6.8-stable review patch. If anyone has any objections, please let me know.
------------------
From: Kuniyuki Iwashima kuniyu@amazon.com
[ 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
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 --- net/unix/af_unix.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index fd931f3005cd8..9df15a7bc2569 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -2602,7 +2602,9 @@ 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))) @@ -2684,11 +2686,9 @@ 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