Messages in this thread | | | From | Alexander Potapenko <> | Date | Fri, 14 May 2021 18:29:18 +0200 | Subject | Re: [PATCH] kasan: slab: always reset the tag in get_freepointer_safe() |
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On Fri, May 14, 2021 at 9:22 AM Alexander Potapenko <glider@google.com> wrote: > > With CONFIG_DEBUG_PAGEALLOC enabled, the kernel should also untag the > object pointer, as done in get_freepointer(). > > Failing to do so reportedly leads to SLUB freelist corruptions that > manifest as boot-time crashes. > > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Marco Elver <elver@google.com> > Cc: Vincenzo Frascino <vincenzo.frascino@arm.com> > Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> > Cc: Andrey Konovalov <andreyknvl@gmail.com> > Cc: Elliot Berman <eberman@codeaurora.org> > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Alexander Potapenko <glider@google.com> > --- > mm/slub.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/slub.c b/mm/slub.c > index feda53ae62ba..9a4f59e5b0c2 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -301,6 +301,7 @@ static inline void *get_freepointer_safe(struct kmem_cache *s, void *object) > if (!debug_pagealloc_enabled_static()) > return get_freepointer(s, object); > > + object = kasan_reset_tag(object); > freepointer_addr = (unsigned long)object + s->offset; > copy_from_kernel_nofault(&p, (void **)freepointer_addr, sizeof(p)); > return freelist_ptr(s, p, freepointer_addr); > -- > 2.31.1.751.gd2f1c929bd-goog >
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