[PATCH net v2 1/1] af_unix: Reject SIOCATMARK on non-stream sockets

[Ren Wei <n05ec@lzu.edu.cn>]

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")
Reported-by: Yifan Wu <yifanwucs@gmail.com>
Reported-by: Juefei Pu <tomapufckgml@gmail.com>
Co-developed-by: Yuan Tan <yuantan098@gmail.com>
Signed-off-by: Yuan Tan <yuantan098@gmail.com>
Suggested-by: Xin Liu <bird@lzu.edu.cn>
Tested-by: Ren Wei <enjou1224z@gmail.com>
Signed-off-by: Jiexun Wang <wangjiexun2025@gmail.com>
Signed-off-by: Ren Wei <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 b23c33df8b46..09d43b4813b1 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -3300,6 +3300,9 @@ 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