netdev - Re: [PATCH] netfilter: properly initialize xt_table

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Date:   Thu, 17 May 2018 10:59:51 +0200
From:   Michal Kubecek <mkubecek@...e.cz>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
        Florian Westphal <fw@...len.de>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH] netfilter: properly initialize xt_table_info structure

On Thu, May 17, 2018 at 10:44:42AM +0200, Greg Kroah-Hartman wrote:
> When allocating a xt_table_info structure, we should be clearing out the
> full amount of memory that was allocated, not just the "header" of the
> structure.  Otherwise odd values could be passed to userspace, which is
> not a good thing.
> 
> Cc: stable <stable@...r.kernel.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> ---
>  net/netfilter/x_tables.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
> index cb7cb300c3bc..a300e8252bb6 100644
> --- a/net/netfilter/x_tables.c
> +++ b/net/netfilter/x_tables.c
> @@ -1187,7 +1187,7 @@ struct xt_table_info *xt_alloc_table_info(unsigned int size)
>  	if (!info)
>  		return NULL;
>  
> -	memset(info, 0, sizeof(*info));
> +	memset(info, 0, sz);
>  	info->size = size;
>  	return info;
>  }
> -- 
> 2.17.0
> 

Or we can replace kvmalloc() by kvzalloc() and remove the memset().

Michal Kubecek