Re: [PATCH nf-next 1/2] netfilter: nf_tables: Check chain's use count before alloc new handle in nf_tables_newrule

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Thu, Dec 29, 2016 at 11:39:28AM +0800, fgao@ikuai8.com wrote:
> From: Gao Feng <fgao@ikuai8.com>
> 
> Although current nf_tables_alloc_handle doesn't allocate any actual
> resource, but it should check invalid condition before allocation in
> logic.
> 
> Signed-off-by: Gao Feng <fgao@ikuai8.com>
> ---
>  net/netfilter/nf_tables_api.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
> index a019a87..ecc516c 100644
> --- a/net/netfilter/nf_tables_api.c
> +++ b/net/netfilter/nf_tables_api.c
> @@ -2175,10 +2175,10 @@ static int nf_tables_newrule(struct net *net, struct sock *nlsk,
>  	} else {
>  		if (!create || nlh->nlmsg_flags & NLM_F_REPLACE)
>  			return -EINVAL;
> -		handle = nf_tables_alloc_handle(table);
> -
>  		if (chain->use == UINT_MAX)
>  			return -EOVERFLOW;
> +
> +		handle = nf_tables_alloc_handle(table);

NFTA_RULE_POSITION below may also fail, so the handle becomes unused
there too. I think it's not worth trying given that this may only
happen if we hit a crazy number of rules.