2019-07-26 08:06:17

by Jia-Ju Bai

Subject: [PATCH 2/2] net: ipv6: Fix a possible null-pointer dereference in vti6_link_config()

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 <[email protected]>
---
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

2019-07-26 09:22:58

by Nicolas Dichtel

Subject: Re: [PATCH 2/2] net: ipv6: Fix a possible null-pointer dereference in vti6_link_config()

Le 26/07/2019 à 10:03, Jia-Ju Bai a écrit :
> 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 <[email protected]>
> ---
> 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);
> + }
Please, look at ip6_rt_put(), it is explicitly stated that it can be called with
rt == NULL.

2019-07-27 20:28:27

by David Miller

Subject: Re: [PATCH 2/2] net: ipv6: Fix a possible null-pointer dereference in vti6_link_config()

From: Jia-Ju Bai <[email protected]>
Date: Fri, 26 Jul 2019 16:03:21 +0800

> @@ -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);
> + }

ip6_rt_put() can take a NULL argument without any problem.

I want to make it clear that because of mistakes of this nature, and
how frequently you make them, it is very tiring and exhausting to
review your changes...