[PATCH 4.4 094/158] netrom: hold sock when setting skb->destructor

[Greg Kroah-Hartman]

From: Cong Wang <xiyou.wangc...@gmail.com>

[ 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: <syzbot+622bdabb128acc334...@syzkaller.appspotmail.com>
Reported-and-tested-by: <syzbot+6eaef7158b19e3fec...@syzkaller.appspotmail.com>
Reported-and-tested-by: <syzbot+9399c158fcc09b21d...@syzkaller.appspotmail.com>
Reported-and-tested-by: <syzbot+a34e5f3d0300163f0...@syzkaller.appspotmail.com>
Cc: Ralf Baechle <r...@linux-mips.org>
Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 net/netrom/af_netrom.c |    1 +
 1 file changed, 1 insertion(+)

--- a/net/netrom/af_netrom.c
+++ b/net/netrom/af_netrom.c
@@ -968,6 +968,7 @@ int nr_rx_frame(struct sk_buff *skb, str
 
        window = skb->data[20];
 
+       sock_hold(make);
        skb->sk             = make;
        skb->destructor     = sock_efree;
        make->sk_state      = TCP_ESTABLISHED;