On Wed, Jan 13, 2021 at 6:25 PM Vlastimil Babka <vbabka@xxxxxxx> wrote: > > 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). The reset has been moved into maybe_wipe_obj_freeptr(). I'll mention it in the changelog in v2. Thanks!
