Re: [dpdk-stable] [PATCH v2] lib/cfgfile: replace strcat with strlcat

[Bruce Richardson <bruce.richardson@intel.com>]

On Fri, Mar 08, 2019 at 12:45:50PM +0000, Chaitanya Babu Talluri wrote:
> Replace strcat with strlcat to avoid buffer overflow.
> 
> Fixes: a6a47ac9c2 ("cfgfile: rework load function")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Chaitanya Babu Talluri <tallurix.chaitanya.babu@intel.com>
> ---
> v2: Instead of strcat, used strlcat.
> ---
>  lib/librte_cfgfile/rte_cfgfile.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/librte_cfgfile/rte_cfgfile.c b/lib/librte_cfgfile/rte_cfgfile.c
> index 7d8c941ea..3296bb6f8 100644
> --- a/lib/librte_cfgfile/rte_cfgfile.c
> +++ b/lib/librte_cfgfile/rte_cfgfile.c
> @@ -8,6 +8,7 @@
>  #include <ctype.h>
>  #include <errno.h>
>  #include <rte_common.h>
> +#include <rte_string_fns.h>
>  
>  #include "rte_cfgfile.h"
>  
> @@ -224,10 +225,11 @@ rte_cfgfile_load_with_params(const char *filename, int flags,
>  			_strip(split[1], strlen(split[1]));
>  			char *end = memchr(split[1], '\\', strlen(split[1]));
>  
> +			size_t split_len = strlen(split[1]) + 1;
>  			while (end != NULL) {
>  				if (*(end+1) == params->comment_character) {
>  					*end = '\0';
> -					strcat(split[1], end+1);
> +					strlcat(split[1], end+1, split_len);

I don't think this will do what you want. Remember that strlcat takes the
total length of the buffer, which means that if split_len is set to the
current length (as you do before the while statement), then passing that
as the length parameter will cause strlcat to do nothing, since it sees the
buffer as already full.

/Bruce