netdev - Re: [PATCH nf-next] netfilter: log: Check param to avoid overflow in nf_log

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Date:   Mon, 29 Aug 2016 11:55:25 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     fgao@...ai8.com
Cc:     kaber@...sh.net, davem@...emloft.net,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org, gfree.wind@...il.com
Subject: Re: [PATCH nf-next] netfilter: log: Check param to avoid overflow in
 nf_log_set

On Sun, Aug 28, 2016 at 10:30:18PM +0800, fgao@...ai8.com wrote:
> From: Gao Feng <fgao@...ai8.com>
> 
> The nf_log_set is an interface function, so it should do the strict sanity
> check of parameters. Add  one sanity check for pf, it could not exceed
> NFPROTO_NUMPROTO, and print error log when pf is invalid.
> 
> Signed-off-by: Gao Feng <fgao@...ai8.com>
> ---
>  net/netfilter/nf_log.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/net/netfilter/nf_log.c b/net/netfilter/nf_log.c
> index aa5847a..02ce0b9 100644
> --- a/net/netfilter/nf_log.c
> +++ b/net/netfilter/nf_log.c
> @@ -43,8 +43,10 @@ void nf_log_set(struct net *net, u_int8_t pf, const struct nf_logger *logger)
>  {
>  	const struct nf_logger *log;
>  
> -	if (pf == NFPROTO_UNSPEC)
> +	if (pf == NFPROTO_UNSPEC || pf >= NFPROTO_NUMPROTO) {
> +		pr_err("Wrong pf(%d) for nf log", pf);
>  		return;

I'd suggest you change this function nf_log_set() to:

        int nf_log_set(struct net *net, ...)

And update the callsites.

Then, you can simply return -EOPNOTSUPP instead and remove that
pr_err() message. This message is very unlikely to be displayed.

Thanks!