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

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Date:   Sun, 28 Jan 2018 09:54:05 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>
Cc:     Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
        Florian Westphal <fw@...len.de>,
        netfilter-devel@...r.kernel.org, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net] netfilter: xt_hashlimit: do not allow empty names

On Sun, 2018-01-28 at 07:41 -0800, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.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 <edumazet@...gle.com>
> Reported-by: syzbot <syzkaller@...glegroups.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;