[PATCH] selftests/powerpc: Fix strncpy usage

[Christophe LEROY]

Le 22/06/2018 à 16:43, Breno Leitao a écrit :
> Hi Segher,
> 
> On 06/21/2018 08:18 PM, Segher Boessenkool wrote:
>> On Wed, Jun 20, 2018 at 07:51:11PM -0300, Breno Leitao wrote:
>>> -	strncpy(prog, argv[0], strlen(argv[0]));
>>> +	strncpy(prog, argv[0], sizeof(prog) - 1);
>>
>> 	strncpy(prog, argv[0], sizeof prog);
>> 	if (prog[sizeof prog - 1])
>> 		scream_bloody_murder();
>>
>> Silently using the wrong data is a worse habit than not checking for
>> overflows ;-)
> 
> Completely agree! Thanks for bringing this up.
> 
> If you don't mind, I would solve this problem slightly different, as it seems
> to be more readable.
> 
> 
> -       strncpy(prog, argv[0], strlen(argv[0]));
> +       if (strlen(argv[0]) >= LEN_MAX){

wouldn't it be better to use sizeof(prog) instead of LEN_MAX ?

> +               fprintf(stderr, "Very big executable name: %s\n", argv[0]);
> +               return 1;
> +       }
> +
> +       strncpy(prog, argv[0], sizeof(prog) - 1);

You have checked before that argv[0] is not too long, so you should not 
need to use strncpy(), strcpy() would do it.

>          return test_harness(dscr_inherit_exec, "dscr_inherit_exec_test");
> 

Christophe