af_unix: Fix a data-race in unix_dgram_peer_wake_me().

stable inclusion
from stable-4.19.247
commit 95f0ba806277733bf6024e23e27e1be773701cca
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5FNPY
CVE: NA

--------------------------------

[ Upstream commit 662a8094 ]

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: 7d267278 ("unix: avoid use-after-free in ep_remove_wait_queue")
Signed-off-by: NKuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20220605232325.11804-1-kuniyu@amazon.comSigned-off-by: NPaolo Abeni <pabeni@redhat.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYongqiang Liu <liuyongqiang13@huawei.com>
Signed-off-by: NLaibin Qiu <qiulaibin@huawei.com>

net/unix/af_unix.c

@@ -445,7 +445,7 @@ 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)