Re: net/unix: sk_socket can disappear when state is unlocked
From: Hannes Frederic Sowa <hidden>
Date: 2015-05-22 09:50:37
Also in:
lkml
On Do, 2015-05-21 at 09:25 -0700, Mark Salyzyn wrote:
quoted hunk ↗ jump to hunk
got a rare NULL pointer dereference in clear_bit Signed-off-by: Mark Salyzyn <redacted> --- net/unix/af_unix.c | 5 +++++ 1 file changed, 5 insertions(+)diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 5266ea7..37a8925 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c@@ -1880,6 +1880,11 @@ static long unix_stream_data_wait(struct sock *sk, long timeo, unix_state_unlock(sk); timeo = freezable_schedule_timeout(timeo); unix_state_lock(sk); + + /* sk_socket may have been killed while unlocked */ + if (!sk->sk_socket) + break; + clear_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags); }
Canonical way is to test for sock_flag(sk, SOCK_DEAD). Also it does not seem like we are returning an error to user space but are still looping to try to dequeue skbs from sk_receive_queue, which is concurrently emptied by unix_release (maybe, without holding unix_state_lock). Bye, Hannes