The patch titled Subject: tools/testing/selftests: fix guard region test tmpfs assumption has been added to the -mm mm-hotfixes-unstable branch. Its filename is tools-testing-selftests-fix-guard-region-test-tmpfs-assumption.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Lorenzo Stoakes lorenzo.stoakes@oracle.com Subject: tools/testing/selftests: fix guard region test tmpfs assumption Date: Fri, 25 Apr 2025 17:24:36 +0100

The current implementation of the guard region tests assume that /tmp is mounted as tmpfs, that is shmem.

This isn't always the case, and at least one instance of a spurious test failure has been reported as a result.

This assumption is unsafe, rushed and silly - and easily remedied by simply using memfd, so do so.

We also have to fixup the readonly_file test to explicitly only be applicable to file-backed cases.

Link: https://lkml.kernel.org/r/20250425162436.564002-1-lorenzo.stoakes@oracle.com Fixes: 272f37d3e99a ("tools/selftests: expand all guard region tests to file-backed") Signed-off-by: Lorenzo Stoakes lorenzo.stoakes@oracle.com Reported-by: Ryan Roberts ryan.roberts@arm.com Closes: https://lore.kernel.org/linux-mm/a2d2766b-0ab4-437b-951a-8595a7506fe9@arm.co... Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

tools/testing/selftests/mm/guard-regions.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-)

--- a/tools/testing/selftests/mm/guard-regions.c~tools-testing-selftests-fix-guard-region-test-tmpfs-assumption +++ a/tools/testing/selftests/mm/guard-regions.c @@ -271,12 +271,16 @@ FIXTURE_SETUP(guard_regions) self->page_size = (unsigned long)sysconf(_SC_PAGESIZE); setup_sighandler();

- if (variant->backing == ANON_BACKED) + switch (variant->backing) { + case ANON_BACKED: return; - - self->fd = open_file( - variant->backing == SHMEM_BACKED ? "/tmp/" : "", - self->path); + case LOCAL_FILE_BACKED: + self->fd = open_file("", self->path); + break; + case SHMEM_BACKED: + self->fd = memfd_create(self->path, 0); + break; + }

/* We truncate file to at least 100 pages, tests can modify as needed. */ ASSERT_EQ(ftruncate(self->fd, 100 * self->page_size), 0); @@ -1696,7 +1700,7 @@ TEST_F(guard_regions, readonly_file) char *ptr; int i;

- if (variant->backing == ANON_BACKED) + if (variant->backing != LOCAL_FILE_BACKED) SKIP(return, "Read-only test specific to file-backed");

/* Map shared so we can populate with pattern, populate it, unmap. */ _

Patches currently in -mm which might be from lorenzo.stoakes@oracle.com are

maintainers-add-reverse-mapping-section.patch maintainers-add-core-mm-section.patch maintainers-add-mm-thp-section.patch maintainers-add-mm-thp-section-fix.patch tools-testing-selftests-fix-guard-region-test-tmpfs-assumption.patch mm-vma-fix-incorrectly-disallowed-anonymous-vma-merges.patch tools-testing-add-procmap_query-helper-functions-in-mm-self-tests.patch tools-testing-selftests-assert-that-anon-merge-cases-behave-as-expected.patch mm-move-mmap-vma-locking-logic-into-specific-files.patch