On Mon, 2017-02-27 at 11:07 -0800, Cong Wang wrote:
> Andrey reported a NULL pointer deref bug in ipv6_route_ioctl()
> -> ip6_route_del() -> __ip6_del_rt_siblings() code path. This is
> because ip6_null_entry is returned in this path since ip6_null_entry
> is kinda default for a ipv6 route table root node. Quote from
> David Ahern:
>
> ip6_null_entry is the root of all ipv6 fib tables making it integrated
> into the table ...
>
> We should ignore any attempt of trying to delete it, like we do in
> __ip6_del_rt() path and several others.
>
> Reported-by: Andrey Konovalov <andreyk...@google.com>
> Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
> ---
> net/ipv6/route.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index f54f426..9da77e9 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -2169,10 +2169,13 @@ int ip6_del_rt(struct rt6_info *rt)
> static int __ip6_del_rt_siblings(struct rt6_info *rt, struct fib6_config
> *cfg)
> {
> struct nl_info *info = &cfg->fc_nlinfo;
> + struct net *net = info->nl_net;
> struct sk_buff *skb = NULL;
> struct fib6_table *table;
> int err;
>
> + if (rt == net->ipv6.ip6_null_entry)
> + return -ENOENT;
It looks the caller did a dst_hold(&rt->dst);
So this new error path would leave a refcount leak.
Note that I was not able to trigger the crash on old kernels, so it
would be nice to get a precise idea of bug origin.
Thanks.
