2019-07-29 10:28:40

by Jia-Ju Bai

Subject: [PATCH] net: geneve: Fix a possible null-pointer dereference in geneve_link_config()

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 <[email protected]>
---
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

2019-07-29 10:32:36

by Jiri Benc

Subject: Re: [PATCH] net: geneve: Fix a possible null-pointer dereference in geneve_link_config()

On Mon, 29 Jul 2019 18:26:11 +0800, Jia-Ju Bai wrote:
> --- 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

Are you sure rt6_lookup can never return a non-NULL rt with rt->dst.dev
being NULL? You'd leak the reference in such case.

Jiri

2019-07-29 10:53:14

by Jiri Benc

Subject: Re: [PATCH] net: geneve: Fix a possible null-pointer dereference in geneve_link_config()

On Mon, 29 Jul 2019 12:30:55 +0200, Jiri Benc wrote:
> Are you sure rt6_lookup can never return a non-NULL rt with rt->dst.dev
> being NULL? You'd leak the reference in such case.

In fact, you're introducing a bug, not fixing one. ip6_rt_put does
accept NULL parameter. And it seems you already have been told that?

Nacked-by: Jiri Benc <[email protected]>

Jiri