Re: [PATCH] netfilter: nf_tables: handle more than 8 * PAGE_SIZE set name allocations

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

On Fri, Mar 07, 2014 at 12:34:05PM +0100, Patrick McHardy wrote:
> We currently have a limit of 8 * PAGE_SIZE anonymous sets. Lift that limit
> by continuing the scan if the entire page is exhausted.
> 
> Signed-off-by: Patrick McHardy <kaber@trash.net>
> ---
>  net/netfilter/nf_tables_api.c | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
> index f25d011..89d7ec4 100644
> --- a/net/netfilter/nf_tables_api.c
> +++ b/net/netfilter/nf_tables_api.c
> @@ -2004,7 +2004,7 @@ static int nf_tables_set_alloc_name(struct nft_ctx *ctx, struct nft_set *set,
>  	const struct nft_set *i;
>  	const char *p;
>  	unsigned long *inuse;
> -	unsigned int n = 0;
> +	unsigned int n = 0, min = 0;
>  
>  	p = strnchr(name, IFNAMSIZ, '%');
>  	if (p != NULL) {
> @@ -2014,23 +2014,28 @@ static int nf_tables_set_alloc_name(struct nft_ctx *ctx, struct nft_set *set,
>  		inuse = (unsigned long *)get_zeroed_page(GFP_KERNEL);
>  		if (inuse == NULL)
>  			return -ENOMEM;
> -
> +cont:
>  		list_for_each_entry(i, &ctx->table->sets, list) {
>  			int tmp;
>  
>  			if (!sscanf(i->name, name, &tmp))
>  				continue;
> -			if (tmp < 0 || tmp >= BITS_PER_BYTE * PAGE_SIZE)
> +			if (tmp < min || tmp >= min + BITS_PER_BYTE * PAGE_SIZE)

I think we can break looping if tmp >= min + BITS_PER_BYTE * PAGE_SIZE
fulfills (assuming the list of sets is ordered).

>  				continue;
>  
> -			set_bit(tmp, inuse);
> +			set_bit(tmp - min, inuse);
>  		}
>  
>  		n = find_first_zero_bit(inuse, BITS_PER_BYTE * PAGE_SIZE);
> +		if (n >= BITS_PER_BYTE * PAGE_SIZE) {
> +			min += BITS_PER_BYTE * PAGE_SIZE;
> +			memset(inuse, 0, PAGE_SIZE);
> +			goto cont;

If the page is full, we start iterating over the set list from the
beginning.

> +		}
>  		free_page((unsigned long)inuse);
>  	}
>  
> -	snprintf(set->name, sizeof(set->name), name, n);
> +	snprintf(set->name, sizeof(set->name), name, min + n);
>  	list_for_each_entry(i, &ctx->table->sets, list) {
>  		if (!strcmp(set->name, i->name))
>  			return -ENFILE;
> -- 
> 1.8.5.3
>