netdev - [PATCH net] net: annotate sk->sk_err write from do

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Message-ID: <20230509163553.3081476-1-edumazet@google.com>
Date: Tue,  9 May 2023 16:35:53 +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>, syzbot <syzkaller@...glegroups.com>
Subject: [PATCH net] net: annotate sk->sk_err write from do_recvmmsg()

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@...gle.com>
Reported-by: syzbot <syzkaller@...glegroups.com>
---
 net/socket.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/socket.c b/net/socket.c
index a7b4b37d86df7a9232d582a14863c05b5fd34b68..b7e01d0fe0824d1f277c1fe70f68f09a10319832 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -2911,7 +2911,7 @@ 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);
-- 
2.40.1.521.gf1e218fcd8-goog