[PATCH net v3] af_unix: Reject SIOCATMARK on non-stream sockets

[PATCH net v3] af_unix: Reject SIOCATMARK on non-stream sockets

[Ren Wei]

From: Jiexun Wang <wangjiexun2025@gmail.com>

SIOCATMARK reports whether the receive queue is at the urgent mark for
MSG_OOB.

In AF_UNIX, MSG_OOB is supported only for SOCK_STREAM sockets.
SOCK_DGRAM and SOCK_SEQPACKET reject MSG_OOB in sendmsg() and recvmsg(),
so they should not support SIOCATMARK either.

Return -EOPNOTSUPP for non-stream sockets before checking the receive
queue.

Fixes: 314001f0bf92 ("af_unix: Add OOB support")
Cc: stable@kernel.org
Reported-by: Yuan Tan <yuantan098@gmail.com>
Reported-by: Yifan Wu <yifanwucs@gmail.com>
Reported-by: Juefei Pu <tomapufckgml@gmail.com>
Reported-by: Xin Liu <bird@lzu.edu.cn>
Suggested-by: Kuniyuki Iwashima <kuniyu@google.com>
Signed-off-by: Jiexun Wang <wangjiexun2025@gmail.com>
Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
---
Changes in v3:
- Update trailers.
- v2 Link: https://lore.kernel.org/all/20260413122916.1479959-1-n05ec@lzu.edu.cn/

Changes in v2:
- Rework the fix based on maintainer feedback.
- Drop the receive-queue locking approach and reject SIOCATMARK on
  non-stream sockets instead, since it is only meaningful for MSG_OOB.
- v1 Link: https://lore.kernel.org/netdev/f6cbbc8da90e95584847b5ceb60aae830d1631c2.1775731983.git.wangjiexun2025@gmail.com/

 net/unix/af_unix.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index e2d787ca3e74..1cbf36ea043b 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -3323,6 +3323,9 @@ static int unix_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
 			struct sk_buff *skb;
 			int answ = 0;
 
+			if (sk->sk_type != SOCK_STREAM)
+				return -EOPNOTSUPP;
+
 			mutex_lock(&u->iolock);
 
 			skb = skb_peek(&sk->sk_receive_queue);
-- 
2.34.1

Re: [PATCH net v3] af_unix: Reject SIOCATMARK on non-stream sockets

[Kuniyuki Iwashima]

On Wed, May 6, 2026 at 7:08 AM Ren Wei <n05ec@lzu.edu.cn> wrote:
>
> From: Jiexun Wang <wangjiexun2025@gmail.com>
>
> SIOCATMARK reports whether the receive queue is at the urgent mark for
> MSG_OOB.
>
> In AF_UNIX, MSG_OOB is supported only for SOCK_STREAM sockets.
> SOCK_DGRAM and SOCK_SEQPACKET reject MSG_OOB in sendmsg() and recvmsg(),
> so they should not support SIOCATMARK either.
>
> Return -EOPNOTSUPP for non-stream sockets before checking the receive
> queue.
>
> Fixes: 314001f0bf92 ("af_unix: Add OOB support")
> Cc: stable@kernel.org
> Reported-by: Yuan Tan <yuantan098@gmail.com>
> Reported-by: Yifan Wu <yifanwucs@gmail.com>
> Reported-by: Juefei Pu <tomapufckgml@gmail.com>
> Reported-by: Xin Liu <bird@lzu.edu.cn>
> Suggested-by: Kuniyuki Iwashima <kuniyu@google.com>
> Signed-off-by: Jiexun Wang <wangjiexun2025@gmail.com>
> Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>

Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>

Re: [PATCH net v3] af_unix: Reject SIOCATMARK on non-stream sockets

[patchwork-bot+netdevbpf]

Hello:

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

On Wed,  6 May 2026 22:08:23 +0800 you wrote:
> From: Jiexun Wang <wangjiexun2025@gmail.com>
> 
> SIOCATMARK reports whether the receive queue is at the urgent mark for
> MSG_OOB.
> 
> In AF_UNIX, MSG_OOB is supported only for SOCK_STREAM sockets.
> SOCK_DGRAM and SOCK_SEQPACKET reject MSG_OOB in sendmsg() and recvmsg(),
> so they should not support SIOCATMARK either.
> 
> [...]

Here is the summary with links:
  - [net,v3] af_unix: Reject SIOCATMARK on non-stream sockets
    https://git.kernel.org/netdev/net/c/d119775f2bad

You are awesome, thank you!
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