Re: [PATCH v3 1/3] selftests/mm/write_to_hugetlbfs: parse -s as size_t

Andrew Morton
2025-12-23T02:05:14Z

On Mon, 22 Dec 2025 18:56:49 +0800 Li Wang <liwang@redhat.com> wrote:

> > It reality scanf() is 'not the function you are lookign for'.
> >
> > IIRC the 'SUS' (used to) say that this was absolutely fine for command
> > line parsing for 'standard utilities'.
> >
> > It is best to use strtoul() and check the 'end' character is '\0'.
>
> Hmm, that sounds like we need to go back to the patch V1 [1] method.
> But I am not sure, @Andrew Morton, do you think so?
>
> --- a/tools/testing/selftests/mm/write_to_hugetlbfs.c
> +++ b/tools/testing/selftests/mm/write_to_hugetlbfs.c
> @@ -86,10 +86,17 @@ int main(int argc, char **argv)
> while ((c = getopt(argc, argv, "s:p:m:owlrn")) != -1) {
> switch (c) {
> case 's':
> - if (sscanf(optarg, "%zu", &size) != 1) {
> - perror("Invalid -s.");
> + char *end = NULL;
> + unsigned long tmp = strtoul(optarg, &end, 10);
> + if (errno || end == optarg || *end != '\0') {
> + perror("Invalid -s size");
> exit_usage();
> }
> + if (tmp == 0) {
> + perror("size not found");
> + exit_usage();
> + }
> + size = (size_t)tmp;
> break;
> case 'p':

Geeze guys, it's just a selftest.

hp2:/usr/src/linux-6.19-rc1> grep -r scanf tools/testing/selftests | wc -l
177

if your command line breaks the selftest, fix your command line?