[PATCH] selftests/powerpc: Fix strncpy usage

[Breno Leitao]

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