From: Pavel Skripkin <paskripkin@gmail.com>
Date: Tue, 8 Jun 2021 08:06:41 +0000 (+0300)
Subject: net: rds: fix memory leak in rds_recvmsg
X-Git-Tag: v4.4.274~40
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8c3ec88b03e9e4ca117dcdc4204fd3edcd02084f;p=thirdparty%2Fkernel%2Fstable.git

net: rds: fix memory leak in rds_recvmsg

[ Upstream commit 49bfcbfd989a8f1f23e705759a6bb099de2cff9f ]

Syzbot reported memory leak in rds. The problem
was in unputted refcount in case of error.

int rds_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
		int msg_flags)
{
...

	if (!rds_next_incoming(rs, &inc)) {
		...
	}

After this "if" inc refcount incremented and

	if (rds_cmsg_recv(inc, msg, rs)) {
		ret = -EFAULT;
		goto out;
	}
...
out:
	return ret;
}

in case of rds_cmsg_recv() fail the refcount won't be
decremented. And it's easy to see from ftrace log, that
rds_inc_addref() don't have rds_inc_put() pair in
rds_recvmsg() after rds_cmsg_recv()

 1)               |  rds_recvmsg() {
 1)   3.721 us    |    rds_inc_addref();
 1)   3.853 us    |    rds_message_inc_copy_to_user();
 1) + 10.395 us   |    rds_cmsg_recv();
 1) + 34.260 us   |  }

Fixes: bdbe6fbc6a2f ("RDS: recv.c")
Reported-and-tested-by: syzbot+5134cdf021c4ed5aaa5f@syzkaller.appspotmail.com
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Reviewed-by: Håkon Bugge <haakon.bugge@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/net/rds/recv.c b/net/rds/recv.c
index 9bf812509e0e9..1ff4bc3237f01 100644
--- a/net/rds/recv.c
+++ b/net/rds/recv.c
@@ -482,7 +482,7 @@ int rds_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
 
 		if (rds_cmsg_recv(inc, msg)) {
 			ret = -EFAULT;
-			goto out;
+			break;
 		}
 
 		rds_stats_inc(s_recv_delivered);