[PATCH net] af_unix: Fix a data-race in unix_dgram_peer_wake_me().

From: Kuniyuki Iwashima <kuniyu@amazon.com>
To: "David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Rainer Weikusat <rweikusat@mobileactivedefense.com>
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>,
	Kuniyuki Iwashima <kuni1840@gmail.com>, <netdev@vger.kernel.org>
Subject: [PATCH net] af_unix: Fix a data-race in unix_dgram_peer_wake_me().
Date: Sun, 5 Jun 2022 16:23:25 -0700	[thread overview]
Message-ID: <20220605232325.11804-1-kuniyu@amazon.com> (raw)

unix_dgram_poll() calls unix_dgram_peer_wake_me() without `other`'s
lock held and check if its receive queue is full.  Here we need to
use unix_recvq_full_lockless() instead of unix_recvq_full(), otherwise
KCSAN will report a data-race.

Fixes: 7d267278a9ec ("unix: avoid use-after-free in ep_remove_wait_queue")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
As Eric noted in commit 04f08eb44b501, I think rest of unix_recvq_full()
can be turned into the lockless version.  After this merge window, I can
send a follow-up patch if there is no objection.
---
 net/unix/af_unix.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 654dcef7cfb3..2206e6f8902d 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -490,7 +490,7 @@ static int unix_dgram_peer_wake_me(struct sock *sk, struct sock *other)
 	 * -ECONNREFUSED. Otherwise, if we haven't queued any skbs
 	 * to other and its full, we will hang waiting for POLLOUT.
 	 */
-	if (unix_recvq_full(other) && !sock_flag(other, SOCK_DEAD))
+	if (unix_recvq_full_lockless(other) && !sock_flag(other, SOCK_DEAD))
 		return 1;
 
 	if (connected)
-- 
2.30.2

