From nobody Tue Apr 7 16:28:42 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 455AFECAAA3 for ; Fri, 26 Aug 2022 15:10:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243971AbiHZPKt (ORCPT ); Fri, 26 Aug 2022 11:10:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36648 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245420AbiHZPKB (ORCPT ); Fri, 26 Aug 2022 11:10:01 -0400 Received: from mail-yw1-x1149.google.com (mail-yw1-x1149.google.com [IPv6:2607:f8b0:4864:20::1149]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4EE7BDDAB2 for ; Fri, 26 Aug 2022 08:08:56 -0700 (PDT) Received: by mail-yw1-x1149.google.com with SMTP id 00721157ae682-3363b1dffa0so29064487b3.23 for ; Fri, 26 Aug 2022 08:08:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc; bh=jx2yh37l5SDq2Q8QSIum21pACdE/sm5g4yjUaLUM63Q=; b=YwocNvFxNg+yRyYunyC8K2i0xvtr8YUlMRSXD4KB07qL6OVAVJoi69FVpTqeb6vo98 HNk/rkY+3aMZsuK1uxh+Akq9TcZkV7+UoG9UsOjRo11a/ebkyHu3Zk6ZybTqbnEICNl6 fVKoim3Gbw01E9ari0gpTSeEb1JS1RrQj9AECprq43H/JBol2bhhdu4xkoVyjXPE9+Ze 8ecJmXHBW0h1jwcuB7WCNu3ewzYMljdqqcbJK9oNsyWlgppHytBzzquDRDlGLBrz1LbR 1srEjiZAt2vaWQ/YMD9BNRcRUdlTr4PzP3ErRactmJa3ktJHlpH5z9Y33Q29N2lW/xGz lxzQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc; bh=jx2yh37l5SDq2Q8QSIum21pACdE/sm5g4yjUaLUM63Q=; b=AXVCVSds/aTyyV31L1aWxcr2uIZ27KF1k2xR9CLuuHDyTYFcJakoSAQd309YNDZYSQ YoRZJBgp/cKYXgcVV3/iBNm4ITOpm/Z3BlVnPEa/uJtb+PuMWTtiZKJHXwyyyafitCMn aD7gXbtdMAg8HMojb36/Jgvxs4fJNLmSnEWf5tMbIJWYE8QKzBgRFMkqwv1mG6JgwHJ+ Y+uqc9IN6LRDOW8Gg0kCM2mPuJRBOCSan+zfZVmOB3hBfTg1BHNpqDA+mNxpCOo84xMP Lr6D9zz5XkPsqhn7BBbAK0vxTqLP6wFaSSd86Sc/vjZcpjREjtiC5hsYjVsU4XneuOL8 JiSA== X-Gm-Message-State: ACgBeo0kkbr6a2p30hCxG1eKcJa321a2f4zTXDA4xRMdAZGeHCot1i4O 5/vQYr6C+x3Q4q+6rHABURCf8FU3VTM= X-Google-Smtp-Source: AA6agR603nVbq19tqyU4+Jy5vddr/H1MZ8Z1v7IqPxKbCCNuQvmAeaYyVDn51ytxXs9PxCixOvP5yDsDceQ= X-Received: from glider.muc.corp.google.com ([2a00:79e0:9c:201:5207:ac36:fdd3:502d]) (user=glider job=sendgmr) by 2002:a81:710a:0:b0:33d:c742:4a20 with SMTP id m10-20020a81710a000000b0033dc7424a20mr69884ywc.343.1661526534913; Fri, 26 Aug 2022 08:08:54 -0700 (PDT) Date: Fri, 26 Aug 2022 17:07:38 +0200 In-Reply-To: <20220826150807.723137-1-glider@google.com> Mime-Version: 1.0 References: <20220826150807.723137-1-glider@google.com> X-Mailer: git-send-email 2.37.2.672.g94769d06f0-goog Message-ID: <20220826150807.723137-16-glider@google.com> Subject: [PATCH v5 15/44] mm: kmsan: call KMSAN hooks from SLUB code From: Alexander Potapenko To: glider@google.com Cc: Alexander Viro , Alexei Starovoitov , Andrew Morton , Andrey Konovalov , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Christoph Hellwig , Christoph Lameter , David Rientjes , Dmitry Vyukov , Eric Dumazet , Greg Kroah-Hartman , Herbert Xu , Ilya Leoshkevich , Ingo Molnar , Jens Axboe , Joonsoo Kim , Kees Cook , Marco Elver , Mark Rutland , Matthew Wilcox , "Michael S. Tsirkin" , Pekka Enberg , Peter Zijlstra , Petr Mladek , Steven Rostedt , Thomas Gleixner , Vasily Gorbik , Vegard Nossum , Vlastimil Babka , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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. Signed-off-by: Alexander Potapenko Reviewed-by: Marco Elver --- v2: -- move the implementation of SLUB hooks here v4: -- change sizeof(type) to sizeof(*ptr) -- swap mm: and kmsan: in the subject -- get rid of kmsan_init(), replace it with __no_kmsan_checks v5: -- do not export KMSAN hooks that are not called from modules -- drop an unnecessary whitespace change Link: https://linux-review.googlesource.com/id/I6954b386c5c5d7f99f48bb6cbcc= 74b75136ce86e --- 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 699fe4f5b3bee..fd76cea338878 100644 --- a/include/linux/kmsan.h +++ b/include/linux/kmsan.h @@ -15,6 +15,7 @@ #include =20 struct page; +struct kmem_cache; =20 #ifdef CONFIG_KMSAN =20 @@ -72,6 +73,44 @@ void kmsan_free_page(struct page *page, unsigned int ord= er); */ void kmsan_copy_page_meta(struct page *dst, struct page *src); =20 +/** + * 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 t= he + * 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. @@ -138,6 +177,24 @@ static inline void kmsan_copy_page_meta(struct page *d= st, struct page *src) { } =20 +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 2624b4ea3d8ef..519a7a1dcb4aa 100644 --- a/mm/kmsan/hooks.c +++ b/mm/kmsan/hooks.c @@ -26,6 +26,82 @@ * skipping effects of functions like memset() inside instrumented code. */ =20 +void kmsan_slab_alloc(struct kmem_cache *s, void *object, gfp_t flags) +{ + if (unlikely(object =3D=3D 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 =3D=3D 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 =3D virt_to_head_page((void *)ptr); + KMSAN_WARN_ON(ptr !=3D 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 4ec82bec15ecd..9d0afd2985df7 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -729,6 +729,7 @@ static inline void slab_post_alloc_hook(struct kmem_cac= he *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); } =20 memcg_slab_post_alloc_hook(s, objcg, flags, size, p); diff --git a/mm/slub.c b/mm/slub.c index 862dbd9af4f52..2c323d83d0526 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_cac= he *s, void *object) prefetchw(object + s->offset); } =20 +/* + * When running under KMSAN, get_freepointer_safe() may return an uninitia= lized + * 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 *objec= t) { unsigned long freepointer_addr; @@ -1709,6 +1721,7 @@ static inline void *kmalloc_large_node_hook(void *ptr= , size_t size, gfp_t flags) ptr =3D 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; } =20 @@ -1716,12 +1729,14 @@ static __always_inline void kfree_hook(void *x) { kmemleak_free(x); kasan_kfree_large(x); + kmsan_kfree_large(x); } =20 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); =20 debug_check_no_locks_freed(x, s->object_size); =20 @@ -5915,6 +5930,7 @@ static char *create_unique_id(struct kmem_cache *s) p +=3D sprintf(p, "%07u", s->size); =20 BUG_ON(p > name + ID_STR_LENGTH - 1); + kmsan_unpoison_memory(name, p - name); return name; } =20 @@ -6016,6 +6032,7 @@ static int sysfs_slab_alias(struct kmem_cache *s, con= st char *name) al->name =3D name; al->next =3D alias_list; alias_list =3D al; + kmsan_unpoison_memory(al, sizeof(*al)); return 0; } =20 --=20 2.37.2.672.g94769d06f0-goog