5.4-stable review patch. If anyone has any objections, please let me know.
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From: Kuniyuki Iwashima kuniyu@amazon.com
[ Upstream commit 3a0f38eb285c8c2eead4b3230c7ac2983707599d ]
ioctl(SIOCINQ) calls unix_inq_len() that checks sk->sk_state first and returns -EINVAL if it's TCP_LISTEN.
Then, for SOCK_STREAM sockets, unix_inq_len() returns the number of bytes in recvq.
However, unix_inq_len() does not hold unix_state_lock(), and the concurrent listen() might change the state after checking sk->sk_state.
If the race occurs, 0 is returned for the listener, instead of -EINVAL, because the length of skb with embryo is 0.
We could hold unix_state_lock() in unix_inq_len(), but it's overkill given the result is true for pre-listen() TCP_CLOSE state.
So, let's use READ_ONCE() for sk->sk_state in unix_inq_len().
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Kuniyuki Iwashima kuniyu@amazon.com Signed-off-by: Paolo Abeni pabeni@redhat.com 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 e8bad973285e4..8ab1e2a781195 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -2579,7 +2579,7 @@ long unix_inq_len(struct sock *sk) struct sk_buff *skb; long amount = 0;
- if (sk->sk_state == TCP_LISTEN) + if (READ_ONCE(sk->sk_state) == TCP_LISTEN) return -EINVAL;
spin_lock(&sk->sk_receive_queue.lock);