linux-kernel - [PATCH bpf v1] unix: fix an issue in unix_shutdown causing the other end read/write failures

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Date:   Mon,  4 Oct 2021 23:25:28 +0000
From:   Jiang Wang <jiang.wang@...edance.com>
To:     bpf@...r.kernel.org
Cc:     cong.wang@...edance.com, Casey Schaufler <casey@...aufler-ca.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Eric Dumazet <edumazet@...gle.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Rao Shoaib <Rao.Shoaib@...cle.com>,
        Kuniyuki Iwashima <kuniyu@...zon.co.jp>,
        Jakub Sitnicki <jakub@...udflare.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH bpf v1] unix: fix an issue in unix_shutdown causing the other end read/write failures

Commit 94531cfcbe79 ("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: 94531cfcbe79 (af_unix: Add unix_stream_proto for sockmap)
Suggested-by: Cong Wang <cong.wang@...edance.com>
Reported-by: Casey Schaufler <casey@...aufler-ca.com>
Signed-off-by: Jiang Wang <jiang.wang@...edance.com>
---
 net/unix/af_unix.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index efac5989edb5..0878ab86597b 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -2882,6 +2882,9 @@ 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);
@@ -2904,12 +2907,10 @@ 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);
-- 
2.20.1