UPSTREAM: af_unix: Don't peek OOB data without MSG_OOB. [ Upstream commit 22dd70eb2c3d754862964377a75abafd3167346b ] Currently, we can read OOB data without MSG_OOB by using MSG_PEEK when OOB data is sitting on the front row, which is apparently wrong. >>> from socket import * >>> c1, c2 = socketpair(AF_UNIX, SOCK_STREAM) >>> c1.send(b'a', MSG_OOB) 1 >>> c2.recv(1, MSG_PEEK | MSG_DONTWAIT) b'a' If manage_oob() is called when no data has been copied, we only check if the socket enables SO_OOBINLINE or MSG_PEEK is not used. Otherwise, the skb is returned as is. However, here we should return NULL if MSG_PEEK is set and no data has been copied. Also, in such a case, we should not jump to the redo label because we will be caught in the loop and hog the CPU until normal data comes in. Then, we need to handle skb == NULL case with the if-clause below the manage_oob() block. With this patch: >>> from socket import * >>> c1, c2 = socketpair(AF_UNIX, SOCK_STREAM) >>> c1.send(b'a', MSG_OOB) 1 >>> c2.recv(1, MSG_PEEK | MSG_DONTWAIT) Traceback (most recent call last): File "<stdin>", line 1, in <module> BlockingIOError: [Errno 11] Resource temporarily unavailable Bug: 342490466 Fixes: 314001f0bf92 ("af_unix: Add OOB support") Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> Link: https://lore.kernel.org/r/20240410171016.7621-3-kuniyu@amazon.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> (cherry picked from commit 022d81a709cd553bbe2db8675f8e824f4aee6284) Signed-off-by: Lee Jones <joneslee@google.com> Change-Id: I4728977f8f908c19dfa5c861c7381a50499b7fe0 diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index f07fafd..4130f34 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c
@@ -2677,7 +2677,9 @@ static struct sk_buff *manage_oob(struct sk_buff *skb, struct sock *sk, WRITE_ONCE(u->oob_skb, NULL); consume_skb(skb); } - } else if (!(flags & MSG_PEEK)) { + } else if (flags & MSG_PEEK) { + skb = NULL; + } else { skb_unlink(skb, &sk->sk_receive_queue); WRITE_ONCE(u->oob_skb, NULL); if (!WARN_ON_ONCE(skb_unref(skb))) @@ -2758,11 +2760,9 @@ static int unix_stream_read_generic(struct unix_stream_read_state *state, #if IS_ENABLED(CONFIG_AF_UNIX_OOB) if (skb) { skb = manage_oob(skb, sk, flags, copied); - if (!skb) { + if (!skb && copied) { unix_state_unlock(sk); - if (copied) - break; - goto redo; + break; } } #endif 