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

Commit d4a1875ddd1e ("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: d4a1875ddd1e ("af_unix: Add unix_stream_proto for sockmap")
Reported-by: Casey Schaufler <casey@schaufler-ca.com>
Suggested-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Jiang Wang <jiang.wang@bytedance.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20211004232530.2377085-1-jiang.wang@bytedance.com

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index f505b89bda6adefe973806f842001d428fc6c5ca..915afcae6a121d3bd0b56535d9643ebe4700d5a0 100644 (file)
--- a/net/unix/af_unix.c
+++ b/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);