Re: [PATCH] selftests/mm: use calloc instead of malloc in pagemap_ioctl.c

[Donet Tom <donettom@linux.ibm.com>]

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On 8/25/25 10:36 PM, I Viswanath wrote:
> As per Documentation/process/deprecated.rst, dynamic size calculations
> should not be performed in memory allocator arguments due to possible
> overflows.
>
> Replaced malloc with calloc to avoid open-ended arithmetic
> and prevent possible overflows.
>
> Signed-off-by: I Viswanath<viswanathiyyappan@gmail.com>


LGTM

Reviewed by: Donet Tom <donettom@linux.ibm.com>


> ---
> Even though the arguments are small enough an overflow cannot happen,
> I think it's still better to follow kernel standard practices.
>
>   tools/testing/selftests/mm/pagemap_ioctl.c | 24 +++++++++++-----------
>   1 file changed, 12 insertions(+), 12 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/pagemap_ioctl.c b/tools/testing/selftests/mm/pagemap_ioctl.c
> index 0d4209eef0c3..4e6b815e96b2 100644
> --- a/tools/testing/selftests/mm/pagemap_ioctl.c
> +++ b/tools/testing/selftests/mm/pagemap_ioctl.c
> @@ -209,7 +209,7 @@ int userfaultfd_tests(void)
>   	wp_addr_range(mem, mem_size);
>   
>   	vec_size = mem_size/page_size;
> -	vec = malloc(sizeof(struct page_region) * vec_size);
> +	vec = calloc(vec_size, sizeof(struct page_region));
>   
>   	written = pagemap_ioctl(mem, mem_size, vec, 1, PM_SCAN_WP_MATCHING | PM_SCAN_CHECK_WPASYNC,
>   				vec_size - 2, PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN);
> @@ -247,11 +247,11 @@ int sanity_tests_sd(void)
>   	vec_size = num_pages/2;
>   	mem_size = num_pages * page_size;
>   
> -	vec = malloc(sizeof(struct page_region) * vec_size);
> +	vec = calloc(vec_size, sizeof(struct page_region));
>   	if (!vec)
>   		ksft_exit_fail_msg("error nomem\n");
>   
> -	vec2 = malloc(sizeof(struct page_region) * vec_size);
> +	vec2 = calloc(vec_size, sizeof(struct page_region));
>   	if (!vec2)
>   		ksft_exit_fail_msg("error nomem\n");
>   
> @@ -436,7 +436,7 @@ int sanity_tests_sd(void)
>   	mem_size = 1050 * page_size;
>   	vec_size = mem_size/(page_size*2);
>   
> -	vec = malloc(sizeof(struct page_region) * vec_size);
> +	vec = calloc(vec_size, sizeof(struct page_region));
>   	if (!vec)
>   		ksft_exit_fail_msg("error nomem\n");
>   
> @@ -491,7 +491,7 @@ int sanity_tests_sd(void)
>   	mem_size = 10000 * page_size;
>   	vec_size = 50;
>   
> -	vec = malloc(sizeof(struct page_region) * vec_size);
> +	vec = calloc(vec_size, sizeof(struct page_region));
>   	if (!vec)
>   		ksft_exit_fail_msg("error nomem\n");
>   
> @@ -541,7 +541,7 @@ int sanity_tests_sd(void)
>   	vec_size = 1000;
>   	mem_size = vec_size * page_size;
>   
> -	vec = malloc(sizeof(struct page_region) * vec_size);
> +	vec = calloc(vec_size, sizeof(struct page_region));
>   	if (!vec)
>   		ksft_exit_fail_msg("error nomem\n");
>   
> @@ -695,8 +695,8 @@ int base_tests(char *prefix, char *mem, unsigned long long mem_size, int skip)
>   	}
>   
>   	vec_size = mem_size/page_size;
> -	vec = malloc(sizeof(struct page_region) * vec_size);
> -	vec2 = malloc(sizeof(struct page_region) * vec_size);
> +	vec = calloc(vec_size, sizeof(struct page_region));
> +	vec2 = calloc(vec_size, sizeof(struct page_region));
>   
>   	/* 1. all new pages must be not be written (dirty) */
>   	written = pagemap_ioctl(mem, mem_size, vec, 1, PM_SCAN_WP_MATCHING | PM_SCAN_CHECK_WPASYNC,
> @@ -807,8 +807,8 @@ int hpage_unit_tests(void)
>   	unsigned long long vec_size = map_size/page_size;
>   	struct page_region *vec, *vec2;
>   
> -	vec = malloc(sizeof(struct page_region) * vec_size);
> -	vec2 = malloc(sizeof(struct page_region) * vec_size);
> +	vec = calloc(vec_size, sizeof(struct page_region));
> +	vec2 = calloc(vec_size, sizeof(struct page_region));
>   	if (!vec || !vec2)
>   		ksft_exit_fail_msg("malloc failed\n");
>   
> @@ -997,7 +997,7 @@ int unmapped_region_tests(void)
>   	void *start = (void *)0x10000000;
>   	int written, len = 0x00040000;
>   	long vec_size = len / page_size;
> -	struct page_region *vec = malloc(sizeof(struct page_region) * vec_size);
> +	struct page_region *vec = calloc(vec_size, sizeof(struct page_region));
>   
>   	/* 1. Get written pages */
>   	written = pagemap_ioctl(start, len, vec, vec_size, 0, 0,
> @@ -1062,7 +1062,7 @@ int sanity_tests(void)
>   	mem_size = 10 * page_size;
>   	vec_size = mem_size / page_size;
>   
> -	vec = malloc(sizeof(struct page_region) * vec_size);
> +	vec = calloc(vec_size, sizeof(struct page_region));
>   	mem = mmap(NULL, mem_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
>   	if (mem == MAP_FAILED || vec == MAP_FAILED)
>   		ksft_exit_fail_msg("error nomem\n");

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