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[66.187.233.206]) by smtp.gmail.com with ESMTPSA id z141sm3056081qka.126.2019.10.18.06.22.24 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 18 Oct 2019 06:22:25 -0700 (PDT) Message-ID: <1571404943.5937.71.camel@lca.pw> Subject: Re: [PATCH RFC v1 18/26] kmsan: mm: call KMSAN hooks from SLUB code From: Qian Cai To: glider@google.com Cc: Andrew Morton , Vegard Nossum , Dmitry Vyukov , linux-mm@kvack.org Date: Fri, 18 Oct 2019 09:22:23 -0400 In-Reply-To: <20191018094304.37056-19-glider@google.com> References: <20191018094304.37056-1-glider@google.com> <20191018094304.37056-19-glider@google.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6 (3.22.6-10.el7) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, 2019-10-18 at 11:42 +0200, glider@google.com wrote: > 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. Well, there is SLUB debug which has red zoning and poisoning checks. What's value of this patch? > > Signed-off-by: Alexander Potapenko > To: Alexander Potapenko > Cc: Andrew Morton > Cc: Vegard Nossum > Cc: Dmitry Vyukov > Cc: linux-mm@kvack.org > --- > > Change-Id: I51103b7981d3aabed747d0c85cbdc85568665871 > --- > mm/slub.c | 37 +++++++++++++++++++++++++++++++------ > 1 file changed, 31 insertions(+), 6 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index 3d63ae320d31..3d6d4c63446e 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -21,6 +21,8 @@ > #include > #include > #include > +#include > +#include /* KMSAN_INIT_VALUE */ > #include > #include > #include > @@ -285,17 +287,27 @@ static void prefetch_freepointer(const struct kmem_cache *s, void *object) > prefetch(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, use KMSAN_INIT_VALUE() to force initialize the > + * return value of get_freepointer_safe(). > + */ > static inline void *get_freepointer_safe(struct kmem_cache *s, void *object) > { > unsigned long freepointer_addr; > void *p; > > if (!debug_pagealloc_enabled()) > - return get_freepointer(s, object); > + return KMSAN_INIT_VALUE(get_freepointer(s, object)); > > freepointer_addr = (unsigned long)object + s->offset; > probe_kernel_read(&p, (void **)freepointer_addr, sizeof(p)); > - return freelist_ptr(s, p, freepointer_addr); > + return KMSAN_INIT_VALUE(freelist_ptr(s, p, freepointer_addr)); > } > > static inline void set_freepointer(struct kmem_cache *s, void *object, void *fp) > @@ -1390,6 +1402,7 @@ 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; > } > > @@ -1397,6 +1410,7 @@ static __always_inline void kfree_hook(void *x) > { > kmemleak_free(x); > kasan_kfree_large(x, _RET_IP_); > + kmsan_kfree_large(x); > } > > static __always_inline bool slab_free_hook(struct kmem_cache *s, void *x) > @@ -1453,6 +1467,12 @@ static inline bool slab_free_freelist_hook(struct kmem_cache *s, > } while (object != old_tail); > } > > + do { > + object = next; > + next = get_freepointer(s, object); > + kmsan_slab_free(s, object); > + } while (object != old_tail); > + > /* > * Compiler cannot detect this function can be removed if slab_free_hook() > * evaluates to nothing. Thus, catch all relevant config debug options here. > @@ -2769,6 +2789,7 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s, > if (unlikely(slab_want_init_on_alloc(gfpflags, s)) && object) > memset(object, 0, s->object_size); > > + kmsan_slab_alloc(s, object, gfpflags); > slab_post_alloc_hook(s, gfpflags, 1, &object); > > return object; > @@ -2797,6 +2818,7 @@ void *kmem_cache_alloc_trace(struct kmem_cache *s, gfp_t gfpflags, size_t size) > void *ret = slab_alloc(s, gfpflags, _RET_IP_); > trace_kmalloc(_RET_IP_, ret, size, s->size, gfpflags); > ret = kasan_kmalloc(s, ret, size, gfpflags); > + > return ret; > } > EXPORT_SYMBOL(kmem_cache_alloc_trace); > @@ -2809,7 +2831,6 @@ void *kmem_cache_alloc_node(struct kmem_cache *s, gfp_t gfpflags, int node) > > trace_kmem_cache_alloc_node(_RET_IP_, ret, > s->object_size, s->size, gfpflags, node); > - > return ret; > } > EXPORT_SYMBOL(kmem_cache_alloc_node); > @@ -2825,6 +2846,7 @@ void *kmem_cache_alloc_node_trace(struct kmem_cache *s, > size, s->size, gfpflags, node); > > ret = kasan_kmalloc(s, ret, size, gfpflags); > + > return ret; > } > EXPORT_SYMBOL(kmem_cache_alloc_node_trace); > @@ -3150,7 +3172,7 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size, > void **p) > { > struct kmem_cache_cpu *c; > - int i; > + int i, j; > > /* memcg and kmem_cache debug support */ > s = slab_pre_alloc_hook(s, flags); > @@ -3188,11 +3210,11 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size, > > /* Clear memory outside IRQ disabled fastpath loop */ > if (unlikely(slab_want_init_on_alloc(flags, s))) { > - int j; > - > for (j = 0; j < i; j++) > memset(p[j], 0, s->object_size); > } > + for (j = 0; j < i; j++) > + kmsan_slab_alloc(s, p[j], flags); > > /* memcg and kmem_cache debug support */ > slab_post_alloc_hook(s, flags, size, p); > @@ -3793,6 +3815,7 @@ static int __init setup_slub_min_objects(char *str) > > __setup("slub_min_objects=", setup_slub_min_objects); > > +__no_sanitize_memory > void *__kmalloc(size_t size, gfp_t flags) > { > struct kmem_cache *s; > @@ -5698,6 +5721,7 @@ 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_shadow(name, p - name); > return name; > } > > @@ -5847,6 +5871,7 @@ static int sysfs_slab_alias(struct kmem_cache *s, const char *name) > al->name = name; > al->next = alias_list; > alias_list = al; > + kmsan_unpoison_shadow(al, sizeof(struct saved_alias)); > return 0; > } >