From 4d176711ea7a8d4873e7157ac6ab242ade3ba351 Mon Sep 17 00:00:00 2001 From: Andrey Konovalov Date: Fri, 28 Dec 2018 00:30:23 -0800 Subject: kasan: preassign tags to objects with ctors or SLAB_TYPESAFE_BY_RCU 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. Link: http://lkml.kernel.org/r/f158a8a74a031d66f0a9398a5b0ed453c37ba09a.1544099024.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov Reviewed-by: Andrey Ryabinin Reviewed-by: Dmitry Vyukov Cc: Christoph Lameter Cc: Mark Rutland Cc: Will Deacon Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/slub.c | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-) (limited to 'mm/slub.c') diff --git a/mm/slub.c b/mm/slub.c index e739d46600b9..08740c3f3745 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1451,16 +1451,17 @@ static inline bool slab_free_freelist_hook(struct kmem_cache *s, #endif } -static void setup_object(struct kmem_cache *s, struct page *page, +static void *setup_object(struct kmem_cache *s, struct page *page, void *object) { setup_object_debug(s, page, object); - kasan_init_slab_obj(s, object); + object = kasan_init_slab_obj(s, object); if (unlikely(s->ctor)) { kasan_unpoison_object_data(s, object); s->ctor(object); kasan_poison_object_data(s, object); } + return object; } /* @@ -1568,16 +1569,16 @@ 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 = setup_object(s, page, 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 = setup_object(s, page, next); set_freepointer(s, cur, next); cur = next; } - setup_object(s, page, cur); set_freepointer(s, cur, NULL); return true; @@ -1599,7 +1600,7 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node) struct page *page; struct kmem_cache_order_objects oo = s->oo; gfp_t alloc_gfp; - void *start, *p; + void *start, *p, *next; int idx, order; bool shuffle; @@ -1651,13 +1652,16 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node) if (!shuffle) { for_each_object_idx(p, idx, s, start, page->objects) { - setup_object(s, page, p); - if (likely(idx < page->objects)) - set_freepointer(s, p, p + s->size); - else + if (likely(idx < page->objects)) { + next = p + s->size; + next = setup_object(s, page, next); + set_freepointer(s, p, next); + } else set_freepointer(s, p, NULL); } - page->freelist = fixup_red_left(s, start); + start = fixup_red_left(s, start); + start = setup_object(s, page, start); + page->freelist = start; } page->inuse = page->objects; -- cgit v1.2.3