Re: [PATCH net] netfilter: xt_hashlimit: do not allow empty names

[Eric Dumazet]

On Sun, 2018-01-28 at 07:41 -0800, Eric Dumazet wrote:
> From: Eric Dumazet <eduma...@google.com>
> 
> Syzbot reported a WARN() in proc_create_data() [1]
> 
> Issue here is that xt_hashlimit does not check that user space provided
> an empty table name.

> Signed-off-by: Eric Dumazet <eduma...@google.com>
> Reported-by: syzbot <syzkal...@googlegroups.com>
> ---
>  net/netfilter/xt_hashlimit.c |    2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/net/netfilter/xt_hashlimit.c b/net/netfilter/xt_hashlimit.c
> index 
> 5da8746f7b88ff4c9446f256e542e823a6a561b0..eae732e013df92a364b500645360d4606c283a75
>  100644
> --- a/net/netfilter/xt_hashlimit.c
> +++ b/net/netfilter/xt_hashlimit.c
> @@ -894,6 +894,8 @@ static int hashlimit_mt_check_common(const struct 
> xt_mtchk_param *par,
>                       return -ERANGE;
>       }
>  
> +     if (!name[0])
> +             return -EINVAL;
>       mutex_lock(&hashlimit_mutex);
>       *hinfo = htable_find_get(net, name, par->family);
>       if (*hinfo == NULL) {

I wonder if we should also check if name includes a '/' ?

if (!name[0] || strchr(name, '/'))
    return -EINVAL;