netdev - [PATCH net-next 6/6] af_unix: annotate lockless accesses to sk->sk

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Date:   Wed, 15 Mar 2023 20:57:46 +0000
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 6/6] af_unix: annotate lockless accesses to sk->sk_err

unix_poll() and unix_dgram_poll() read sk->sk_err
without any lock held.

Add relevant READ_ONCE()/WRITE_ONCE() annotations.

Signed-off-by: Eric Dumazet <edumazet@...gle.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 0b0f18ecce4470d6fd21c084a3ea49e04dcbb9bd..fb31e8a4409ed979e4443e7d3d392a5e0f2c424b 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -557,7 +557,7 @@ static void unix_dgram_disconnected(struct sock *sk, struct sock *other)
 		 * when peer was not connected to us.
 		 */
 		if (!sock_flag(other, SOCK_DEAD) && unix_peer(other) == sk) {
-			other->sk_err = ECONNRESET;
+			WRITE_ONCE(other->sk_err, ECONNRESET);
 			sk_error_report(other);
 		}
 	}
@@ -630,7 +630,7 @@ static void unix_release_sock(struct sock *sk, int embrion)
 			/* No more writes */
 			skpair->sk_shutdown = SHUTDOWN_MASK;
 			if (!skb_queue_empty(&sk->sk_receive_queue) || embrion)
-				skpair->sk_err = ECONNRESET;
+				WRITE_ONCE(skpair->sk_err, ECONNRESET);
 			unix_state_unlock(skpair);
 			skpair->sk_state_change(skpair);
 			sk_wake_async(skpair, SOCK_WAKE_WAITD, POLL_HUP);
@@ -3165,7 +3165,7 @@ static __poll_t unix_poll(struct file *file, struct socket *sock, poll_table *wa
 	mask = 0;
 
 	/* exceptional events? */
-	if (sk->sk_err)
+	if (READ_ONCE(sk->sk_err))
 		mask |= EPOLLERR;
 	if (sk->sk_shutdown == SHUTDOWN_MASK)
 		mask |= EPOLLHUP;
@@ -3208,7 +3208,8 @@ static __poll_t unix_dgram_poll(struct file *file, struct socket *sock,
 	mask = 0;
 
 	/* exceptional events? */
-	if (sk->sk_err || !skb_queue_empty_lockless(&sk->sk_error_queue))
+	if (READ_ONCE(sk->sk_err) ||
+	    !skb_queue_empty_lockless(&sk->sk_error_queue))
 		mask |= EPOLLERR |
 			(sock_flag(sk, SOCK_SELECT_ERR_QUEUE) ? EPOLLPRI : 0);
 
-- 
2.40.0.rc2.332.ga46443480c-goog