| Message ID | 95b5beb7ec13b7e998efe84c9a7a5c1fa49a9fe3.1535462971.git.andreyknvl@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | khwasan: kernel hardware assisted address sanitizer | expand |
On Wed, Aug 29, 2018 at 1:35 PM, Andrey Konovalov <andreyknvl@google.com> wrote: > An object constructor can initialize pointers within this objects based on > the address of the object. Since the object address might be tagged, we > need to assign a tag before calling constructor. > > The implemented approach is to assign tags to objects with constructors > when a slab is allocated and call constructors once as usual. The > downside is that such object would always have the same tag when it is > reallocated, so we won't catch use-after-frees on it. > > Also pressign tags for objects from SLAB_TYPESAFE_BY_RCU caches, since > they can be validy accessed after having been freed. > > Signed-off-by: Andrey Konovalov <andreyknvl@google.com> > --- > mm/slab.c | 6 +++++- > mm/slub.c | 4 ++++ > 2 files changed, 9 insertions(+), 1 deletion(-) > > diff --git a/mm/slab.c b/mm/slab.c > index 6fdca9ec2ea4..3b4227059f2e 100644 > --- a/mm/slab.c > +++ b/mm/slab.c > @@ -403,7 +403,11 @@ static inline struct kmem_cache *virt_to_cache(const void *obj) > static inline void *index_to_obj(struct kmem_cache *cache, struct page *page, > unsigned int idx) > { > - return page->s_mem + cache->size * idx; > + void *obj; > + > + obj = page->s_mem + cache->size * idx; > + obj = khwasan_preset_slab_tag(cache, idx, obj); > + return obj; > } > > /* > diff --git a/mm/slub.c b/mm/slub.c > index 4206e1b616e7..086d6558a6b6 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -1531,12 +1531,14 @@ static bool shuffle_freelist(struct kmem_cache *s, struct page *page) > /* First entry is used as the base of the freelist */ > cur = next_freelist_entry(s, page, &pos, start, page_limit, > freelist_count); > + cur = khwasan_preset_slub_tag(s, cur); > page->freelist = cur; > > for (idx = 1; idx < page->objects; idx++) { > setup_object(s, page, cur); > next = next_freelist_entry(s, page, &pos, start, page_limit, > freelist_count); > + next = khwasan_preset_slub_tag(s, next); > set_freepointer(s, cur, next); > cur = next; > } > @@ -1613,8 +1615,10 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node) > shuffle = shuffle_freelist(s, page); > > if (!shuffle) { > + start = khwasan_preset_slub_tag(s, start); > for_each_object_idx(p, idx, s, start, page->objects) { > setup_object(s, page, p); > + p = khwasan_preset_slub_tag(s, p); As I commented in the previous patch, can't we do this in kasan_init_slab_obj(), which should be called in all the right places already? > if (likely(idx < page->objects)) > set_freepointer(s, p, p + s->size); > else > -- > 2.19.0.rc0.228.g281dcd1b4d0-goog >
On Wed, Sep 12, 2018 at 6:36 PM, Dmitry Vyukov <dvyukov@google.com> wrote: > On Wed, Aug 29, 2018 at 1:35 PM, Andrey Konovalov <andreyknvl@google.com> wrote: >> if (!shuffle) { >> + start = khwasan_preset_slub_tag(s, start); >> for_each_object_idx(p, idx, s, start, page->objects) { >> setup_object(s, page, p); >> + p = khwasan_preset_slub_tag(s, p); > > > As I commented in the previous patch, can't we do this in > kasan_init_slab_obj(), which should be called in all the right places > already? > As per offline discussion, will do in v7.
diff --git a/mm/slab.c b/mm/slab.c index 6fdca9ec2ea4..3b4227059f2e 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -403,7 +403,11 @@ static inline struct kmem_cache *virt_to_cache(const void *obj) static inline void *index_to_obj(struct kmem_cache *cache, struct page *page, unsigned int idx) { - return page->s_mem + cache->size * idx; + void *obj; + + obj = page->s_mem + cache->size * idx; + obj = khwasan_preset_slab_tag(cache, idx, obj); + return obj; } /* diff --git a/mm/slub.c b/mm/slub.c index 4206e1b616e7..086d6558a6b6 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1531,12 +1531,14 @@ static bool shuffle_freelist(struct kmem_cache *s, struct page *page) /* First entry is used as the base of the freelist */ cur = next_freelist_entry(s, page, &pos, start, page_limit, freelist_count); + cur = khwasan_preset_slub_tag(s, cur); page->freelist = cur; for (idx = 1; idx < page->objects; idx++) { setup_object(s, page, cur); next = next_freelist_entry(s, page, &pos, start, page_limit, freelist_count); + next = khwasan_preset_slub_tag(s, next); set_freepointer(s, cur, next); cur = next; } @@ -1613,8 +1615,10 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node) shuffle = shuffle_freelist(s, page); if (!shuffle) { + start = khwasan_preset_slub_tag(s, start); for_each_object_idx(p, idx, s, start, page->objects) { setup_object(s, page, p); + p = khwasan_preset_slub_tag(s, p); if (likely(idx < page->objects)) set_freepointer(s, p, p + s->size); else
An object constructor can initialize pointers within this objects based on the address of the object. Since the object address might be tagged, we need to assign a tag before calling constructor. The implemented approach is to assign tags to objects with constructors when a slab is allocated and call constructors once as usual. The downside is that such object would always have the same tag when it is reallocated, so we won't catch use-after-frees on it. Also pressign tags for objects from SLAB_TYPESAFE_BY_RCU caches, since they can be validy accessed after having been freed. Signed-off-by: Andrey Konovalov <andreyknvl@google.com> --- mm/slab.c | 6 +++++- mm/slub.c | 4 ++++ 2 files changed, 9 insertions(+), 1 deletion(-)