[PATCH v1 net] net: Use rtnl_net_dev_lock() in register_netdevice_notifier_dev_net().

[PATCH v1 net] net: Use rtnl_net_dev_lock() in register_netdevice_notifier_dev_net().

[Kuniyuki Iwashima]

Breno Leitao reported the splat below. [0]

Commit 65161fb544aa ("net: Fix dev_net(dev) race in
unregister_netdevice_notifier_dev_net().") added the
DEBUG_NET_WARN_ON_ONCE(), assuming that the netdev is not
registered before register_netdevice_notifier_dev_net().

But the assumption was simply wrong.

Let's use rtnl_net_dev_lock() in register_netdevice_notifier_dev_net().

[0]:
WARNING: CPU: 25 PID: 849 at net/core/dev.c:2150 register_netdevice_notifier_dev_net (net/core/dev.c:2150)
 <TASK>
 ? __warn (kernel/panic.c:242 kernel/panic.c:748)
 ? register_netdevice_notifier_dev_net (net/core/dev.c:2150)
 ? register_netdevice_notifier_dev_net (net/core/dev.c:2150)
 ? report_bug (lib/bug.c:? lib/bug.c:219)
 ? handle_bug (arch/x86/kernel/traps.c:285)
 ? exc_invalid_op (arch/x86/kernel/traps.c:309)
 ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:621)
 ? register_netdevice_notifier_dev_net (net/core/dev.c:2150)
 ? register_netdevice_notifier_dev_net (./include/net/net_namespace.h:406 ./include/linux/netdevice.h:2663 net/core/dev.c:2144)
 mlx5e_mdev_notifier_event+0x9f/0xf0 mlx5_ib
 notifier_call_chain.llvm.12241336988804114627 (kernel/notifier.c:85)
 blocking_notifier_call_chain (kernel/notifier.c:380)
 mlx5_core_uplink_netdev_event_replay (drivers/net/ethernet/mellanox/mlx5/core/main.c:352)
 mlx5_ib_roce_init.llvm.12447516292400117075+0x1c6/0x550 mlx5_ib
 mlx5r_probe+0x375/0x6a0 mlx5_ib
 ? kernfs_put (./include/linux/instrumented.h:96 ./include/linux/atomic/atomic-arch-fallback.h:2278 ./include/linux/atomic/atomic-instrumented.h:1384 fs/kernfs/dir.c:557)
 ? auxiliary_match_id (drivers/base/auxiliary.c:174)
 ? mlx5r_mp_remove+0x160/0x160 mlx5_ib
 really_probe (drivers/base/dd.c:? drivers/base/dd.c:658)
 driver_probe_device (drivers/base/dd.c:830)
 __driver_attach (drivers/base/dd.c:1217)
 bus_for_each_dev (drivers/base/bus.c:369)
 ? driver_attach (drivers/base/dd.c:1157)
 bus_add_driver (drivers/base/bus.c:679)
 driver_register (drivers/base/driver.c:249)

Fixes: 7fb1073300a2 ("net: Hold rtnl_net_lock() in (un)?register_netdevice_notifier_dev_net().")
Reported-by: Breno Leitao <leitao@debian.org>
Closes: https://lore.kernel.org/netdev/20250224-noisy-cordial-roadrunner-fad40c@leitao/
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 net/core/dev.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 1b252e9459fd..70c01bd1799e 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2141,21 +2141,15 @@ int register_netdevice_notifier_dev_net(struct net_device *dev,
 					struct notifier_block *nb,
 					struct netdev_net_notifier *nn)
 {
-	struct net *net = dev_net(dev);
 	int err;
 
-	/* rtnl_net_lock() assumes dev is not yet published by
-	 * register_netdevice().
-	 */
-	DEBUG_NET_WARN_ON_ONCE(!list_empty(&dev->dev_list));
-
-	rtnl_net_lock(net);
-	err = __register_netdevice_notifier_net(net, nb, false);
+	rtnl_net_dev_lock(dev);
+	err = __register_netdevice_notifier_net(dev_net(dev), nb, false);
 	if (!err) {
 		nn->nb = nb;
 		list_add(&nn->list, &dev->net_notifier_list);
 	}
-	rtnl_net_unlock(net);
+	rtnl_net_dev_unlock(dev);
 
 	return err;
 }
-- 
2.39.5 (Apple Git-154)

Re: [PATCH v1 net] net: Use rtnl_net_dev_lock() in register_netdevice_notifier_dev_net().

[Eric Dumazet]

On Tue, Feb 25, 2025 at 10:10 PM Kuniyuki Iwashima <kuniyu@amazon.com> wrote:
>
> Breno Leitao reported the splat below. [0]
>
> Commit 65161fb544aa ("net: Fix dev_net(dev) race in
> unregister_netdevice_notifier_dev_net().") added the
> DEBUG_NET_WARN_ON_ONCE(), assuming that the netdev is not
> registered before register_netdevice_notifier_dev_net().
>
> But the assumption was simply wrong.
>
> Let's use rtnl_net_dev_lock() in register_netdevice_notifier_dev_net().
>
> [0]:
> WARNING: CPU: 25 PID: 849 at net/core/dev.c:2150 register_netdevice_notifier_dev_net (net/core/dev.c:2150)
>  <TASK>
>
> ---

Reviewed-by: Eric Dumazet <edumazet@google.com>

Re: [PATCH v1 net] net: Use rtnl_net_dev_lock() in register_netdevice_notifier_dev_net().

[Breno Leitao]

On Tue, Feb 25, 2025 at 01:10:23PM -0800, Kuniyuki Iwashima wrote:
> Breno Leitao reported the splat below. [0]
> 
> Commit 65161fb544aa ("net: Fix dev_net(dev) race in
> unregister_netdevice_notifier_dev_net().") added the
> DEBUG_NET_WARN_ON_ONCE(), assuming that the netdev is not
> registered before register_netdevice_notifier_dev_net().
> 
> But the assumption was simply wrong.
> 
> Let's use rtnl_net_dev_lock() in register_netdevice_notifier_dev_net().
> 
> [0]:
> WARNING: CPU: 25 PID: 849 at net/core/dev.c:2150 register_netdevice_notifier_dev_net (net/core/dev.c:2150)
>  <TASK>
>  ? __warn (kernel/panic.c:242 kernel/panic.c:748)
>  ? register_netdevice_notifier_dev_net (net/core/dev.c:2150)
>  ? register_netdevice_notifier_dev_net (net/core/dev.c:2150)
>  ? report_bug (lib/bug.c:? lib/bug.c:219)
>  ? handle_bug (arch/x86/kernel/traps.c:285)
>  ? exc_invalid_op (arch/x86/kernel/traps.c:309)
>  ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:621)
>  ? register_netdevice_notifier_dev_net (net/core/dev.c:2150)
>  ? register_netdevice_notifier_dev_net (./include/net/net_namespace.h:406 ./include/linux/netdevice.h:2663 net/core/dev.c:2144)
>  mlx5e_mdev_notifier_event+0x9f/0xf0 mlx5_ib
>  notifier_call_chain.llvm.12241336988804114627 (kernel/notifier.c:85)
>  blocking_notifier_call_chain (kernel/notifier.c:380)
>  mlx5_core_uplink_netdev_event_replay (drivers/net/ethernet/mellanox/mlx5/core/main.c:352)
>  mlx5_ib_roce_init.llvm.12447516292400117075+0x1c6/0x550 mlx5_ib
>  mlx5r_probe+0x375/0x6a0 mlx5_ib
>  ? kernfs_put (./include/linux/instrumented.h:96 ./include/linux/atomic/atomic-arch-fallback.h:2278 ./include/linux/atomic/atomic-instrumented.h:1384 fs/kernfs/dir.c:557)
>  ? auxiliary_match_id (drivers/base/auxiliary.c:174)
>  ? mlx5r_mp_remove+0x160/0x160 mlx5_ib
>  really_probe (drivers/base/dd.c:? drivers/base/dd.c:658)
>  driver_probe_device (drivers/base/dd.c:830)
>  __driver_attach (drivers/base/dd.c:1217)
>  bus_for_each_dev (drivers/base/bus.c:369)
>  ? driver_attach (drivers/base/dd.c:1157)
>  bus_add_driver (drivers/base/bus.c:679)
>  driver_register (drivers/base/driver.c:249)
> 
> Fixes: 7fb1073300a2 ("net: Hold rtnl_net_lock() in (un)?register_netdevice_notifier_dev_net().")
> Reported-by: Breno Leitao <leitao@debian.org>
> Closes: https://lore.kernel.org/netdev/20250224-noisy-cordial-roadrunner-fad40c@leitao/
> Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>

Tested-by: Breno Leitao <leitao@debian.org>

Re: [PATCH v1 net] net: Use rtnl_net_dev_lock() in register_netdevice_notifier_dev_net().

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Tue, 25 Feb 2025 13:10:23 -0800 you wrote:
> Breno Leitao reported the splat below. [0]
> 
> Commit 65161fb544aa ("net: Fix dev_net(dev) race in
> unregister_netdevice_notifier_dev_net().") added the
> DEBUG_NET_WARN_ON_ONCE(), assuming that the netdev is not
> registered before register_netdevice_notifier_dev_net().
> 
> [...]

Here is the summary with links:
  - [v1,net] net: Use rtnl_net_dev_lock() in register_netdevice_notifier_dev_net().
    https://git.kernel.org/netdev/net/c/01c9c123db76

You are awesome, thank you!
-- 
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