unix: Fix an issue in unix_shutdown causing the other end read/write failures

Commit 94531cf ("af_unix: Add unix_stream_proto for sockmap") sets
unix domain socket peer state to TCP_CLOSE in unix_shutdown. This could
happen when the local end is shutdown but the other end is not. Then,
the other end will get read or write failures which is not expected.
Fix the issue by setting the local state to shutdown.

Fixes: 94531cf ("af_unix: Add unix_stream_proto for sockmap")
Reported-by: Casey Schaufler <[email protected]>
Suggested-by: Cong Wang <[email protected]>
Signed-off-by: Jiang Wang <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>
Tested-by: Casey Schaufler <[email protected]>
Reviewed-by: Casey Schaufler <[email protected]>
Acked-by: Song Liu <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]

Author: Jiang-BD

net/unix/af_unix.c

@@ -2860,6 +2860,9 @@ static int unix_shutdown(struct socket *sock, int mode)
 
 	unix_state_lock(sk);
 	sk->sk_shutdown |= mode;
+	if ((sk->sk_type == SOCK_STREAM || sk->sk_type == SOCK_SEQPACKET) &&
+	    mode == SHUTDOWN_MASK)
+		sk->sk_state = TCP_CLOSE;
 	other = unix_peer(sk);
 	if (other)
 		sock_hold(other);
@@ -2882,12 +2885,10 @@ static int unix_shutdown(struct socket *sock, int mode)
 		other->sk_shutdown |= peer_mode;
 		unix_state_unlock(other);
 		other->sk_state_change(other);
-		if (peer_mode == SHUTDOWN_MASK) {
+		if (peer_mode == SHUTDOWN_MASK)
 			sk_wake_async(other, SOCK_WAKE_WAITD, POLL_HUP);
-			other->sk_state = TCP_CLOSE;
-		} else if (peer_mode & RCV_SHUTDOWN) {
+		else if (peer_mode & RCV_SHUTDOWN)
 			sk_wake_async(other, SOCK_WAKE_WAITD, POLL_IN);
-		}
 	}
 	if (other)
 		sock_put(other);