[PATCH 6.7 065/309] selftests/mm: ksm_tests should only MADV_HUGEPAGE valid memory

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6.7-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ryan Roberts <ryan.roberts@xxxxxxx>

commit d021b442cf312664811783e92b3d5e4548e92a53 upstream.

ksm_tests was previously mmapping a region of memory, aligning the
returned pointer to a PMD boundary, then setting MADV_HUGEPAGE, but was
setting it past the end of the mmapped area due to not taking the pointer
alignment into consideration.  Fix this behaviour.

Up until commit efa7df3e3bb5 ("mm: align larger anonymous mappings on THP
boundaries"), this buggy behavior was (usually) masked because the
alignment difference was always less than PMD-size.  But since the
mentioned commit, `ksm_tests -H -s 100` started failing.

Link: https://lkml.kernel.org/r/20240122120554.3108022-1-ryan.roberts@xxxxxxx
Fixes: 325254899684 ("selftests: vm: add KSM huge pages merging time test")
Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: Pedro Demarchi Gomes <pedrodemargomes@xxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 tools/testing/selftests/mm/ksm_tests.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/tools/testing/selftests/mm/ksm_tests.c
+++ b/tools/testing/selftests/mm/ksm_tests.c
@@ -566,7 +566,7 @@ static int ksm_merge_hugepages_time(int
 	if (map_ptr_orig == MAP_FAILED)
 		err(2, "initial mmap");
 
-	if (madvise(map_ptr, len + HPAGE_SIZE, MADV_HUGEPAGE))
+	if (madvise(map_ptr, len, MADV_HUGEPAGE))
 		err(2, "MADV_HUGEPAGE");
 
 	pagemap_fd = open("/proc/self/pagemap", O_RDONLY);






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