On Wed, Nov 15, 2023 at 9:34 PM Ilya Leoshkevich <iii@xxxxxxxxxxxxx> wrote: > > Avoid false KMSAN negatives with SLUB_DEBUG by allowing > kmsan_slab_free() to poison the freed memory, and by preventing > init_object() from unpoisoning new allocations. > > Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx> > --- > mm/kmsan/hooks.c | 2 +- > mm/slub.c | 3 ++- > 2 files changed, 3 insertions(+), 2 deletions(-) > > diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c > index 7b5814412e9f..7a30274b893c 100644 > --- a/mm/kmsan/hooks.c > +++ b/mm/kmsan/hooks.c > @@ -76,7 +76,7 @@ void kmsan_slab_free(struct kmem_cache *s, void *object) > return; > > /* RCU slabs could be legally used after free within the RCU period */ > - if (unlikely(s->flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON))) > + if (unlikely(s->flags & SLAB_TYPESAFE_BY_RCU)) > return; > /* > * If there's a constructor, freed memory must remain in the same state > diff --git a/mm/slub.c b/mm/slub.c > index 63d281dfacdb..8d9aa4d7cb7e 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -1024,7 +1024,8 @@ static __printf(3, 4) void slab_err(struct kmem_cache *s, struct slab *slab, > add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); > } > > -static void init_object(struct kmem_cache *s, void *object, u8 val) > +__no_sanitize_memory static void __no_sanitize_memory should be used with great care, because it drops all instrumentation from the function, and any shadow writes will be lost. Won't it be better to add kmsan_poison() to init_object() if you want it to stay uninitialized?
