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

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Message-ID: <39c9af10-d66f-4bcc-93a6-9e2d33827938@redhat.com>
Date: Sun, 21 Dec 2025 15:23:22 -0500
From: Waiman Long <llong@...hat.com>
To: Li Wang <liwang@...hat.com>, akpm@...ux-foundation.org,
 linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org
Cc: David Hildenbrand <david@...nel.org>, Mark Brown <broonie@...nel.org>,
 Shuah Khan <shuah@...nel.org>
Subject: Re: [PATCH v3 1/3] selftests/mm/write_to_hugetlbfs: parse -s as
 size_t

On 12/21/25 7:26 AM, Li Wang wrote:
> write_to_hugetlbfs currently parses the -s size argument with atoi()
> into an int. This silently accepts malformed input, cannot report overflow,
> and can truncate large sizes.
>
> --- Error log ---
>   # uname -r
>   6.12.0-xxx.el10.aarch64+64k
>
>   # ls /sys/kernel/mm/hugepages/hugepages-*
>   hugepages-16777216kB/  hugepages-2048kB/  hugepages-524288kB/
>
>   #./charge_reserved_hugetlb.sh -cgroup-v2
>   # -----------------------------------------
>   ...
>   # nr hugepages = 10
>   # writing cgroup limit: 5368709120
>   # writing reseravation limit: 5368709120
>   ...
>   # Writing to this path: /mnt/huge/test
>   # Writing this size: -1610612736        <--------
>
> Switch the size variable to size_t and parse -s with sscanf("%zu", ...).
> Also print the size using %zu.
>
> This avoids incorrect behavior with large -s values and makes the utility
> more robust.
>
> Signed-off-by: Li Wang <liwang@...hat.com>
> Cc: David Hildenbrand <david@...nel.org>
> Cc: Mark Brown <broonie@...nel.org>
> Cc: Shuah Khan <shuah@...nel.org>
> Cc: Waiman Long <longman@...hat.com>
> Acked-by: David Hildenbrand (Red Hat) <david@...nel.org>
> ---
>   tools/testing/selftests/mm/write_to_hugetlbfs.c | 9 ++++++---
>   1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/write_to_hugetlbfs.c b/tools/testing/selftests/mm/write_to_hugetlbfs.c
> index 34c91f7e6128..ecb5f7619960 100644
> --- a/tools/testing/selftests/mm/write_to_hugetlbfs.c
> +++ b/tools/testing/selftests/mm/write_to_hugetlbfs.c
> @@ -68,7 +68,7 @@ int main(int argc, char **argv)
>   	int key = 0;
>   	int *ptr = NULL;
>   	int c = 0;
> -	int size = 0;
> +	size_t size = 0;
>   	char path[256] = "";
>   	enum method method = MAX_METHOD;
>   	int want_sleep = 0, private = 0;
> @@ -86,7 +86,10 @@ int main(int argc, char **argv)
>   	while ((c = getopt(argc, argv, "s:p:m:owlrn")) != -1) {
>   		switch (c) {
>   		case 's':
> -			size = atoi(optarg);
> +			if (sscanf(optarg, "%zu", &size) != 1) {
> +				perror("Invalid -s.");
> +				exit_usage();
> +			}
>   			break;
>   		case 'p':
>   			strncpy(path, optarg, sizeof(path) - 1);
> @@ -131,7 +134,7 @@ int main(int argc, char **argv)
>   	}
>   
>   	if (size != 0) {
> -		printf("Writing this size: %d\n", size);
> +		printf("Writing this size: %zu\n", size);
>   	} else {
>   		errno = EINVAL;
>   		perror("size not found");

LGTM

Acked-by: Waiman Long <longman@...hat.com>