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

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Message-Id: <20251222180509.b12684e112195ac3f7ee9389@linux-foundation.org>
Date: Mon, 22 Dec 2025 18:05:09 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Li Wang <liwang@...hat.com>
Cc: David Laight <david.laight.linux@...il.com>,
 linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, David Hildenbrand <david@...nel.org>, Mark Brown
 <broonie@...nel.org>, Shuah Khan <shuah@...nel.org>, Waiman Long
 <longman@...hat.com>
Subject: Re: [PATCH v3 1/3] selftests/mm/write_to_hugetlbfs: parse -s as
 size_t

On Mon, 22 Dec 2025 18:56:49 +0800 Li Wang <liwang@...hat.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?