netdev - [Patch net] net/wan: fix a double free in x25_asy_open

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Date:   Sat, 29 Dec 2018 13:56:37 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     netdev@...r.kernel.org
Cc:     Cong Wang <xiyou.wangcong@...il.com>
Subject: [Patch net] net/wan: fix a double free in x25_asy_open_tty()

When x25_asy_open() fails, it already cleans up by itself,
so its caller doesn't need to free the memory again.

It seems we still have to call x25_asy_free() to clear the SLF_INUSE
bit, so just set these pointers to NULL after kfree().

Reported-and-tested-by: syzbot+5e5e969e525129229052@...kaller.appspotmail.com
Fixes: 3b780bed3138 ("x25_asy: Free x25_asy on x25_asy_open() failure.")
Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
---
 drivers/net/wan/x25_asy.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/wan/x25_asy.c b/drivers/net/wan/x25_asy.c
index 1098263ab862..46c3d983b7b7 100644
--- a/drivers/net/wan/x25_asy.c
+++ b/drivers/net/wan/x25_asy.c
@@ -485,8 +485,10 @@ static int x25_asy_open(struct net_device *dev)
 
 	/* Cleanup */
 	kfree(sl->xbuff);
+	sl->xbuff = NULL;
 noxbuff:
 	kfree(sl->rbuff);
+	sl->rbuff = NULL;
 norbuff:
 	return -ENOMEM;
 }
-- 
2.19.2