netdev - [Patch net] netrom: hold sock when setting skb->destructor

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Date:   Mon, 22 Jul 2019 20:41:22 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     netdev@...r.kernel.org
Cc:     Cong Wang <xiyou.wangcong@...il.com>,
        syzbot+622bdabb128acc33427d@...kaller.appspotmail.com,
        syzbot+6eaef7158b19e3fec3a0@...kaller.appspotmail.com,
        syzbot+9399c158fcc09b21d0d2@...kaller.appspotmail.com,
        syzbot+a34e5f3d0300163f0c87@...kaller.appspotmail.com,
        Ralf Baechle <ralf@...ux-mips.org>
Subject: [Patch net] netrom: hold sock when setting skb->destructor

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+622bdabb128acc33427d@...kaller.appspotmail.com>
Reported-and-tested-by: <syzbot+6eaef7158b19e3fec3a0@...kaller.appspotmail.com>
Reported-and-tested-by: <syzbot+9399c158fcc09b21d0d2@...kaller.appspotmail.com>
Reported-and-tested-by: <syzbot+a34e5f3d0300163f0c87@...kaller.appspotmail.com>
Cc: Ralf Baechle <ralf@...ux-mips.org>
Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
---
 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 96740d389377..c4f54ad2b98a 100644
--- a/net/netrom/af_netrom.c
+++ b/net/netrom/af_netrom.c
@@ -967,6 +967,7 @@ 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;
-- 
2.21.0