6.1-stable review patch. If anyone has any objections, please let me know.
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From: Kuniyuki Iwashima kuniyu@amazon.com
[ Upstream commit 26bfb8b57063f52b867f9b6c8d1742fcb5bd656c ]
When a SOCK_DGRAM socket connect()s to another socket, the both sockets' sk->sk_state are changed to TCP_ESTABLISHED so that we can register them to BPF SOCKMAP.
When the socket disconnects from the peer by connect(AF_UNSPEC), the state is set back to TCP_CLOSE.
Then, the peer's state is also set to TCP_CLOSE, but the update is done locklessly and unconditionally.
Let's say socket A connect()ed to B, B connect()ed to C, and A disconnects from B.
After the first two connect()s, all three sockets' sk->sk_state are TCP_ESTABLISHED:
$ ss -xa Netid State Recv-Q Send-Q Local Address:Port Peer Address:PortProcess u_dgr ESTAB 0 0 @A 641 * 642 u_dgr ESTAB 0 0 @B 642 * 643 u_dgr ESTAB 0 0 @C 643 * 0
And after the disconnect, B's state is TCP_CLOSE even though it's still connected to C and C's state is TCP_ESTABLISHED.
$ ss -xa Netid State Recv-Q Send-Q Local Address:Port Peer Address:PortProcess u_dgr UNCONN 0 0 @A 641 * 0 u_dgr UNCONN 0 0 @B 642 * 643 u_dgr ESTAB 0 0 @C 643 * 0
In this case, we cannot register B to SOCKMAP.
So, when a socket disconnects from the peer, we should not set TCP_CLOSE to the peer if the peer is connected to yet another socket, and this must be done under unix_state_lock().
Note that we use WRITE_ONCE() for sk->sk_state as there are many lockless readers. These data-races will be fixed in the following patches.
Fixes: 83301b5367a9 ("af_unix: Set TCP_ESTABLISHED for datagram sockets too") 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 | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 7d2a3b42b456a..5d6203b6e25c3 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -558,7 +558,6 @@ static void unix_dgram_disconnected(struct sock *sk, struct sock *other) sk_error_report(other); } } - other->sk_state = TCP_CLOSE; }
static void unix_sock_destructor(struct sock *sk) @@ -1412,8 +1411,15 @@ static int unix_dgram_connect(struct socket *sock, struct sockaddr *addr,
unix_state_double_unlock(sk, other);
- if (other != old_peer) + if (other != old_peer) { unix_dgram_disconnected(sk, old_peer); + + unix_state_lock(old_peer); + if (!unix_peer(old_peer)) + WRITE_ONCE(old_peer->sk_state, TCP_CLOSE); + unix_state_unlock(old_peer); + } + sock_put(old_peer); } else { unix_peer(sk) = other;