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

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

[I Viswanath]

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>
---
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");
-- 
2.50.1

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

[Vishal Moola (Oracle)]

On Mon, Aug 25, 2025 at 10:36:43PM +0530, 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: Vishal Moola (Oracle) <vishal.moola@gmail.com>

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

[David Hildenbrand]

On 25.08.25 19:06, 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>

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Cheers

David / dhildenb