linux-kernel - Re: [RFC] netfilter: cttimeout: remove VLA in ctnl_timeout_parse

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Date:   Sun, 11 Mar 2018 23:04:14 +0100
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
        Florian Westphal <fw@...len.de>,
        "David S. Miller" <davem@...emloft.net>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <garsilva@...eddedor.com>
Subject: Re: [RFC] netfilter: cttimeout: remove VLA in
 ctnl_timeout_parse_policy

On Tue, Mar 06, 2018 at 12:47:55PM -0600, Gustavo A. R. Silva wrote:
> In preparation to enabling -Wvla, remove VLA and replace it
> with dynamic memory allocation.

Looks good but...

> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
> ---
>  net/netfilter/nfnetlink_cttimeout.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/net/netfilter/nfnetlink_cttimeout.c b/net/netfilter/nfnetlink_cttimeout.c
> index 95b0470..a2f7d92 100644
> --- a/net/netfilter/nfnetlink_cttimeout.c
> +++ b/net/netfilter/nfnetlink_cttimeout.c
> @@ -52,18 +52,26 @@ ctnl_timeout_parse_policy(void *timeouts,
>  			  struct net *net, const struct nlattr *attr)
>  {
>  	int ret = 0;
> +	struct nlattr **tb = NULL;

I think we don't need to initialize this, right?

>  
>  	if (likely(l4proto->ctnl_timeout.nlattr_to_obj)) {
> -		struct nlattr *tb[l4proto->ctnl_timeout.nlattr_max+1];
> +		tb = kcalloc(l4proto->ctnl_timeout.nlattr_max + 1, sizeof(*tb),
> +			     GFP_KERNEL);
> +
> +		if (!tb)
> +			return -ENOMEM;
>  
>  		ret = nla_parse_nested(tb, l4proto->ctnl_timeout.nlattr_max,
>  				       attr, l4proto->ctnl_timeout.nla_policy,
>  				       NULL);
>  		if (ret < 0)
> -			return ret;
> +			goto err;
>  
>  		ret = l4proto->ctnl_timeout.nlattr_to_obj(tb, net, timeouts);
>  	}
> +
> +err:
> +	kfree(tb);
>  	return ret;
>  }
>  
> -- 
> 2.7.4
>