From: Soheil Hassas Yeganeh <soheil@google.com>
Date: Tue, 27 Feb 2018 23:22:40 +0000 (-0500)
Subject: socket: skip checking sk_err for recvmmsg(MSG_ERRQUEUE)
X-Git-Tag: v4.17-rc1~148^2~318
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=7797dc41417eb0e03f39fc4356f7635bcdef108e;p=linux.git

socket: skip checking sk_err for recvmmsg(MSG_ERRQUEUE)

recvmmsg does not call ___sys_recvmsg when sk_err is set.
That is fine for normal reads but, for MSG_ERRQUEUE, recvmmsg
should always call ___sys_recvmsg regardless of sk->sk_err to
be able to clear error queue. Otherwise, users are not able to
drain the error queue using recvmmsg.

Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/socket.c b/net/socket.c
index 645d32b4872c..d9a1ac233b35 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -2289,10 +2289,12 @@ int __sys_recvmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
 	if (!sock)
 		return err;
 
-	err = sock_error(sock->sk);
-	if (err) {
-		datagrams = err;
-		goto out_put;
+	if (likely(!(flags & MSG_ERRQUEUE))) {
+		err = sock_error(sock->sk);
+		if (err) {
+			datagrams = err;
+			goto out_put;
+		}
 	}
 
 	entry = mmsg;