Subject: [PATCH 38/45] netrom: hold sock when setting skb->destructor

From: Cong Wang <[email-masked]>
Date: Mon, 22 Jul 2019 20:41:22 -0700

[ Upstream commit 4638faac032756f7eab5524be7be56bee77e426b ]

sock_efree() releases the sock refcnt, if we don't hold this refcnt
when setting skb->destructor to it, the refcnt would not be balanced.
This leads to several bug reports from syzbot.

I have checked other users of sock_efree(), all of them hold the
sock refcnt.

Fixes: c8c8218ec5af ("netrom: fix a memory leak in nr_rx_frame()")
Reported-and-tested-by: <[email-masked]>
Reported-and-tested-by: <[email-masked]>
Reported-and-tested-by: <[email-masked]>
Reported-and-tested-by: <[email-masked]>
Cc: Ralf Baechle <[email-masked]>
Signed-off-by: Cong Wang <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 net/netrom/af_netrom.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/netrom/af_netrom.c b/net/netrom/af_netrom.c
index f11b6747e18c..43910e50752c 100644
--- a/net/netrom/af_netrom.c
+++ b/net/netrom/af_netrom.c
@@ -970,6 +970,7 @@ int nr_rx_frame(struct sk_buff *skb, struct net_device *dev)
 
 	window = skb->data[20];
 
+	sock_hold(make);
 	skb->sk             = make;
 	skb->destructor     = sock_efree;
 	make->sk_state	    = TCP_ESTABLISHED;
-- 
2.20.1