Messages in this thread | | | From | Andrey Konovalov <> | Date | Wed, 13 Feb 2019 14:25:05 +0100 | Subject | Re: [PATCH 4/5] kasan, slub: move kasan_poison_slab hook before page_address |
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On Tue, Feb 12, 2019 at 10:12 PM Andrew Morton <akpm@linux-foundation.org> wrote: > > On Mon, 11 Feb 2019 22:59:53 +0100 Andrey Konovalov <andreyknvl@google.com> wrote: > > > With tag based KASAN page_address() looks at the page flags to see > > whether the resulting pointer needs to have a tag set. Since we don't > > want to set a tag when page_address() is called on SLAB pages, we call > > page_kasan_tag_reset() in kasan_poison_slab(). However in allocate_slab() > > page_address() is called before kasan_poison_slab(). Fix it by changing > > the order. > > > > ... > > > > --- a/mm/slub.c > > +++ b/mm/slub.c > > @@ -1642,12 +1642,15 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node) > > if (page_is_pfmemalloc(page)) > > SetPageSlabPfmemalloc(page); > > > > + kasan_poison_slab(page); > > + > > start = page_address(page); > > > > - if (unlikely(s->flags & SLAB_POISON)) > > + if (unlikely(s->flags & SLAB_POISON)) { > > + metadata_access_enable(); > > memset(start, POISON_INUSE, PAGE_SIZE << order); > > - > > - kasan_poison_slab(page); > > + metadata_access_disable(); > > + } > > > > shuffle = shuffle_freelist(s, page); > > This doesn't compile when CONFIG_SLUB_DEBUG=n. Please review carefully:
Sorry, missed this. I think it makes more sense to move this memset into another function CONFIG_SLUB_DEBUG ifdef, since all other poisoning code is also there. I'll send a v2.
> > --- a/mm/slub.c~kasan-slub-move-kasan_poison_slab-hook-before-page_address-fix > +++ a/mm/slub.c > @@ -1357,6 +1357,14 @@ slab_flags_t kmem_cache_flags(unsigned i > > #define disable_higher_order_debug 0 > > +static inline void metadata_access_enable(void) > +{ > +} > + > +static inline void metadata_access_disable(void) > +{ > +} > + > static inline unsigned long slabs_node(struct kmem_cache *s, int node) > { return 0; } > static inline unsigned long node_nr_slabs(struct kmem_cache_node *n) > _ >
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