Commit a8efadda authored by Lorenzo Stoakes's avatar Lorenzo Stoakes Committed by Andrew Morton
Browse files

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

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: 272f37d3 ("tools/selftests: expand all guard region tests to file-backed")
Signed-off-by: default avatarLorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reported-by: default avatarRyan Roberts <ryan.roberts@arm.com>
Closes: https://lore.kernel.org/linux-mm/a2d2766b-0ab4-437b-951a-8595a7506fe9@arm.com/


Reviewed-by: default avatarRyan Roberts <ryan.roberts@arm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent fcaf3b26

tools/testing/selftests/mm/guard-regions.c

+10 −6
Original line number Diff line number Diff line
@@ -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. */