From 1747aa98ab136b7a2aad2735270c93a94d2c9453 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Tue, 9 May 2023 16:35:53 +0000
Subject: [PATCH] net: annotate sk->sk_err write from do_recvmmsg()

[ Upstream commit e05a5f510f26607616fecdd4ac136310c8bea56b ]

do_recvmmsg() can write to sk->sk_err from multiple threads.

As said before, many other points reading or writing sk_err
need annotations.

Fixes: 34b88a68f26a ("net: Fix use after free in the recvmmsg exit path")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/socket.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/socket.c b/net/socket.c
index 02feaf5bd84a..9dd4c7ce8343 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -2723,7 +2723,7 @@ static int do_recvmmsg(int fd, struct mmsghdr __user *mmsg,
 		 * error to return on the next call or if the
 		 * app asks about it using getsockopt(SO_ERROR).
 		 */
-		sock->sk->sk_err = -err;
+		WRITE_ONCE(sock->sk->sk_err, -err);
 	}
 out_put:
 	fput_light(sock->file, fput_needed);