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@xxxxxxxxxx> --- 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 8fa21afcd3fb..a891bc49dc38 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1532,12 +1532,14 @@ 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; } @@ -1614,8 +1616,10 @@ 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 -- 2.18.0.597.ga71716f1ad-goog -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html