Re: [PATCH v4 13/14] selftests/mm: add userfaultfd RWP tests

Re: [PATCH v4 13/14] selftests/mm: add userfaultfd RWP tests

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Hardcoding _UFFDIO_SET_MODE in the unconditionally checked expected_ioctls breaks the userfaultfd selftests on older kernels.
--

commit 2e7d7c5845ff822166d0f5b0dd880bef4b890a15
Author: Kiryl Shutsemau (Meta) <kas@kernel.org>
selftests/mm: add userfaultfd RWP tests

This commit adds coverage for UFFDIO_REGISTER_MODE_RWP and UFFDIO_RWPROTECT.
It introduces multiple test cases for sync and async modes, mprotect
interactions, GUP paths, and fork behaviors.

> diff --git a/tools/testing/selftests/mm/uffd-unit-tests.c b/tools/testing/selftests/mm/uffd-unit-tests.c
> index a6c14109e8188..bd6f35ddaa4d0 100644
> --- a/tools/testing/selftests/mm/uffd-unit-tests.c
> +++ b/tools/testing/selftests/mm/uffd-unit-tests.c
> @@ -109,6 +111,11 @@ static void uffd_test_skip(const char *message)
>  
>  static void test_uffd_api(bool use_dev)
>  {
> +	const uint64_t expected_ioctls =
> +		BIT_ULL(_UFFDIO_REGISTER) |
> +		BIT_ULL(_UFFDIO_UNREGISTER) |
> +		BIT_ULL(_UFFDIO_API) |
> +		BIT_ULL(_UFFDIO_SET_MODE);
>  	struct uffdio_api uffdio_api;
>  	int uffd;

[ ... ]

> @@ -148,6 +155,15 @@ static void test_uffd_api(bool use_dev)
>  		goto out;
>  	}
>  
> +	/* Verify returned fd-level ioctls bitmask */
> +	if ((uffdio_api.ioctls & expected_ioctls) != expected_ioctls) {
> +		uffd_test_fail("UFFDIO_API missing expected ioctls: "

[Severity: Medium]
Will this unconditional check cause the baseline test_uffd_api to fail on
older kernels that do not support UFFDIO_SET_MODE? Since the selftests are
usually expected to gracefully skip unsupported tests, it seems hardcoding
this bit into expected_ioctls might break backward compatibility for the
test suite.

> +			       "got=0x%"PRIx64", expected=0x%"PRIx64,
> +			       (uint64_t)uffdio_api.ioctls,
> +			       expected_ioctls);
> +		goto out;
> +	}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260525113737.1942478-1-kas@kernel.org?part=13

Re: [PATCH v4 13/14] selftests/mm: add userfaultfd RWP tests

[Kiryl Shutsemau]

On Mon, May 25, 2026 at 12:39:03PM +0000, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [Medium] Hardcoding _UFFDIO_SET_MODE in the unconditionally checked
> expected_ioctls breaks the userfaultfd selftests on older kernels.

Will be fixed in v5 -- dropped _UFFDIO_SET_MODE from expected_ioctls in
test_uffd_api(). The dedicated RWP tests already exercise the ioctl
directly and err if it's not supported, so SET_MODE coverage isn't lost.

> -- 
> Sashiko AI review · https://sashiko.dev/#/patchset/20260525113737.1942478-1-kas@kernel.org?part=13

-- 
  Kiryl Shutsemau / Kirill A. Shutemov