Re: [PATCH 05/10] cmdline: fix port list parsing

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

On Thu, Jun 19, 2025 at 09:10:31AM +0200, David Marchand wrote:
> Doing arithmetics with the NULL pointer is undefined.
> 
> Caught by UBSan:
> 
> ../lib/cmdline/cmdline_parse_portlist.c:40:19: runtime error:
> 	applying non-zero offset 1 to null pointer
> SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior
> 	../lib/cmdline/cmdline_parse_portlist.c:40:19 in
> 
> Fixes: af75078fece3 ("first public release")
> Cc: stable@dpdk.org
> 
> Signed-off-by: David Marchand <david.marchand@redhat.com>
> ---
>  lib/cmdline/cmdline_parse_portlist.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/lib/cmdline/cmdline_parse_portlist.c b/lib/cmdline/cmdline_parse_portlist.c
> index ef6ce223b5..0c07cc02b5 100644
> --- a/lib/cmdline/cmdline_parse_portlist.c
> +++ b/lib/cmdline/cmdline_parse_portlist.c
> @@ -4,6 +4,7 @@
>   * All rights reserved.
>   */
>  
> +#include <stdbool.h>
>  #include <stdio.h>
>  #include <stdlib.h>
>  #include <string.h>
> @@ -37,10 +38,11 @@ parse_ports(cmdline_portlist_t *pl, const char *str)
>  	const char *first, *last;
>  	char *end;
>  
> -	for (first = str, last = first;
> -	    first != NULL && last != NULL;
> -	    first = last + 1) {

Maybe I'm a little slow this morning, but I can't see how this is actually
a problem. By my understanding, the check for "first != NULL && last !=
NULL" happens before any increment of "first = last + 1", meaning we are
guaranteed that the last is never null when we increment it.

/Bruce

> +	if (str == NULL)
> +		return 0;
>  
> +	last = first = str;
> +	do {
>  		last = strchr(first, ',');
>  
>  		errno = 0;
> @@ -65,7 +67,10 @@ parse_ports(cmdline_portlist_t *pl, const char *str)
>  			return -1;
>  
>  		parse_set_list(pl, ps, pe);
> -	}
> +		if (last == NULL)
> +			break;
> +		first = last + 1;
> +	} while (true);
>  
>  	return 0;
>  }
> -- 
> 2.49.0
>