From: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Subject: kasan, mm: fix conflicts with init_on_alloc/free A few places where SLUB accesses object's data or metadata were missed in a previous patch. This leads to false positives with hardware tag-based KASAN when bulk allocations are used with init_on_alloc/free. Fix the false-positives by resetting pointer tags during these accesses. (The kasan_reset_tag call is removed from slab_alloc_node, as it's added into maybe_wipe_obj_freeptr.) Link: https://linux-review.googlesource.com/id/I50dd32838a666e173fe06c3c5c766f2c36aae901 Link: https://lkml.kernel.org/r/093428b5d2ca8b507f4a79f92f9929b35f7fada7.1610731872.git.andreyknvl@xxxxxxxxxx Fixes: aa1ef4d7b3f67 ("kasan, mm: reset tags when accessing metadata") Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx> Cc: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx> Cc: Alexander Potapenko <glider@xxxxxxxxxx> Cc: Marco Elver <elver@xxxxxxxxxx> Cc: Will Deacon <will.deacon@xxxxxxx> Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> Cc: Peter Collingbourne <pcc@xxxxxxxxxx> Cc: Evgenii Stepanov <eugenis@xxxxxxxxxx> Cc: Branislav Rankov <Branislav.Rankov@xxxxxxx> Cc: Kevin Brodsky <kevin.brodsky@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/slub.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- a/mm/slub.c~kasan-mm-fix-conflicts-with-init_on_alloc-free +++ a/mm/slub.c @@ -2791,7 +2791,8 @@ static __always_inline void maybe_wipe_o void *obj) { if (unlikely(slab_want_init_on_free(s)) && obj) - memset((void *)((char *)obj + s->offset), 0, sizeof(void *)); + memset((void *)((char *)kasan_reset_tag(obj) + s->offset), + 0, sizeof(void *)); } /* @@ -2883,7 +2884,7 @@ redo: stat(s, ALLOC_FASTPATH); } - maybe_wipe_obj_freeptr(s, kasan_reset_tag(object)); + maybe_wipe_obj_freeptr(s, object); if (unlikely(slab_want_init_on_alloc(gfpflags, s)) && object) memset(kasan_reset_tag(object), 0, s->object_size); @@ -3329,7 +3330,7 @@ int kmem_cache_alloc_bulk(struct kmem_ca int j; for (j = 0; j < i; j++) - memset(p[j], 0, s->object_size); + memset(kasan_reset_tag(p[j]), 0, s->object_size); } /* memcg and kmem_cache debug support */ _
