[Devel] Re: [PATCH] iptables compat code error way & module refcounting fix

[Patrick McHardy]

Dmitry Mishin wrote:
> This patch fixes bug in iptables modules refcounting on compat error way.
> 
> As we are getting modules in check_compat_entry_size_and_hooks(), in case of
> later error, we should put them all in translate_compat_table(), not  in the
> compat_copy_entry_from_user() or compat_copy_match_from_user(), as it is now.
> 
> Signed-off-by: Dmitry Mishin <dim at openvz.org>
> Acked-by: Vasily Averin <vvs at openvz.org>
> Acked-by: Kirill Korotaev <dev at openvz.org>
> 
>  ip_tables.c |   36 +++++++++++-------------------------
>  1 file changed, 11 insertions(+), 25 deletions(-)
> 
> ----
> @@ -1618,7 +1603,7 @@ translate_compat_table(const char *name,
>  		unsigned int *hook_entries,
>  		unsigned int *underflows)
>  {
> -	unsigned int i;
> +	unsigned int i, j;
>  	struct xt_table_info *newinfo, *info;
>  	void *pos, *entry0, *entry1;
>  	unsigned int size;
> @@ -1636,21 +1621,21 @@ translate_compat_table(const char *name,
>  	}
>  
>  	duprintf("translate_compat_table: size %u\n", info->size);
> -	i = 0;
> +	j = 0;
>  	xt_compat_lock(AF_INET);
>  	/* Walk through entries, checking offsets. */
>  	ret = IPT_ENTRY_ITERATE(entry0, total_size,
>  				check_compat_entry_size_and_hooks,
>  				info, &size, entry0,
>  				entry0 + total_size,
> -				hook_entries, underflows, &i, name);
> +				hook_entries, underflows, &j, name);
>  	if (ret != 0)
>  		goto out_unlock;
>  
>  	ret = -EINVAL;
> -	if (i != number) {
> +	if (j != number) {
>  		duprintf("translate_compat_table: %u not %u entries\n",
> -			 i, number);
> +			 j, number);
>  		goto out_unlock;
>  	}
>  
> @@ -1709,6 +1694,7 @@ translate_compat_table(const char *name,
>  free_newinfo:
>  	xt_free_table_info(newinfo);
>  out:
> +	IPT_ENTRY_ITERATE(entry0, total_size, cleanup_entry, &j);
>  	return ret;
>  out_unlock:
>  	xt_compat_unlock(AF_INET);
> 

This doesn't look right, if we fail at xt_alloc_table_info for
example the module references are not released. What case
exactly is this patch supposed to fix?