Re: [PATCH] selftests/powerpc: Fix strncpy usage

Le 22/06/2018 à 16:43, Breno Leitao a écrit :

Hi Segher,

On 06/21/2018 08:18 PM, Segher Boessenkool wrote:

quoted

On Wed, Jun 20, 2018 at 07:51:11PM -0300, Breno Leitao wrote:

quoted

-	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