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mm/slub, kunit: Use inverted data to corrupt kmem cache

Nico Pache requested to merge npache/centos-stream-9:slubtestfix into main 
mm/slub, kunit: Use inverted data to corrupt kmem cache
    
    commit b1080c667b3b2c8c38a7fa83ca5567124887abae
    Author: Guenter Roeck <linux@roeck-us.net>
    Date:   Tue Apr 2 06:38:39 2024 -0700
    
        mm/slub, kunit: Use inverted data to corrupt kmem cache
    
        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")

JIRA: https://issues.redhat.com/browse/RHEL-38018

Signed-off-by: Nico Pache npache@redhat.com

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