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From:   Jia-Ju Bai <baijiaju1990@gmail.com>
To:     davem@davemloft.net, kuznet@ms2.inr.ac.ru, yoshfuji@linux-ipv6.org
Cc:     netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        Jia-Ju Bai <baijiaju1990@gmail.com>
Subject: [PATCH 2/2] net: ipv6: Fix a possible null-pointer dereference in vti6_link_config()
Date:   Fri, 26 Jul 2019 16:03:21 +0800
Message-Id: <20190726080321.4466-1-baijiaju1990@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

In vti6_link_config(), there is an if statement on line 649 to check
whether rt is NULL:
    if (rt)

When rt is NULL, it is used on line 651:
    ip6_rt_put(rt);
        dst_release(&rt->dst);

Thus, a possible null-pointer dereference may occur.

To fix this bug, ip6_rt_put() is called when rt is not NULL.

This bug is found by a static analysis tool STCheck written by us.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
 net/ipv6/ip6_vti.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c
index 024db17386d2..572647205c52 100644
--- a/net/ipv6/ip6_vti.c
+++ b/net/ipv6/ip6_vti.c
@@ -646,9 +646,10 @@ static void vti6_link_config(struct ip6_tnl *t, bool keep_mtu)
 						 &p->raddr, &p->laddr,
 						 p->link, NULL, strict);
 
-		if (rt)
+		if (rt) {
 			tdev = rt->dst.dev;
-		ip6_rt_put(rt);
+			ip6_rt_put(rt);
+		}
 	}
 
 	if (!tdev && p->link)
-- 
2.17.0