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From:   Jia-Ju Bai <baijiaju1990@gmail.com>
To:     davem@davemloft.net, sbrivio@redhat.com, sd@queasysnail.net,
        liuhangbin@gmail.com, jbenc@redhat.com, dsahern@gmail.com,
        natechancellor@gmail.com, tglx@linutronix.de
Cc:     netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        Jia-Ju Bai <baijiaju1990@gmail.com>
Subject: [PATCH] net: geneve: Fix a possible null-pointer dereference in geneve_link_config()
Date:   Mon, 29 Jul 2019 18:26:11 +0800
Message-Id: <20190729102611.2338-1-baijiaju1990@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

In geneve_link_config(), there is an if statement on line 1524 to check
whether rt is NULL:
    if (rt && rt->dst.dev)

When rt is NULL, it is used on line 1526:
    ip6_rt_put(rt)
        dst_release(&rt->dst);

Thus, a possible null-pointer dereference may occur.

To fix this bug, ip6_rt_put(rt) 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>
---
 drivers/net/geneve.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
index cb2ea8facd8d..a47a1b31b166 100644
--- a/drivers/net/geneve.c
+++ b/drivers/net/geneve.c
@@ -1521,9 +1521,10 @@ static void geneve_link_config(struct net_device *dev,
 		rt = rt6_lookup(geneve->net, &info->key.u.ipv6.dst, NULL, 0,
 				NULL, 0);
 
-		if (rt && rt->dst.dev)
+		if (rt && rt->dst.dev) {
 			ldev_mtu = rt->dst.dev->mtu - GENEVE_IPV6_HLEN;
-		ip6_rt_put(rt);
+			ip6_rt_put(rt);
+		}
 		break;
 	}
 #endif
-- 
2.17.0