Re: [libnftnl PATCH 2/7] ruleset: Prevent memleak in nftnl_ruleset_snprintf_*() functions

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

On Fri, Aug 12, 2016 at 01:33:34AM +0200, Phil Sutter wrote:
> From: Phil Sutter <psutter@redhat.com>
> 
> This is an ugly aspect of the SNPRINTF_BUFFER_SIZE() macro: it contains
> a return statement and if that triggers, the function returns without
> freeing the iterator object. Therefore duplicate the 'ret < 0' check
> before calling it, freeing the iterator knowing that we will bail out
> immediately afterwards anyway.
> 
> Cc: Arturo Borrero <arturo.borrero.glez@gmail.com>
> Signed-off-by: Phil Sutter <phil@nwl.cc>
> ---
>  src/ruleset.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/src/ruleset.c b/src/ruleset.c
> index 666bcc7a246b6..93cf95ab61e15 100644
> --- a/src/ruleset.c
> +++ b/src/ruleset.c
> @@ -888,12 +888,16 @@ nftnl_ruleset_snprintf_table(char *buf, size_t size,
>  	t = nftnl_table_list_iter_next(ti);
>  	while (t != NULL) {
>  		ret = nftnl_table_snprintf(buf+offset, len, t, type, flags);
> +		if (ret < 0)
> +			nftnl_table_list_iter_destroy(ti);
>  		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);

Better get rid of the obscure if (ret < 0) hidden in
SNPRINT_BUFFER_SIZE.

Or simply set:

        if (ret < 0)
                ret = 0;

in SNPRINT_BUFFER_SIZE.