On 1/13/21 5:03 PM, Andrey Konovalov wrote: > 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. > > Link: https://linux-review.googlesource.com/id/I50dd32838a666e173fe06c3c5c766f2c36aae901 > Fixes: aa1ef4d7b3f67 ("kasan, mm: reset tags when accessing metadata") > Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx> > --- > mm/slub.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index dc5b42e700b8..75fb097d990d 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -2791,7 +2791,8 @@ static __always_inline void maybe_wipe_obj_freeptr(struct kmem_cache *s, > 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 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s, > stat(s, ALLOC_FASTPATH); > } > > - maybe_wipe_obj_freeptr(s, kasan_reset_tag(object)); > + maybe_wipe_obj_freeptr(s, object); And in that case the reset was unnecessary, right. (commit log only mentions adding missing resets). > 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_cache *s, gfp_t flags, size_t size, > 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 */ >
