[PATCH 4.9 20/71] net: rds: fix memory leak in rds_recvmsg

Sasha Levin
2021-06-28T15:19:34Z

From: Pavel Skripkin <paskripkin@gmail.com>

[ 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>
---
net/rds/recv.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/rds/recv.c b/net/rds/recv.c
index 488a198be3e1..4bd307e31b40 100644
--- a/net/rds/recv.c
+++ b/net/rds/recv.c
@@ -596,7 +596,7 @@ int rds_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,

if (rds_cmsg_recv(inc, msg, rs)) {
ret = -EFAULT;
- goto out;
+ break;
}

rds_stats_inc(s_recv_delivered);
--
2.30.2