[PATCH 5.15 038/402] mm/slub, kunit: Use inverted data to corrupt kmem cache

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

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

From: Guenter Roeck <linux@xxxxxxxxxxxx>

[ Upstream commit b1080c667b3b2c8c38a7fa83ca5567124887abae ]

Two failure patterns are seen randomly when running slub_kunit tests with
CONFIG_SLAB_FREELIST_RANDOM and CONFIG_SLAB_FREELIST_HARDENED enabled.

Pattern 1:
     # test_clobber_zone: pass:1 fail:0 skip:0 total:1
     ok 1 test_clobber_zone
     # test_next_pointer: EXPECTATION FAILED at lib/slub_kunit.c:72
     Expected 3 == slab_errors, but
         slab_errors == 0 (0x0)
     # test_next_pointer: EXPECTATION FAILED at lib/slub_kunit.c:84
     Expected 2 == slab_errors, but
         slab_errors == 0 (0x0)
     # test_next_pointer: pass:0 fail:1 skip:0 total:1
     not ok 2 test_next_pointer

In this case, test_next_pointer() overwrites p[s->offset], but the data
at p[s->offset] is already 0x12.

Pattern 2:
     ok 1 test_clobber_zone
     # test_next_pointer: EXPECTATION FAILED at lib/slub_kunit.c:72
     Expected 3 == slab_errors, but
         slab_errors == 2 (0x2)
     # test_next_pointer: pass:0 fail:1 skip:0 total:1
     not ok 2 test_next_pointer

In this case, p[s->offset] has a value other than 0x12, but one of the
expected failures is nevertheless missing.

Invert data instead of writing a fixed value to corrupt the cache data
structures to fix the problem.

Fixes: 1f9f78b1b376 ("mm/slub, kunit: add a KUnit test for SLUB debugging functionality")
Cc: Oliver Glitta <glittao@xxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
CC: Daniel Latypov <dlatypov@xxxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 lib/slub_kunit.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/slub_kunit.c b/lib/slub_kunit.c
index 8662dc6cb5092..e8b13b62029de 100644
--- a/lib/slub_kunit.c
+++ b/lib/slub_kunit.c
@@ -39,7 +39,7 @@ static void test_next_pointer(struct kunit *test)
 
 	ptr_addr = (unsigned long *)(p + s->offset);
 	tmp = *ptr_addr;
-	p[s->offset] = 0x12;
+	p[s->offset] = ~p[s->offset];
 
 	/*
 	 * Expecting three errors.
-- 
2.43.0







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