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tools/testing/selftests: fix guard region test tmpfs assumption

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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: 272f37d3e9 ("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.com/
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Lorenzo Stoakes
2025-04-25 17:24:36 +01:00
committed by Andrew Morton
parent fcaf3b2683
commit a8efadda86
1 changed files with 10 additions and 6 deletions
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tools/testing/selftests/mm/guard-regions.c
+10 -6
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@@ -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. */