From patchwork Mon Nov 19 17:26:35 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrey Konovalov X-Patchwork-Id: 10689085 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id BFB4F17FE for ; Mon, 19 Nov 2018 17:28:24 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A41072A2E5 for ; Mon, 19 Nov 2018 17:28:24 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 967F32A2F5; Mon, 19 Nov 2018 17:28:24 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.5 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI, USER_IN_DEF_DKIM_WL autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A22562A2E5 for ; Mon, 19 Nov 2018 17:28:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404860AbeKTDvy (ORCPT ); Mon, 19 Nov 2018 22:51:54 -0500 Received: from mail-wm1-f66.google.com ([209.85.128.66]:53713 "EHLO mail-wm1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404832AbeKTDvy (ORCPT ); Mon, 19 Nov 2018 22:51:54 -0500 Received: by mail-wm1-f66.google.com with SMTP id g131so5752568wmg.3 for ; Mon, 19 Nov 2018 09:27:27 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=90CmP7GgztkoVs5eb+wdJbPAT39DZZS6nz5L6m01xVw=; b=Z829uwYy8LaCaCtdMQBUQg7SxfzQDyhClQnUMCrMDKxxz+OKwYqLeuzWkwQ8ZgCp1j hpf5Vu9xmxJ043Kg4Zypj/n/ep9LAES/ZjMC/nMZendSLLYpZ0Hekt+qydKX8Q2bF6vL NnhmdR7T6LyPusZtKLEaM9i/y8gr2qKcXLi4GkQFwFRelzxa0IDkG1Hn2lAR9XIv/+aA RXcoCZduhW7QoMUppm3nhlHFivZkqRxA6JPhYD1uUgDrmHWwNK6JiMnyNfem/PWMQzjo MCujBSF0Z+ynHFG+e+b0q6pO+hHtVMEbax/tzzvZ0O4hVuK2zNif2BEz4dtBkWAj1hlq 2cNQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=90CmP7GgztkoVs5eb+wdJbPAT39DZZS6nz5L6m01xVw=; b=DyegoTYTITTHxOz/zY5e6/qtxr4OaSCQpQfFyV2iIcQ0x9YrPagPtH/o9cTWvpEyvx 0m6DYq9LT0ZDrZ0lZ/4j2iPXiArpKtY+nCENpOB0o6rfcu4TIWpVjAOwjGwGQouBxd5H KcGIR/XMherMIZ37SqR5dg3AYpTqMyXc9L0mzSuYYogmwjKoQyVbqBXxSa/VaRBtjLcC B0gq40Nd01p8NlM6zyBapwLMzVKmbrIt7nQ4pbZEh9bLPbvUL6NO0At7a6CRR05r1/SS r4EFVS1LGmRSUPt9dmDg3m6pSxHHQxs4XWxfmM3EhWCniKBbauInC5oP5VWV07QZr9OG zQSg== X-Gm-Message-State: AGRZ1gKftOuzv3oalZ44ZxiZ0u0eyzIljH0aPtUYJPEygzB2Hf1ivcFL T7gMlgIRr7cO15iaG3uhUIzuhw== X-Google-Smtp-Source: AJdET5ewESFxx4Uvzbq1mJPzAieXQcvckZ9FZ4+QHYEs9wqzAa/7ORYWdl16jLn9oBffgLx1cCVgUg== X-Received: by 2002:a1c:f514:: with SMTP id t20-v6mr7674084wmh.129.1542648446729; Mon, 19 Nov 2018 09:27:26 -0800 (PST) Received: from andreyknvl0.muc.corp.google.com ([2a00:79e0:15:10:3180:41f8:3010:ff61]) by smtp.gmail.com with ESMTPSA id l143-v6sm23685190wmb.23.2018.11.19.09.27.25 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 19 Nov 2018 09:27:25 -0800 (PST) From: Andrey Konovalov To: Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , Catalin Marinas , Will Deacon , Christoph Lameter , Andrew Morton , Mark Rutland , Nick Desaulniers , Marc Zyngier , Dave Martin , Ard Biesheuvel , "Eric W . Biederman" , Ingo Molnar , Paul Lawrence , Geert Uytterhoeven , Arnd Bergmann , "Kirill A . Shutemov" , Greg Kroah-Hartman , Kate Stewart , Mike Rapoport , kasan-dev@googlegroups.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-sparse@vger.kernel.org, linux-mm@kvack.org, linux-kbuild@vger.kernel.org Cc: Kostya Serebryany , Evgeniy Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Jann Horn , Mark Brand , Chintan Pandya , Vishwath Mohan , Andrey Konovalov Subject: [PATCH v11 19/24] kasan: add hooks implementation for tag-based mode Date: Mon, 19 Nov 2018 18:26:35 +0100 Message-Id: <1ca66e212e466d2d8c2a16c2bbba981d0ab8ec9b.1542648335.git.andreyknvl@google.com> X-Mailer: git-send-email 2.19.1.1215.g8438c0b245-goog In-Reply-To: References: MIME-Version: 1.0 Sender: linux-sparse-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-sparse@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP This commit adds tag-based KASAN specific hooks implementation and adjusts common generic and tag-based KASAN ones. 1. When a new slab cache is created, tag-based KASAN rounds up the size of the objects in this cache to KASAN_SHADOW_SCALE_SIZE (== 16). 2. On each kmalloc tag-based KASAN generates a random tag, sets the shadow memory, that corresponds to this object to this tag, and embeds this tag value into the top byte of the returned pointer. 3. On each kfree tag-based KASAN poisons the shadow memory with a random tag to allow detection of use-after-free bugs. The rest of the logic of the hook implementation is very much similar to the one provided by generic KASAN. Tag-based KASAN saves allocation and free stack metadata to the slab object the same way generic KASAN does. Reviewed-by: Andrey Ryabinin Reviewed-by: Dmitry Vyukov Signed-off-by: Andrey Konovalov --- mm/kasan/common.c | 116 ++++++++++++++++++++++++++++++++++++++-------- mm/kasan/kasan.h | 8 ++++ mm/kasan/tags.c | 48 +++++++++++++++++++ 3 files changed, 153 insertions(+), 19 deletions(-) diff --git a/mm/kasan/common.c b/mm/kasan/common.c index 7134e75447ff..27f0cae336c9 100644 --- a/mm/kasan/common.c +++ b/mm/kasan/common.c @@ -140,6 +140,13 @@ void kasan_poison_shadow(const void *address, size_t size, u8 value) { void *shadow_start, *shadow_end; + /* + * Perform shadow offset calculation based on untagged address, as + * some of the callers (e.g. kasan_poison_object_data) pass tagged + * addresses to this function. + */ + address = reset_tag(address); + shadow_start = kasan_mem_to_shadow(address); shadow_end = kasan_mem_to_shadow(address + size); @@ -148,11 +155,24 @@ void kasan_poison_shadow(const void *address, size_t size, u8 value) void kasan_unpoison_shadow(const void *address, size_t size) { - kasan_poison_shadow(address, size, 0); + u8 tag = get_tag(address); + + /* + * Perform shadow offset calculation based on untagged address, as + * some of the callers (e.g. kasan_unpoison_object_data) pass tagged + * addresses to this function. + */ + address = reset_tag(address); + + kasan_poison_shadow(address, size, tag); if (size & KASAN_SHADOW_MASK) { u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size); - *shadow = size & KASAN_SHADOW_MASK; + + if (IS_ENABLED(CONFIG_KASAN_SW_TAGS)) + *shadow = tag; + else + *shadow = size & KASAN_SHADOW_MASK; } } @@ -200,8 +220,9 @@ void kasan_unpoison_stack_above_sp_to(const void *watermark) void kasan_alloc_pages(struct page *page, unsigned int order) { - if (likely(!PageHighMem(page))) - kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order); + if (unlikely(PageHighMem(page))) + return; + kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order); } void kasan_free_pages(struct page *page, unsigned int order) @@ -218,6 +239,9 @@ void kasan_free_pages(struct page *page, unsigned int order) */ static inline unsigned int optimal_redzone(unsigned int object_size) { + if (IS_ENABLED(CONFIG_KASAN_SW_TAGS)) + return 0; + return object_size <= 64 - 16 ? 16 : object_size <= 128 - 32 ? 32 : @@ -232,6 +256,7 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size, slab_flags_t *flags) { unsigned int orig_size = *size; + unsigned int redzone_size; int redzone_adjust; /* Add alloc meta. */ @@ -239,20 +264,20 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size, *size += sizeof(struct kasan_alloc_meta); /* Add free meta. */ - if (cache->flags & SLAB_TYPESAFE_BY_RCU || cache->ctor || - cache->object_size < sizeof(struct kasan_free_meta)) { + if (IS_ENABLED(CONFIG_KASAN_GENERIC) && + (cache->flags & SLAB_TYPESAFE_BY_RCU || cache->ctor || + cache->object_size < sizeof(struct kasan_free_meta))) { cache->kasan_info.free_meta_offset = *size; *size += sizeof(struct kasan_free_meta); } - redzone_adjust = optimal_redzone(cache->object_size) - - (*size - cache->object_size); + redzone_size = optimal_redzone(cache->object_size); + redzone_adjust = redzone_size - (*size - cache->object_size); if (redzone_adjust > 0) *size += redzone_adjust; *size = min_t(unsigned int, KMALLOC_MAX_SIZE, - max(*size, cache->object_size + - optimal_redzone(cache->object_size))); + max(*size, cache->object_size + redzone_size)); /* * If the metadata doesn't fit, don't enable KASAN at all. @@ -265,6 +290,8 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size, return; } + cache->align = round_up(cache->align, KASAN_SHADOW_SCALE_SIZE); + *flags |= SLAB_KASAN; } @@ -309,6 +336,32 @@ void kasan_poison_object_data(struct kmem_cache *cache, void *object) KASAN_KMALLOC_REDZONE); } +/* + * Since it's desirable to only call object contructors once during slab + * allocation, we preassign tags to all such objects. Also preassign tags for + * SLAB_TYPESAFE_BY_RCU slabs to avoid use-after-free reports. + * For SLAB allocator we can't preassign tags randomly since the freelist is + * stored as an array of indexes instead of a linked list. Assign tags based + * on objects indexes, so that objects that are next to each other get + * different tags. + * After a tag is assigned, the object always gets allocated with the same tag. + * The reason is that we can't change tags for objects with constructors on + * reallocation (even for non-SLAB_TYPESAFE_BY_RCU), because the constructor + * code can save the pointer to the object somewhere (e.g. in the object + * itself). Then if we retag it, the old saved pointer will become invalid. + */ +static u8 assign_tag(struct kmem_cache *cache, const void *object, bool new) +{ + if (!cache->ctor && !(cache->flags & SLAB_TYPESAFE_BY_RCU)) + return new ? KASAN_TAG_KERNEL : random_tag(); + +#ifdef CONFIG_SLAB + return (u8)obj_to_index(cache, virt_to_page(object), (void *)object); +#else + return new ? random_tag() : get_tag(object); +#endif +} + void *kasan_init_slab_obj(struct kmem_cache *cache, const void *object) { struct kasan_alloc_meta *alloc_info; @@ -319,6 +372,9 @@ void *kasan_init_slab_obj(struct kmem_cache *cache, const void *object) alloc_info = get_alloc_info(cache, object); __memset(alloc_info, 0, sizeof(*alloc_info)); + if (IS_ENABLED(CONFIG_KASAN_SW_TAGS)) + object = set_tag(object, assign_tag(cache, object, true)); + return (void *)object; } @@ -327,15 +383,30 @@ void *kasan_slab_alloc(struct kmem_cache *cache, void *object, gfp_t flags) return kasan_kmalloc(cache, object, cache->object_size, flags); } +static inline bool shadow_invalid(u8 tag, s8 shadow_byte) +{ + if (IS_ENABLED(CONFIG_KASAN_GENERIC)) + return shadow_byte < 0 || + shadow_byte >= KASAN_SHADOW_SCALE_SIZE; + else + return tag != (u8)shadow_byte; +} + static bool __kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip, bool quarantine) { s8 shadow_byte; + u8 tag; + void *tagged_object; unsigned long rounded_up_size; + tag = get_tag(object); + tagged_object = object; + object = reset_tag(object); + if (unlikely(nearest_obj(cache, virt_to_head_page(object), object) != object)) { - kasan_report_invalid_free(object, ip); + kasan_report_invalid_free(tagged_object, ip); return true; } @@ -344,20 +415,22 @@ static bool __kasan_slab_free(struct kmem_cache *cache, void *object, return false; shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object)); - if (shadow_byte < 0 || shadow_byte >= KASAN_SHADOW_SCALE_SIZE) { - kasan_report_invalid_free(object, ip); + if (shadow_invalid(tag, shadow_byte)) { + kasan_report_invalid_free(tagged_object, ip); return true; } rounded_up_size = round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE); kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE); - if (!quarantine || unlikely(!(cache->flags & SLAB_KASAN))) + if ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine) || + unlikely(!(cache->flags & SLAB_KASAN))) return false; set_track(&get_alloc_info(cache, object)->free_track, GFP_NOWAIT); quarantine_put(get_free_info(cache, object), cache); - return true; + + return IS_ENABLED(CONFIG_KASAN_GENERIC); } bool kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip) @@ -370,6 +443,7 @@ void *kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size, { unsigned long redzone_start; unsigned long redzone_end; + u8 tag; if (gfpflags_allow_blocking(flags)) quarantine_reduce(); @@ -382,14 +456,18 @@ void *kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size, redzone_end = round_up((unsigned long)object + cache->object_size, KASAN_SHADOW_SCALE_SIZE); - kasan_unpoison_shadow(object, size); + if (IS_ENABLED(CONFIG_KASAN_SW_TAGS)) + tag = assign_tag(cache, object, false); + + /* Tag is ignored in set_tag without CONFIG_KASAN_SW_TAGS */ + kasan_unpoison_shadow(set_tag(object, tag), size); kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start, KASAN_KMALLOC_REDZONE); if (cache->flags & SLAB_KASAN) set_track(&get_alloc_info(cache, object)->alloc_track, flags); - return (void *)object; + return set_tag(object, tag); } EXPORT_SYMBOL(kasan_kmalloc); @@ -439,7 +517,7 @@ void kasan_poison_kfree(void *ptr, unsigned long ip) page = virt_to_head_page(ptr); if (unlikely(!PageSlab(page))) { - if (ptr != page_address(page)) { + if (reset_tag(ptr) != page_address(page)) { kasan_report_invalid_free(ptr, ip); return; } @@ -452,7 +530,7 @@ void kasan_poison_kfree(void *ptr, unsigned long ip) void kasan_kfree_large(void *ptr, unsigned long ip) { - if (ptr != page_address(virt_to_head_page(ptr))) + if (reset_tag(ptr) != page_address(virt_to_head_page(ptr))) kasan_report_invalid_free(ptr, ip); /* The object will be poisoned by page_alloc. */ } diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index 86fc18a21664..5758af10ebe4 100644 --- a/mm/kasan/kasan.h +++ b/mm/kasan/kasan.h @@ -12,10 +12,18 @@ #define KASAN_TAG_INVALID 0xFE /* inaccessible memory tag */ #define KASAN_TAG_MAX 0xFD /* maximum value for random tags */ +#ifdef CONFIG_KASAN_GENERIC #define KASAN_FREE_PAGE 0xFF /* page was freed */ #define KASAN_PAGE_REDZONE 0xFE /* redzone for kmalloc_large allocations */ #define KASAN_KMALLOC_REDZONE 0xFC /* redzone inside slub object */ #define KASAN_KMALLOC_FREE 0xFB /* object was freed (kmem_cache_free/kfree) */ +#else +#define KASAN_FREE_PAGE KASAN_TAG_INVALID +#define KASAN_PAGE_REDZONE KASAN_TAG_INVALID +#define KASAN_KMALLOC_REDZONE KASAN_TAG_INVALID +#define KASAN_KMALLOC_FREE KASAN_TAG_INVALID +#endif + #define KASAN_GLOBAL_REDZONE 0xFA /* redzone for global variable */ /* diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c index 1c4e7ce2e6fe..1d1b79350e28 100644 --- a/mm/kasan/tags.c +++ b/mm/kasan/tags.c @@ -78,15 +78,60 @@ void *kasan_reset_tag(const void *addr) void check_memory_region(unsigned long addr, size_t size, bool write, unsigned long ret_ip) { + u8 tag; + u8 *shadow_first, *shadow_last, *shadow; + void *untagged_addr; + + if (unlikely(size == 0)) + return; + + tag = get_tag((const void *)addr); + + /* + * Ignore accesses for pointers tagged with 0xff (native kernel + * pointer tag) to suppress false positives caused by kmap. + * + * Some kernel code was written to account for archs that don't keep + * high memory mapped all the time, but rather map and unmap particular + * pages when needed. Instead of storing a pointer to the kernel memory, + * this code saves the address of the page structure and offset within + * that page for later use. Those pages are then mapped and unmapped + * with kmap/kunmap when necessary and virt_to_page is used to get the + * virtual address of the page. For arm64 (that keeps the high memory + * mapped all the time), kmap is turned into a page_address call. + + * The issue is that with use of the page_address + virt_to_page + * sequence the top byte value of the original pointer gets lost (gets + * set to KASAN_TAG_KERNEL (0xFF)). + */ + if (tag == KASAN_TAG_KERNEL) + return; + + untagged_addr = reset_tag((const void *)addr); + if (unlikely(untagged_addr < + kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) { + kasan_report(addr, size, write, ret_ip); + return; + } + shadow_first = kasan_mem_to_shadow(untagged_addr); + shadow_last = kasan_mem_to_shadow(untagged_addr + size - 1); + for (shadow = shadow_first; shadow <= shadow_last; shadow++) { + if (*shadow != tag) { + kasan_report(addr, size, write, ret_ip); + return; + } + } } #define DEFINE_HWASAN_LOAD_STORE(size) \ void __hwasan_load##size##_noabort(unsigned long addr) \ { \ + check_memory_region(addr, size, false, _RET_IP_); \ } \ EXPORT_SYMBOL(__hwasan_load##size##_noabort); \ void __hwasan_store##size##_noabort(unsigned long addr) \ { \ + check_memory_region(addr, size, true, _RET_IP_); \ } \ EXPORT_SYMBOL(__hwasan_store##size##_noabort) @@ -98,15 +143,18 @@ DEFINE_HWASAN_LOAD_STORE(16); void __hwasan_loadN_noabort(unsigned long addr, unsigned long size) { + check_memory_region(addr, size, false, _RET_IP_); } EXPORT_SYMBOL(__hwasan_loadN_noabort); void __hwasan_storeN_noabort(unsigned long addr, unsigned long size) { + check_memory_region(addr, size, true, _RET_IP_); } EXPORT_SYMBOL(__hwasan_storeN_noabort); void __hwasan_tag_memory(unsigned long addr, u8 tag, unsigned long size) { + kasan_poison_shadow((void *)addr, size, tag); } EXPORT_SYMBOL(__hwasan_tag_memory);