[PATCH 5.15 22/71] af_unix: Call manage_oob() for every skb in unix_stream_read_generic().

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

5.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ Upstream commit 283454c8a123072e5c386a5a2b5fc576aa455b6f ]

When we call recv() for AF_UNIX socket, we first peek one skb and
calls manage_oob() to check if the skb is sent with MSG_OOB.

However, when we fetch the next (and the following) skb, manage_oob()
is not called now, leading a wrong behaviour.

Let's say a socket send()s "hello" with MSG_OOB and the peer tries
to recv() 5 bytes with MSG_PEEK.  Here, we should get only "hell"
without 'o', but actually not:

  >>> from socket import *
  >>> c1, c2 = socketpair(AF_UNIX, SOCK_STREAM)
  >>> c1.send(b'hello', MSG_OOB)
  5
  >>> c2.recv(5, MSG_PEEK)
  b'hello'

The first skb fills 4 bytes, and the next skb is peeked but not
properly checked by manage_oob().

Let's move up the again label to call manage_oob() for evry skb.

With this patch:

  >>> from socket import *
  >>> c1, c2 = socketpair(AF_UNIX, SOCK_STREAM)
  >>> c1.send(b'hello', MSG_OOB)
  5
  >>> c2.recv(5, MSG_PEEK)
  b'hell'

Fixes: 314001f0bf92 ("af_unix: Add OOB support")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20240410171016.7621-2-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/unix/af_unix.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 628d97c195a7e..e2a2e22d210f6 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -2644,6 +2644,7 @@ static int unix_stream_read_generic(struct unix_stream_read_state *state,
 		last = skb = skb_peek(&sk->sk_receive_queue);
 		last_len = last ? last->len : 0;
 
+again:
 #if IS_ENABLED(CONFIG_AF_UNIX_OOB)
 		if (skb) {
 			skb = manage_oob(skb, sk, flags, copied);
@@ -2655,7 +2656,6 @@ static int unix_stream_read_generic(struct unix_stream_read_state *state,
 			}
 		}
 #endif
-again:
 		if (skb == NULL) {
 			if (copied >= target)
 				goto unlock;
-- 
2.43.0