[PATCH] selftests/mm/mseal_test: Fix mmap return value check in test_seal_zero_address

[PATCH] selftests/mm/mseal_test: Fix mmap return value check in test_seal_zero_address

[longlong yan]

test_seal_zero_address() uses mmap() with MAP_FIXED to map at address 0,
but only checks if the return value equals 0. If mmap() fails, it returns
MAP_FAILED ((void *)-1), not 0. The existing check FAIL_TEST_IF_FALSE(ptr == 0)
would pass when ptr == -1 (since -1 != 0 is true), causing the test to
continue with an invalid pointer.

Add a check for MAP_FAILED before verifying ptr == 0, consistent with all
other mmap() checks in this file which use FAIL_TEST_IF_FALSE(ptr != (void *)-1).

Fixes: 4926c7a52de7 ("selftest mm/mseal memory sealing")
Signed-off-by: longlong yan <yanlonglong@kylinos.cn>
---
 tools/testing/selftests/mm/mseal_test.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/mm/mseal_test.c b/tools/testing/selftests/mm/mseal_test.c
index faad4833366a..a6ecc81c6aa0 100644
--- a/tools/testing/selftests/mm/mseal_test.c
+++ b/tools/testing/selftests/mm/mseal_test.c
@@ -482,7 +482,7 @@ static void test_seal_zero_address(void)
 	/* use mmap to change protection. */
 	ptr = mmap(0, size, PROT_NONE,
 		   MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0);
-	FAIL_TEST_IF_FALSE(ptr == 0);
+	FAIL_TEST_IF_FALSE(ptr == (void *)-1);
 
 	size = get_vma_size(ptr, &prot);
 	FAIL_TEST_IF_FALSE(size == 4 * page_size);
-- 
2.43.0

Re: [PATCH] selftests/mm/mseal_test: Fix mmap return value check in test_seal_zero_address

[Mike Rapoport]

Hi,

On Mon, Jul 06, 2026 at 04:30:48PM +0800, longlong yan wrote:
> test_seal_zero_address() uses mmap() with MAP_FIXED to map at address 0,
> but only checks if the return value equals 0. If mmap() fails, it returns
> MAP_FAILED ((void *)-1), not 0. The existing check FAIL_TEST_IF_FALSE(ptr == 0)
> would pass when ptr == -1 (since -1 != 0 is true), causing the test to
> continue with an invalid pointer.
 
> Add a check for MAP_FAILED before verifying ptr == 0, consistent with all
> other mmap() checks in this file which use FAIL_TEST_IF_FALSE(ptr != (void *)-1).

The changelog looks like an LLM generated. Can you please instruct your LLM
to produce more concise descriptions that communicated the gist of the
change?
 
> Fixes: 4926c7a52de7 ("selftest mm/mseal memory sealing")
> Signed-off-by: longlong yan <yanlonglong@kylinos.cn>

Other than that,

Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

> ---
>  tools/testing/selftests/mm/mseal_test.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/mm/mseal_test.c b/tools/testing/selftests/mm/mseal_test.c
> index faad4833366a..a6ecc81c6aa0 100644
> --- a/tools/testing/selftests/mm/mseal_test.c
> +++ b/tools/testing/selftests/mm/mseal_test.c
> @@ -482,7 +482,7 @@ static void test_seal_zero_address(void)
>  	/* use mmap to change protection. */
>  	ptr = mmap(0, size, PROT_NONE,
>  		   MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0);
> -	FAIL_TEST_IF_FALSE(ptr == 0);
> +	FAIL_TEST_IF_FALSE(ptr == (void *)-1);
>  
>  	size = get_vma_size(ptr, &prot);
>  	FAIL_TEST_IF_FALSE(size == 4 * page_size);
> -- 
> 2.43.0
> 

-- 
Sincerely yours,
Mike.