netdev - Re: [PATCH 03/12] netfilter: ebtables: don't attempt to allocate 0-sized compat array

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Date:   Tue, 24 Apr 2018 11:55:24 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>,
        netfilter-devel@...r.kernel.org
Cc:     davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH 03/12] netfilter: ebtables: don't attempt to allocate
 0-sized compat array

Hello!

On 4/23/2018 8:57 PM, Pablo Neira Ayuso wrote:

> From: Florian Westphal <fw@...len.de>
> 
> Dmitry reports 32bit ebtables on 64bit kernel got broken by
> a recent change that returns -EINVAL when ruleset has no entries.
> 
> ebtables however only counts user-defined chains, so for the
> initial table nentries will be 0.
> 
> Don't try to allocate the compat array in this case, as no user

    As if, perhaps?

> defined rules exist no rule will need 64bit translation.
> 
> Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
> Fixes: 7d7d7e02111e9 ("netfilter: compat: reject huge allocation requests")
> Signed-off-by: Florian Westphal <fw@...len.de>
> Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
> ---
>   net/bridge/netfilter/ebtables.c | 11 ++++++-----
>   1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
> index 032e0fe45940..28a4c3490359 100644
> --- a/net/bridge/netfilter/ebtables.c
> +++ b/net/bridge/netfilter/ebtables.c
> @@ -1825,13 +1825,14 @@ static int compat_table_info(const struct ebt_table_info *info,
>   {
>   	unsigned int size = info->entries_size;
>   	const void *entries = info->entries;
> -	int ret;
>   
>   	newinfo->entries_size = size;
> -
> -	ret = xt_compat_init_offsets(NFPROTO_BRIDGE, info->nentries);
> -	if (ret)
> -		return ret;
> +	if (info->nentries) {
> +		int ret = xt_compat_init_offsets(NFPROTO_BRIDGE,
> +						 info->nentries);

    Need an empty line here...

> +		if (ret)
> +			return ret;
> +	}
>   
>   	return EBT_ENTRY_ITERATE(entries, size, compat_calc_entry, info,
>   							entries, newinfo);

MBR, Sergei