From 68ef169a1dd20df5cfa5a161b7304ad9fdd14c36 Mon Sep 17 00:00:00 2001 From: Alexander Potapenko Date: Thu, 15 Sep 2022 17:03:49 +0200 Subject: [PATCH] mm: kmsan: call KMSAN hooks from SLUB code In order to report uninitialized memory coming from heap allocations KMSAN has to poison them unless they're created with __GFP_ZERO. It's handy that we need KMSAN hooks in the places where init_on_alloc/init_on_free initialization is performed. In addition, we apply __no_kmsan_checks to get_freepointer_safe() to suppress reports when accessing freelist pointers that reside in freed objects. Link: https://lkml.kernel.org/r/20220915150417.722975-16-glider@google.com Signed-off-by: Alexander Potapenko Reviewed-by: Marco Elver Cc: Alexander Viro Cc: Alexei Starovoitov Cc: Andrey Konovalov Cc: Andrey Konovalov Cc: Andy Lutomirski Cc: Arnd Bergmann Cc: Borislav Petkov Cc: Christoph Hellwig Cc: Christoph Lameter Cc: David Rientjes Cc: Dmitry Vyukov Cc: Eric Biggers Cc: Eric Biggers Cc: Eric Dumazet Cc: Greg Kroah-Hartman Cc: Herbert Xu Cc: Ilya Leoshkevich Cc: Ingo Molnar Cc: Jens Axboe Cc: Joonsoo Kim Cc: Kees Cook Cc: Mark Rutland Cc: Matthew Wilcox Cc: Michael S. Tsirkin Cc: Pekka Enberg Cc: Peter Zijlstra Cc: Petr Mladek Cc: Stephen Rothwell Cc: Steven Rostedt Cc: Thomas Gleixner Cc: Vasily Gorbik Cc: Vegard Nossum Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- include/linux/kmsan.h | 57 ++++++++++++++++++++++++++++++++ mm/kmsan/hooks.c | 76 +++++++++++++++++++++++++++++++++++++++++++ mm/slab.h | 1 + mm/slub.c | 17 ++++++++++ 4 files changed, 151 insertions(+) diff --git a/include/linux/kmsan.h b/include/linux/kmsan.h index b36bf3db835e..5c4e0079054e 100644 --- a/include/linux/kmsan.h +++ b/include/linux/kmsan.h @@ -14,6 +14,7 @@ #include struct page; +struct kmem_cache; #ifdef CONFIG_KMSAN @@ -48,6 +49,44 @@ void kmsan_free_page(struct page *page, unsigned int order); */ void kmsan_copy_page_meta(struct page *dst, struct page *src); +/** + * kmsan_slab_alloc() - Notify KMSAN about a slab allocation. + * @s: slab cache the object belongs to. + * @object: object pointer. + * @flags: GFP flags passed to the allocator. + * + * Depending on cache flags and GFP flags, KMSAN sets up the metadata of the + * newly created object, marking it as initialized or uninitialized. + */ +void kmsan_slab_alloc(struct kmem_cache *s, void *object, gfp_t flags); + +/** + * kmsan_slab_free() - Notify KMSAN about a slab deallocation. + * @s: slab cache the object belongs to. + * @object: object pointer. + * + * KMSAN marks the freed object as uninitialized. + */ +void kmsan_slab_free(struct kmem_cache *s, void *object); + +/** + * kmsan_kmalloc_large() - Notify KMSAN about a large slab allocation. + * @ptr: object pointer. + * @size: object size. + * @flags: GFP flags passed to the allocator. + * + * Similar to kmsan_slab_alloc(), but for large allocations. + */ +void kmsan_kmalloc_large(const void *ptr, size_t size, gfp_t flags); + +/** + * kmsan_kfree_large() - Notify KMSAN about a large slab deallocation. + * @ptr: object pointer. + * + * Similar to kmsan_slab_free(), but for large allocations. + */ +void kmsan_kfree_large(const void *ptr); + /** * kmsan_map_kernel_range_noflush() - Notify KMSAN about a vmap. * @start: start of vmapped range. @@ -114,6 +153,24 @@ static inline void kmsan_copy_page_meta(struct page *dst, struct page *src) { } +static inline void kmsan_slab_alloc(struct kmem_cache *s, void *object, + gfp_t flags) +{ +} + +static inline void kmsan_slab_free(struct kmem_cache *s, void *object) +{ +} + +static inline void kmsan_kmalloc_large(const void *ptr, size_t size, + gfp_t flags) +{ +} + +static inline void kmsan_kfree_large(const void *ptr) +{ +} + static inline void kmsan_vmap_pages_range_noflush(unsigned long start, unsigned long end, pgprot_t prot, diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c index 040111bb9f6a..000703c563a4 100644 --- a/mm/kmsan/hooks.c +++ b/mm/kmsan/hooks.c @@ -27,6 +27,82 @@ * skipping effects of functions like memset() inside instrumented code. */ +void kmsan_slab_alloc(struct kmem_cache *s, void *object, gfp_t flags) +{ + if (unlikely(object == NULL)) + return; + if (!kmsan_enabled || kmsan_in_runtime()) + return; + /* + * There's a ctor or this is an RCU cache - do nothing. The memory + * status hasn't changed since last use. + */ + if (s->ctor || (s->flags & SLAB_TYPESAFE_BY_RCU)) + return; + + kmsan_enter_runtime(); + if (flags & __GFP_ZERO) + kmsan_internal_unpoison_memory(object, s->object_size, + KMSAN_POISON_CHECK); + else + kmsan_internal_poison_memory(object, s->object_size, flags, + KMSAN_POISON_CHECK); + kmsan_leave_runtime(); +} + +void kmsan_slab_free(struct kmem_cache *s, void *object) +{ + if (!kmsan_enabled || kmsan_in_runtime()) + return; + + /* RCU slabs could be legally used after free within the RCU period */ + if (unlikely(s->flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON))) + return; + /* + * If there's a constructor, freed memory must remain in the same state + * until the next allocation. We cannot save its state to detect + * use-after-free bugs, instead we just keep it unpoisoned. + */ + if (s->ctor) + return; + kmsan_enter_runtime(); + kmsan_internal_poison_memory(object, s->object_size, GFP_KERNEL, + KMSAN_POISON_CHECK | KMSAN_POISON_FREE); + kmsan_leave_runtime(); +} + +void kmsan_kmalloc_large(const void *ptr, size_t size, gfp_t flags) +{ + if (unlikely(ptr == NULL)) + return; + if (!kmsan_enabled || kmsan_in_runtime()) + return; + kmsan_enter_runtime(); + if (flags & __GFP_ZERO) + kmsan_internal_unpoison_memory((void *)ptr, size, + /*checked*/ true); + else + kmsan_internal_poison_memory((void *)ptr, size, flags, + KMSAN_POISON_CHECK); + kmsan_leave_runtime(); +} + +void kmsan_kfree_large(const void *ptr) +{ + struct page *page; + + if (!kmsan_enabled || kmsan_in_runtime()) + return; + kmsan_enter_runtime(); + page = virt_to_head_page((void *)ptr); + KMSAN_WARN_ON(ptr != page_address(page)); + kmsan_internal_poison_memory((void *)ptr, + PAGE_SIZE << compound_order(page), + GFP_KERNEL, + KMSAN_POISON_CHECK | KMSAN_POISON_FREE); + kmsan_leave_runtime(); +} + static unsigned long vmalloc_shadow(unsigned long addr) { return (unsigned long)kmsan_get_metadata((void *)addr, diff --git a/mm/slab.h b/mm/slab.h index 4ec82bec15ec..9d0afd2985df 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -729,6 +729,7 @@ static inline void slab_post_alloc_hook(struct kmem_cache *s, memset(p[i], 0, s->object_size); kmemleak_alloc_recursive(p[i], s->object_size, 1, s->flags, flags); + kmsan_slab_alloc(s, p[i], flags); } memcg_slab_post_alloc_hook(s, objcg, flags, size, p); diff --git a/mm/slub.c b/mm/slub.c index 6953c3367bc2..ce8310e131b3 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -22,6 +22,7 @@ #include #include #include +#include #include #include #include @@ -359,6 +360,17 @@ static void prefetch_freepointer(const struct kmem_cache *s, void *object) prefetchw(object + s->offset); } +/* + * When running under KMSAN, get_freepointer_safe() may return an uninitialized + * pointer value in the case the current thread loses the race for the next + * memory chunk in the freelist. In that case this_cpu_cmpxchg_double() in + * slab_alloc_node() will fail, so the uninitialized value won't be used, but + * KMSAN will still check all arguments of cmpxchg because of imperfect + * handling of inline assembly. + * To work around this problem, we apply __no_kmsan_checks to ensure that + * get_freepointer_safe() returns initialized memory. + */ +__no_kmsan_checks static inline void *get_freepointer_safe(struct kmem_cache *s, void *object) { unsigned long freepointer_addr; @@ -1709,6 +1721,7 @@ static inline void *kmalloc_large_node_hook(void *ptr, size_t size, gfp_t flags) ptr = kasan_kmalloc_large(ptr, size, flags); /* As ptr might get tagged, call kmemleak hook after KASAN. */ kmemleak_alloc(ptr, size, 1, flags); + kmsan_kmalloc_large(ptr, size, flags); return ptr; } @@ -1716,12 +1729,14 @@ static __always_inline void kfree_hook(void *x) { kmemleak_free(x); kasan_kfree_large(x); + kmsan_kfree_large(x); } static __always_inline bool slab_free_hook(struct kmem_cache *s, void *x, bool init) { kmemleak_free_recursive(x, s->flags); + kmsan_slab_free(s, x); debug_check_no_locks_freed(x, s->object_size); @@ -5941,6 +5956,7 @@ static char *create_unique_id(struct kmem_cache *s) p += sprintf(p, "%07u", s->size); BUG_ON(p > name + ID_STR_LENGTH - 1); + kmsan_unpoison_memory(name, p - name); return name; } @@ -6042,6 +6058,7 @@ static int sysfs_slab_alias(struct kmem_cache *s, const char *name) al->name = name; al->next = alias_list; alias_list = al; + kmsan_unpoison_memory(al, sizeof(*al)); return 0; }