[PATCH net] net: expect instance lock in netdev_queue_get_dma_dev()

[PATCH net] net: expect instance lock in netdev_queue_get_dma_dev()

[Jakub Kicinski]

netdev_queue_get_dma_dev() uses "compat" locking assert which wants
either the rtnl_lock or netdev instance lock. This is not right,
the callers are taking the instance lock unconditionally. All entry
points for queue config are purely instance locked.

In other words the callers use netdev_get_by_index_lock(), not
netdev_get_by_index_lock_ops_compat(). All the state we will
access is effectively instance lock protected (it's const for
devices which are not ops-locked).

Update the assert to avoid false positive warnings.

Cc: stable@vger.kernel.org
Fixes: b6c5f9454ef34 ("io_uring/zcrx: call netdev_queue_get_dma_dev() under instance lock")
Reported-by: syzbot+a78926bdac2adb52dc0e@syzkaller.appspotmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
CC: axboe@kernel.dk
CC: io-uring@vger.kernel.org
CC: asml.silence@gmail.com
---
 net/core/netdev_queues.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/netdev_queues.c b/net/core/netdev_queues.c
index 4d6864bb4f6b..f5558b12877c 100644
--- a/net/core/netdev_queues.c
+++ b/net/core/netdev_queues.c
@@ -40,7 +40,7 @@ struct device *netdev_queue_get_dma_dev(struct net_device *dev,
 	struct netdev_rx_queue *hw_rxq;
 	struct device *dma_dev;
 
-	netdev_assert_locked_ops_compat(dev);
+	netdev_assert_locked(dev);
 
 	/* Only RX side supports queue leasing today. */
 	if (type != NETDEV_QUEUE_TYPE_RX || !netif_rxq_is_leased(dev, idx))
-- 
2.55.0

Re: [PATCH net] net: expect instance lock in netdev_queue_get_dma_dev()

[Simon Horman]

On Thu, Aug 06, 2026 at 03:56:26PM -0700, Jakub Kicinski wrote:
> netdev_queue_get_dma_dev() uses "compat" locking assert which wants
> either the rtnl_lock or netdev instance lock. This is not right,
> the callers are taking the instance lock unconditionally. All entry
> points for queue config are purely instance locked.
> 
> In other words the callers use netdev_get_by_index_lock(), not
> netdev_get_by_index_lock_ops_compat(). All the state we will
> access is effectively instance lock protected (it's const for
> devices which are not ops-locked).
> 
> Update the assert to avoid false positive warnings.
> 
> Cc: stable@vger.kernel.org
> Fixes: b6c5f9454ef34 ("io_uring/zcrx: call netdev_queue_get_dma_dev() under instance lock")
> Reported-by: syzbot+a78926bdac2adb52dc0e@syzkaller.appspotmail.com
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Reviewed-by: Simon Horman <horms@kernel.org>

Re: [PATCH net] net: expect instance lock in netdev_queue_get_dma_dev()

[Daniel Borkmann]

On 8/7/26 12:56 AM, Jakub Kicinski wrote:
> netdev_queue_get_dma_dev() uses "compat" locking assert which wants
> either the rtnl_lock or netdev instance lock. This is not right,
> the callers are taking the instance lock unconditionally. All entry
> points for queue config are purely instance locked.
> 
> In other words the callers use netdev_get_by_index_lock(), not
> netdev_get_by_index_lock_ops_compat(). All the state we will
> access is effectively instance lock protected (it's const for
> devices which are not ops-locked).
> 
> Update the assert to avoid false positive warnings.
> 
> Cc: stable@vger.kernel.org
> Fixes: b6c5f9454ef34 ("io_uring/zcrx: call netdev_queue_get_dma_dev() under instance lock")
> Reported-by: syzbot+a78926bdac2adb52dc0e@syzkaller.appspotmail.com
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>

Re: [PATCH net] net: expect instance lock in netdev_queue_get_dma_dev()

[patchwork-bot+netdevbpf]

Hello:

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

On Thu,  6 Aug 2026 15:56:26 -0700 you wrote:
> netdev_queue_get_dma_dev() uses "compat" locking assert which wants
> either the rtnl_lock or netdev instance lock. This is not right,
> the callers are taking the instance lock unconditionally. All entry
> points for queue config are purely instance locked.
> 
> In other words the callers use netdev_get_by_index_lock(), not
> netdev_get_by_index_lock_ops_compat(). All the state we will
> access is effectively instance lock protected (it's const for
> devices which are not ops-locked).
> 
> [...]

Here is the summary with links:
  - [net] net: expect instance lock in netdev_queue_get_dma_dev()
    https://git.kernel.org/netdev/net/c/92465f46f3c3

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html