Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751791AbdLAVhL (ORCPT ); Fri, 1 Dec 2017 16:37:11 -0500 Received: from mail-io0-f194.google.com ([209.85.223.194]:38516 "EHLO mail-io0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751598AbdLAVhD (ORCPT ); Fri, 1 Dec 2017 16:37:03 -0500 X-Google-Smtp-Source: AGs4zMaL6HO2lnDnPd9oIDnhP3JFcHizV/+t7TKaZoVV49pUSxXIZB3mMONgTFIDs9jNTk3U7MuBug== From: Paul Lawrence To: Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , Masahiro Yamada Cc: linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kbuild@vger.kernel.org, Matthias Kaehlcke , Michael Davidson , Greg Hackmann , Paul Lawrence Subject: [PATCH v3 3/5] kasan: support alloca() poisoning Date: Fri, 1 Dec 2017 13:36:41 -0800 Message-Id: <20171201213643.2506-4-paullawrence@google.com> X-Mailer: git-send-email 2.15.0.531.g2ccb3012c9-goog In-Reply-To: <20171201213643.2506-1-paullawrence@google.com> References: <20171201213643.2506-1-paullawrence@google.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4055 Lines: 118 clang's AddressSanitizer implementation adds redzones on either side of alloca()ed buffers. These redzones are 32-byte aligned and at least 32 bytes long. __asan_alloca_poison() is passed the size and address of the allocated buffer, *excluding* the redzones on either side. The left redzone will always be to the immediate left of this buffer; but AddressSanitizer may need to add padding between the end of the buffer and the right redzone. If there are any 8-byte chunks inside this padding, we should poison those too. __asan_allocas_unpoison() is just passed the top and bottom of the dynamic stack area, so unpoisoning is simpler. Signed-off-by: Greg Hackmann Signed-off-by: Paul Lawrence --- mm/kasan/kasan.c | 34 ++++++++++++++++++++++++++++++++++ mm/kasan/kasan.h | 8 ++++++++ mm/kasan/report.c | 4 ++++ scripts/Makefile.kasan | 3 ++- 4 files changed, 48 insertions(+), 1 deletion(-) diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c index 405bba487df5..d96b36088b2f 100644 --- a/mm/kasan/kasan.c +++ b/mm/kasan/kasan.c @@ -736,6 +736,40 @@ void __asan_unpoison_stack_memory(const void *addr, size_t size) } EXPORT_SYMBOL(__asan_unpoison_stack_memory); +/* Emitted by compiler to poison alloca()ed objects. */ +void __asan_alloca_poison(unsigned long addr, size_t size) +{ + size_t rounded_up_size = round_up(size, KASAN_SHADOW_SCALE_SIZE); + size_t padding_size = round_up(size, KASAN_ALLOCA_REDZONE_SIZE) - + rounded_up_size; + size_t rounded_down_size = round_down(size, KASAN_SHADOW_SCALE_SIZE); + + const void *left_redzone = (const void *)(addr - + KASAN_ALLOCA_REDZONE_SIZE); + const void *right_redzone = (const void *)(addr + rounded_up_size); + + WARN_ON(!IS_ALIGNED(addr, KASAN_ALLOCA_REDZONE_SIZE)); + + kasan_unpoison_shadow((const void *)(addr + rounded_down_size), + size - rounded_down_size); + kasan_poison_shadow(left_redzone, KASAN_ALLOCA_REDZONE_SIZE, + KASAN_ALLOCA_LEFT); + kasan_poison_shadow(right_redzone, + padding_size + KASAN_ALLOCA_REDZONE_SIZE, + KASAN_ALLOCA_RIGHT); +} +EXPORT_SYMBOL(__asan_alloca_poison); + +/* Emitted by compiler to unpoison alloca()ed areas when the stack unwinds. */ +void __asan_allocas_unpoison(const void *stack_top, const void *stack_bottom) +{ + if (unlikely(!stack_top || stack_top > stack_bottom)) + return; + + kasan_unpoison_shadow(stack_top, stack_bottom - stack_top); +} +EXPORT_SYMBOL(__asan_allocas_unpoison); + #ifdef CONFIG_MEMORY_HOTPLUG static int __meminit kasan_mem_notifier(struct notifier_block *nb, unsigned long action, void *data) diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index c70851a9a6a4..7c0bcd1f4c0d 100644 --- a/mm/kasan/kasan.h +++ b/mm/kasan/kasan.h @@ -24,6 +24,14 @@ #define KASAN_STACK_PARTIAL 0xF4 #define KASAN_USE_AFTER_SCOPE 0xF8 +/* + * alloca redzone shadow values + */ +#define KASAN_ALLOCA_LEFT 0xCA +#define KASAN_ALLOCA_RIGHT 0xCB + +#define KASAN_ALLOCA_REDZONE_SIZE 32 + /* Don't break randconfig/all*config builds */ #ifndef KASAN_ABI_VERSION #define KASAN_ABI_VERSION 1 diff --git a/mm/kasan/report.c b/mm/kasan/report.c index 410c8235e671..eff12e040498 100644 --- a/mm/kasan/report.c +++ b/mm/kasan/report.c @@ -102,6 +102,10 @@ static const char *get_shadow_bug_type(struct kasan_access_info *info) case KASAN_USE_AFTER_SCOPE: bug_type = "use-after-scope"; break; + case KASAN_ALLOCA_LEFT: + case KASAN_ALLOCA_RIGHT: + bug_type = "alloca-out-of-bounds"; + break; } return bug_type; diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan index 7c00be9216f4..b4983cf8a9d4 100644 --- a/scripts/Makefile.kasan +++ b/scripts/Makefile.kasan @@ -32,7 +32,8 @@ else $(call cc-param,asan-globals=1) \ $(call cc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \ $(call cc-param,asan-stack=1) \ - $(call cc-param,asan-use-after-scope=1) + $(call cc-param,asan-use-after-scope=1) \ + $(call cc-param,asan-instrument-allocas=1) endif endif -- 2.15.0.531.g2ccb3012c9-goog