From d57a964e09c22441e9fb497d1d7a5c1983a5d1fb Mon Sep 17 00:00:00 2001 From: Andrey Konovalov Date: Thu, 29 Apr 2021 23:00:09 -0700 Subject: [PATCH] kasan, mm: integrate slab init_on_free with HW_TAGS This change uses the previously added memory initialization feature of HW_TAGS KASAN routines for slab memory when init_on_free is enabled. With this change, memory initialization memset() is no longer called when both HW_TAGS KASAN and init_on_free are enabled. Instead, memory is initialized in KASAN runtime. For SLUB, the memory initialization memset() is moved into slab_free_hook() that currently directly follows the initialization loop. A new argument is added to slab_free_hook() that indicates whether to initialize the memory or not. To avoid discrepancies with which memory gets initialized that can be caused by future changes, both KASAN hook and initialization memset() are put together and a warning comment is added. Combining setting allocation tags with memory initialization improves HW_TAGS KASAN performance when init_on_free is enabled. Link: https://lkml.kernel.org/r/190fd15c1886654afdec0d19ebebd5ade665b601.1615296150.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov Reviewed-by: Marco Elver Cc: Alexander Potapenko Cc: Andrey Ryabinin Cc: Branislav Rankov Cc: Catalin Marinas Cc: Christoph Lameter Cc: David Rientjes Cc: Dmitry Vyukov Cc: Evgenii Stepanov Cc: Joonsoo Kim Cc: Kevin Brodsky Cc: Pekka Enberg Cc: Peter Collingbourne Cc: Vincenzo Frascino Cc: Vlastimil Babka Cc: Will Deacon Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/kasan.h | 10 ++++++---- mm/kasan/common.c | 13 +++++++------ mm/slab.c | 15 +++++++++++---- mm/slub.c | 43 ++++++++++++++++++++++++------------------- 4 files changed, 48 insertions(+), 33 deletions(-) diff --git a/include/linux/kasan.h b/include/linux/kasan.h index 629aee484b6c..b1678a61e6a7 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -203,11 +203,13 @@ static __always_inline void * __must_check kasan_init_slab_obj( return (void *)object; } -bool __kasan_slab_free(struct kmem_cache *s, void *object, unsigned long ip); -static __always_inline bool kasan_slab_free(struct kmem_cache *s, void *object) +bool __kasan_slab_free(struct kmem_cache *s, void *object, + unsigned long ip, bool init); +static __always_inline bool kasan_slab_free(struct kmem_cache *s, + void *object, bool init) { if (kasan_enabled()) - return __kasan_slab_free(s, object, _RET_IP_); + return __kasan_slab_free(s, object, _RET_IP_, init); return false; } @@ -313,7 +315,7 @@ static inline void *kasan_init_slab_obj(struct kmem_cache *cache, { return (void *)object; } -static inline bool kasan_slab_free(struct kmem_cache *s, void *object) +static inline bool kasan_slab_free(struct kmem_cache *s, void *object, bool init) { return false; } diff --git a/mm/kasan/common.c b/mm/kasan/common.c index ac0d4ed9c921..6bb87f2acd4e 100644 --- a/mm/kasan/common.c +++ b/mm/kasan/common.c @@ -322,8 +322,8 @@ void * __must_check __kasan_init_slab_obj(struct kmem_cache *cache, return (void *)object; } -static inline bool ____kasan_slab_free(struct kmem_cache *cache, - void *object, unsigned long ip, bool quarantine) +static inline bool ____kasan_slab_free(struct kmem_cache *cache, void *object, + unsigned long ip, bool quarantine, bool init) { u8 tag; void *tagged_object; @@ -351,7 +351,7 @@ static inline bool ____kasan_slab_free(struct kmem_cache *cache, } kasan_poison(object, round_up(cache->object_size, KASAN_GRANULE_SIZE), - KASAN_KMALLOC_FREE, false); + KASAN_KMALLOC_FREE, init); if ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine)) return false; @@ -362,9 +362,10 @@ static inline bool ____kasan_slab_free(struct kmem_cache *cache, return kasan_quarantine_put(cache, object); } -bool __kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip) +bool __kasan_slab_free(struct kmem_cache *cache, void *object, + unsigned long ip, bool init) { - return ____kasan_slab_free(cache, object, ip, true); + return ____kasan_slab_free(cache, object, ip, true, init); } static inline bool ____kasan_kfree_large(void *ptr, unsigned long ip) @@ -409,7 +410,7 @@ void __kasan_slab_free_mempool(void *ptr, unsigned long ip) return; kasan_poison(ptr, page_size(page), KASAN_FREE_PAGE, false); } else { - ____kasan_slab_free(page->slab_cache, ptr, ip, false); + ____kasan_slab_free(page->slab_cache, ptr, ip, false, false); } } diff --git a/mm/slab.c b/mm/slab.c index 84f183e9b31a..df45c437b394 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -3425,17 +3425,24 @@ free_done: static __always_inline void __cache_free(struct kmem_cache *cachep, void *objp, unsigned long caller) { + bool init; + if (is_kfence_address(objp)) { kmemleak_free_recursive(objp, cachep->flags); __kfence_free(objp); return; } - if (unlikely(slab_want_init_on_free(cachep))) + /* + * As memory initialization might be integrated into KASAN, + * kasan_slab_free and initialization memset must be + * kept together to avoid discrepancies in behavior. + */ + init = slab_want_init_on_free(cachep); + if (init && !kasan_has_integrated_init()) memset(objp, 0, cachep->object_size); - - /* Put the object into the quarantine, don't touch it for now. */ - if (kasan_slab_free(cachep, objp)) + /* KASAN might put objp into memory quarantine, delaying its reuse. */ + if (kasan_slab_free(cachep, objp, init)) return; /* Use KCSAN to help debug racy use-after-free. */ diff --git a/mm/slub.c b/mm/slub.c index 5cf35250f20c..68123b21e65f 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1533,7 +1533,8 @@ static __always_inline void kfree_hook(void *x) kasan_kfree_large(x); } -static __always_inline bool slab_free_hook(struct kmem_cache *s, void *x) +static __always_inline bool slab_free_hook(struct kmem_cache *s, + void *x, bool init) { kmemleak_free_recursive(x, s->flags); @@ -1559,8 +1560,25 @@ static __always_inline bool slab_free_hook(struct kmem_cache *s, void *x) __kcsan_check_access(x, s->object_size, KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ASSERT); - /* KASAN might put x into memory quarantine, delaying its reuse */ - return kasan_slab_free(s, x); + /* + * As memory initialization might be integrated into KASAN, + * kasan_slab_free and initialization memset's must be + * kept together to avoid discrepancies in behavior. + * + * The initialization memset's clear the object and the metadata, + * but don't touch the SLAB redzone. + */ + if (init) { + int rsize; + + if (!kasan_has_integrated_init()) + memset(kasan_reset_tag(x), 0, s->object_size); + rsize = (s->flags & SLAB_RED_ZONE) ? s->red_left_pad : 0; + memset((char *)kasan_reset_tag(x) + s->inuse, 0, + s->size - s->inuse - rsize); + } + /* KASAN might put x into memory quarantine, delaying its reuse. */ + return kasan_slab_free(s, x, init); } static inline bool slab_free_freelist_hook(struct kmem_cache *s, @@ -1570,10 +1588,9 @@ static inline bool slab_free_freelist_hook(struct kmem_cache *s, void *object; void *next = *head; void *old_tail = *tail ? *tail : *head; - int rsize; if (is_kfence_address(next)) { - slab_free_hook(s, next); + slab_free_hook(s, next, false); return true; } @@ -1585,20 +1602,8 @@ static inline bool slab_free_freelist_hook(struct kmem_cache *s, object = next; next = get_freepointer(s, object); - if (slab_want_init_on_free(s)) { - /* - * Clear the object and the metadata, but don't touch - * the redzone. - */ - memset(kasan_reset_tag(object), 0, s->object_size); - rsize = (s->flags & SLAB_RED_ZONE) ? s->red_left_pad - : 0; - memset((char *)kasan_reset_tag(object) + s->inuse, 0, - s->size - s->inuse - rsize); - - } /* If object's reuse doesn't have to be delayed */ - if (!slab_free_hook(s, object)) { + if (!slab_free_hook(s, object, slab_want_init_on_free(s))) { /* Move object to the new freelist */ set_freepointer(s, object, *head); *head = object; @@ -3236,7 +3241,7 @@ int build_detached_freelist(struct kmem_cache *s, size_t size, } if (is_kfence_address(object)) { - slab_free_hook(df->s, object); + slab_free_hook(df->s, object, false); __kfence_free(object); p[size] = NULL; /* mark object processed */ return size;