[PATCH 4.14 016/101] net/wan: fix a double free in x25_asy_open_tty()

From: Greg Kroah-Hartman
Date: Mon Jan 07 2019 - 08:00:15 EST

4.14-stable review patch. If anyone has any objections, please let me know.


From: Cong Wang <xiyou.wangcong@xxxxxxxxx>

[ Upstream commit d5c7c745f254c6cb98b3b3f15fe789b8bd770c72 ]

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@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 3b780bed3138 ("x25_asy: Free x25_asy on x25_asy_open() failure.")
Signed-off-by: Cong Wang <xiyou.wangcong@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
drivers/net/wan/x25_asy.c | 2 ++
1 file changed, 2 insertions(+)

--- 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_devic

/* Cleanup */
+ sl->xbuff = NULL;
+ sl->rbuff = NULL;
return -ENOMEM;