contribution! Sashiko AI review found 3 potential
>> issue(s) to consider.
>>
>> Critical: 0 · High: 0 · Medium: 1 · Low: 2
>>
>> 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] raw_bind() no longer holds RTNL, so the socket can miss a
>>    NETDEV_DOWN that arrives while it is binding.
>> - [Low] The commit message says "the callers pass the namespace that has
>>    been used for can_rx_register()", and the new kernel-doc of…
>> - [Low] The new comment on netns_can.rcvlists_lock in
>>    include/net/netns/can.h says it "protects rcv_lists_stats".
>>
> 
> Thanks for the review.
> 
> [Medium] NETDEV_DOWN during raw_bind():
> 
> The window exists, but it only affects a down transition in the middle
> of raw_bind(). Missing the asynchronous ENETDOWN there is harmless and
> not worth an additional barrier pair in raw_bind() and raw_notify():


I did a closer look into it.

Although the missing of -ENETDOWN in raw_bind() is not a big issue it 
changes the former behaviour which is more relevant for reading from the 
CAN_RAW socket than writing to it.

 >> isotp_bind() publishes so->dev before it reads IFF_UP, so it does not
 >> seem to have this problem.

In fact both raw and isotp need smp_mb() to have the correct ordering.
I would bet a beer sashiko-bot would have remarked it next time :-/

While at it I also fixed the low severity commit and documentation 
remarks from sashiko-bot in patch 5 and patch 4.

New v5 patch set with updated cover letter for can-next is here:

https://lore.kernel.org/linux-can/20261020203257.230955-1-socketcan@hartkopp.net/

Best regards,
Oliver

pw-bot: cr

> 
> - Every transmission on a CAN_RAW socket goes through can_send(), which
>    checks IFF_UP and returns -ENETDOWN to sendmsg(). So the state is
>    reported reliably on every send attempt.
> 
> - The missed notification does not affect the binding: the CAN_RAW
>    socket stays bound and its filters stay registered across down/up,
>    and frames are received again once the interface is up.
> 
> - Applications can not rely on this notification anyway: a CAN_RAW
>    socket bound to all CAN interfaces (ifindex 0) never gets ENETDOWN.
>    Applications that need the link state have to track it via
>    rtnetlink, not via the CAN socket.
> 
> [Low] rcvlists_lock comment / j1939 @net: These are documentation
> details; the j1939 statistics behaviour is unchanged by this patch, as
> noted in the patch description.
> 
> Best regards,
> Oliver
> 
> 
>> -- 
>>
>> can: protect the receive lists with a per-device lock
>>
>> This commit adds a spinlock to struct can_dev_rcv_lists. The receive 
>> lists
>> of a CAN device are now protected per device instead of by the per-netns
>> rcvlists_lock, so can_rx_unregister() still finds subscriptions after the
>> device has moved to another namespace. It also drops RTNL from 
>> raw_bind(),
>> raw_setsockopt(), raw_release(), isotp_bind() and isotp_release(), and
>> relies on lock_sock() plus a device pointer published inside the RCU
>> lookup to serialize with the netdev notifiers.
>>
>> Link: https://lore.kernel.org/linux-can/CEA6A38A-2646-4ADA-95B4- 
>> CBAE2F301A8E@doyensec.com/
>> Link: https://patch.msgid.link/20261019152741.54854-6- 
>> socketcan@hartkopp.net
>>
>>> diff --git a/include/net/netns/can.h b/include/net/netns/can.h
>>> index 48b79f7e6236..ef7aefdf7b23 100644
>>> --- a/include/net/netns/can.h
>>> +++ b/include/net/netns/can.h
>>> @@ -29,7 +29,7 @@ struct netns_can {
>>>       /* receive filters subscribed for 'all' CAN devices */
>>>       struct can_dev_rcv_lists *rx_alldev_list;
>>> -    spinlock_t rcvlists_lock;
>>> +    spinlock_t rcvlists_lock; /* protects rcv_lists_stats */
>>
>> [Severity: Low]
>> This isn't a bug, but is this comment accurate? The lock only serializes
>> the rcv_entries and rcv_entries_max updates in can_rx_register() and
>> can_rx_unregister().
>>
>> can_init_stats() in net/can/proc.c updates other fields of the same
>> structure without taking rcvlists_lock. It runs from the stats timer, or
>> from the reset_stats proc read when the timer is disabled:
>>
>> net/can/proc.c:can_init_stats() {
>>      ...
>>     rcv_lists_stats->stats_reset++;
>>
>>     if (user_reset) {
>>         user_reset = 0;
>>         rcv_lists_stats->user_reset++;
>>     }
>> }
>>
>> can_stats_proc_show() also reads these counters without the lock.
>>
>> Could the comment name rcv_entries and rcv_entries_max specifically?
>>
>> [ ... ]
>>
>>> diff --git a/net/can/af_can.c b/net/can/af_can.c
>>> index d97f85fc3232..bf612c4b983d 100644
>>> --- a/net/can/af_can.c
>>> +++ b/net/can/af_can.c
>>
>> [ ... ]
>>
>>> @@ -509,6 +513,13 @@ static void can_rx_delete_receiver(struct 
>>> rcu_head *rp)
>>>    *
>>>    * Description:
>>>    *  Removes subscription entry depending on given (subscription) 
>>> values.
>>> + *  The receive lists of a CAN device are protected by a per-device 
>>> lock,
>>> + *  so the subscription is found even when the device has been moved to
>>> + *  another network namespace after can_rx_register(). The caller 
>>> has to
>>> + *  ensure that @dev stays valid, e.g. by holding a reference to 
>>> @dev or
>>> + *  RTNL. @net is the namespace that has been used for 
>>> can_rx_register().
>>> + *  It selects the 'any' CAN device lists for @dev == NULL and is 
>>> used for
>>> + *  the receive list statistics.
>>>    */
>>
>> [Severity: Low]
>> The new kernel-doc says @net is the namespace that was used for
>> can_rx_register(). The commit message says the same: "the callers pass
>> the namespace that has been used for can_rx_register()".
>>
>> Does j1939 follow this? It reads dev_net(ndev) again at unregister time:
>>
>> net/can/j1939/main.c:j1939_can_rx_register() {
>>      ...
>>     ret = can_rx_register(dev_net(ndev), ndev, J1939_CAN_ID, 
>> J1939_CAN_MASK,
>>                   j1939_can_recv, priv, 0, NULL);
>>      ...
>> }
>>
>> net/can/j1939/main.c:j1939_can_rx_unregister() {
>>      ...
>>     can_rx_unregister(dev_net(ndev), ndev, J1939_CAN_ID, J1939_CAN_MASK,
>>               j1939_can_recv, priv);
>>      ...
>> }
>>
>> A j1939 registration can outlive a namespace move. j1939_sk_bind() does
>> not hold RTNL. It calls j1939_netdev_start(), which registers with the 
>> old
>> namespace, before it calls j1939_jsk_add().
>>
>> Suppose the NETDEV_UNREGISTER from __dev_change_net_namespace() runs
>> j1939_sk_netdev_event_unregister() in that window. The socket is not
>> J1939_SOCK_BOUND yet, so it is skipped and the registration survives the
>> move. The final release then passes the new namespace:
>>
>> j1939_netdev_stop()
>>    __j1939_rx_release()
>>      j1939_can_rx_unregister()
>>        can_rx_unregister(dev_net(ndev), ...)
>>
>> The receiver is still found through the per-device lists. However,
>> rcv_entries is decremented in the new namespace's rcv_lists_stats
>> (clamped at 0) and stays elevated in the old one. This accounting matches
>> the behaviour before the patch.
>>
>> Should j1939_priv store the registration namespace (with a netns
>> reference)? Or should the kernel-doc and commit message describe a looser
>> rule?
>>
>> [ ... ]
>>
>>> diff --git a/net/can/raw.c b/net/can/raw.c
>>> index dfea48768b23..0d8edfa772fb 100644
>>> --- a/net/can/raw.c
>>> +++ b/net/can/raw.c
>>
>> [ ... ]
>>
>>> @@ -305,16 +309,28 @@ static void raw_notify(struct raw_sock *ro, 
>>> unsigned long msg,
>>>                  struct net_device *dev)
>>>   {
>>>       struct sock *sk = &ro->sk;
>>> +    struct net_device *bind_dev;
>>>       if (!net_eq(dev_net(dev), sock_net(sk)))
>>>           return;
>>> -    if (ro->dev != dev)
>>> +    /* Lockless fast path, ro->bind_dev covers a concurrent bind().
>>> +     * Read it before ro->dev, pairs with smp_store_release() in
>>> +     * raw_bind(). A stale ro->bind_dev only costs a lock_sock().
>>> +     */
>>> +    bind_dev = smp_load_acquire(&ro->bind_dev);
>>> +    if (READ_ONCE(ro->dev) != dev &&
>>> +        (msg != NETDEV_UNREGISTER || bind_dev != dev))
>>>           return;
>>
>> [Severity: Medium]
>> Can a NETDEV_DOWN be lost while raw_bind() is running? The bind_dev hint
>> is only checked for NETDEV_UNREGISTER, and raw_bind() no longer holds
>> RTNL.
>>
>> raw_bind() now runs these steps in order:
>>
>>      smp_store_release(&ro->bind_dev, dev);
>>      ...
>>      if (!(READ_ONCE(dev->flags) & IFF_UP))   /* device still up here */
>>          notify_enetdown = 1;
>>      ...
>>      err = raw_enable_allfilters(sock_net(sk), dev, sk);  /* 
>> cond_resched() */
>>      ...
>>      WRITE_ONCE(ro->dev, dev);
>>
>> Suppose dev_close() runs after the IFF_UP check but before ro->dev is
>> published. raw_notifier()->raw_notify() then sees ro->dev != dev with
>> msg == NETDEV_DOWN, so it returns at the check above and never reaches
>> case NETDEV_DOWN. raw_bind() finishes with notify_enetdown == 0.
>>
>> The socket ends up bound to a down interface, and sk_err = ENETDOWN /
>> sk_error_report() is never raised. Before this patch, rtnl_lock() in
>> raw_bind() kept dev_close() out of this window.
>>
>> isotp_bind() publishes so->dev before it reads IFF_UP, so it does not 
>> seem
>> to have this problem.
>>
>> Could raw_notify() also check bind_dev for NETDEV_DOWN? Alternatively,
>> raw_bind() could publish ro->dev before the IFF_UP check.
>>
>> [ ... ]
>>
> 
>