git/linux-cryptodev-2.6
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/herbert/cryptodev-2.6.git synced 2026-04-28 21:46:02 -04:00
Code Issues Packages Projects Releases Wiki Activity

selftests/mm: fix UFFDIO_API usage with proper two-step feature negotiation

Browse Source 
The current implementation of test_unmerge_uffd_wp() explicitly sets
`uffdio_api.features = UFFD_FEATURE_PAGEFAULT_FLAG_WP` before calling
UFFDIO_API.  This can cause the ioctl() call to fail with EINVAL on
kernels that do not support UFFD-WP, leading the test to fail
unnecessarily:

  # ------------------------------
  # running ./ksm_functional_tests
  # ------------------------------
  # TAP version 13
  # 1..9
  # # [RUN] test_unmerge
  # ok 1 Pages were unmerged
  # # [RUN] test_unmerge_zero_pages
  # ok 2 KSM zero pages were unmerged
  # # [RUN] test_unmerge_discarded
  # ok 3 Pages were unmerged
  # # [RUN] test_unmerge_uffd_wp
  # not ok 4 UFFDIO_API failed     <-----
  # # [RUN] test_prot_none
  # ok 5 Pages were unmerged
  # # [RUN] test_prctl
  # ok 6 Setting/clearing PR_SET_MEMORY_MERGE works
  # # [RUN] test_prctl_fork
  # # No pages got merged
  # # [RUN] test_prctl_fork_exec
  # ok 7 PR_SET_MEMORY_MERGE value is inherited
  # # [RUN] test_prctl_unmerge
  # ok 8 Pages were unmerged
  # Bail out! 1 out of 8 tests failed
  # # Planned tests != run tests (9 != 8)
  # # Totals: pass:7 fail:1 xfail:0 xpass:0 skip:0 error:0
  # [FAIL]

This patch improves compatibility and robustness of the UFFD-WP test
(test_unmerge_uffd_wp) by correctly implementing the UFFDIO_API two-step
handshake as recommended by the userfaultfd(2) man page.

Key changes:

1. Use features=0 in the initial UFFDIO_API call to query supported
   feature bits, rather than immediately requesting WP support.

2. Skip the test gracefully if:
   - UFFDIO_API fails with EINVAL (e.g. unsupported API version), or
   - UFFD_FEATURE_PAGEFAULT_FLAG_WP is not advertised by the kernel.

3. Close the initial userfaultfd and create a new one before enabling
   the required feature, since UFFDIO_API can only be called once per fd.

4. Improve diagnostics by distinguishing between expected and unexpected
   failures, using strerror() to report errors.

This ensures the test behaves correctly across a wider range of kernel
versions and configurations, while preserving the intended behavior on
kernels that support UFFD-WP.

[liwang@redhat.com: fail the test if sys_userfaultfd() fails, per David]
  Link: https://lkml.kernel.org/r/20250625004645.400520-1-liwang@redhat.com
Link: https://lkml.kernel.org/r/20250624042411.395285-1-liwang@redhat.com
Signed-off-by: Li Wang <liwang@redhat.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Aruna Ramakrishna <aruna.ramakrishna@oracle.com>
Cc: Bagas Sanjaya <bagasdotme@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Keith Lucas <keith.lucas@oracle.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Li Wang <liwang@redhat.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Li Wang
2025-06-24 12:24:11 +08:00
committed by Andrew Morton
parent 1f0bce2fa8
commit 98db4b5472
1 changed files with 26 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

28
tools/testing/selftests/mm/ksm_functional_tests.c
View File

@@ -393,9 +393,13 @@ static void test_unmerge_uffd_wp(void)
/* See if UFFD-WP is around. */
uffdio_api.api = UFFD_API;
uffdio_api.features = UFFD_FEATURE_PAGEFAULT_FLAG_WP;
uffdio_api.features = 0;
if (ioctl(uffd, UFFDIO_API, &uffdio_api) < 0) {
ksft_test_result_fail("UFFDIO_API failed\n");
if (errno == EINVAL)
ksft_test_result_skip("The API version requested is not supported\n");
else
ksft_test_result_fail("UFFDIO_API failed: %s\n", strerror(errno));
goto close_uffd;
}
if (!(uffdio_api.features & UFFD_FEATURE_PAGEFAULT_FLAG_WP)) {
@@ -403,6 +407,26 @@ static void test_unmerge_uffd_wp(void)
goto close_uffd;
}
/*
* UFFDIO_API must only be called once to enable features.
* So we close the old userfaultfd and create a new one to
* actually enable UFFD_FEATURE_PAGEFAULT_FLAG_WP.
*/
close(uffd);
uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
if (uffd < 0) {
ksft_test_result_fail("__NR_userfaultfd failed\n");
goto unmap;
}
/* Now, enable it ("two-step handshake") */
uffdio_api.api = UFFD_API;
uffdio_api.features = UFFD_FEATURE_PAGEFAULT_FLAG_WP;
if (ioctl(uffd, UFFDIO_API, &uffdio_api) < 0) {
ksft_test_result_fail("UFFDIO_API failed: %s\n", strerror(errno));
goto close_uffd;
}
/* Register UFFD-WP, no need for an actual handler. */
if (uffd_register(uffd, map, size, false, true, false)) {
ksft_test_result_fail("UFFDIO_REGISTER_MODE_WP failed\n");