From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, T_DKIMWL_WL_MED,USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D3606C43144 for ; Tue, 26 Jun 2018 13:19:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8381E26805 for ; Tue, 26 Jun 2018 13:19:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="aUpOkcHC" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8381E26805 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935519AbeFZNPw (ORCPT ); Tue, 26 Jun 2018 09:15:52 -0400 Received: from mail-wr0-f196.google.com ([209.85.128.196]:44868 "EHLO mail-wr0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935475AbeFZNPr (ORCPT ); Tue, 26 Jun 2018 09:15:47 -0400 Received: by mail-wr0-f196.google.com with SMTP id p12-v6so15588895wrn.11 for ; Tue, 26 Jun 2018 06:15:46 -0700 (PDT) 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=fesVdV6LHBRKNYXBdcmV3hEtSKqlEwR3jkeYNaPRqlo=; b=aUpOkcHC77zwPdvoyCQWtOFI+/au+FXWE52sbYSgk55WFZZJey0GTTHuKlizoKzXeQ aP/dBwRPsy4C/094DdAhIqj0xjNqS00ncYdzLTD9q89aCxs8ifz1U+R7zJRpZJ6QVZuL yBci2MkmwKvNOE4VQKRiG4K98ib3Qb/piWGQzB6OWyTn0fHUl9X+n2tG5HSF4lbmnslB eg/meZ77q//+1bQ22jFd1ecR4XRGxFm5X06IXQdRm2ZlPtUlSLdtHN5mdFibsO2zCGdt pPFG8p1lKJtytCwX6u7AeC7WNInj90vgSHzo8M/97SGtY+9HUDEUE78z7oUmxv88cirE Jl0w== 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=fesVdV6LHBRKNYXBdcmV3hEtSKqlEwR3jkeYNaPRqlo=; b=GOUPz+9JQlcCt4VfuU4XVcosPi8fDkIJCq9gYFHnMTgyZnE791ULlhJcbpp6fMmaBr 94C875O+k3cGWFN3Hkttqye5wlBztvzwG9I/YMLTbGsWu4TNf8S7MpIyfky4j72xDPXC /vShZuBiB1bQKuFW8GlpYxdbsCqUMvuKSOIY36OqrHd0XwZ1eqBPY16S8upFsvHOT+d6 93ZD4PuNqoEGBiUUvwJ03gcBB/9rcmh32r0O4MuEuqupsBDvuRJBD1fl2qqO6iKSnQ2q XirWGAG1wHbUzG95UA++8ZtZN6V6gsO36oAMpbn6ddgk97iTKb0z0lcyF69KlFxXBVzz wyLg== X-Gm-Message-State: APt69E2pUiLbX2rkUdVbvhW3dSnkPEmI0K2QyFKbrgRGDie54tx+vzIX /ldGS5GTXStcthDmxJoBu5XZdQ== X-Google-Smtp-Source: AAOMgpftwzrXVmZLeNoHXgsYfWg8uDR2FTtM+E+3Y3BKpb9eMVhCZovEfRNDcfa5ONzdpycmM2ScgQ== X-Received: by 2002:adf:9063:: with SMTP id h90-v6mr1519403wrh.147.1530018945895; Tue, 26 Jun 2018 06:15:45 -0700 (PDT) Received: from andreyknvl0.muc.corp.google.com ([2a00:79e0:15:10:84be:a42a:826d:c530]) by smtp.gmail.com with ESMTPSA id w15-v6sm2162639wrn.25.2018.06.26.06.15.43 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 26 Jun 2018 06:15:44 -0700 (PDT) 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 , Andrey Konovalov Subject: [PATCH v4 07/17] khwasan: add tag related helper functions Date: Tue, 26 Jun 2018 15:15:17 +0200 Message-Id: <0aaff2112647cc4b3aaa1a2be127285dcb5af2c5.1530018818.git.andreyknvl@google.com> X-Mailer: git-send-email 2.18.0.rc2.346.g013aa6912e-goog In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This commit adds a few helper functions, that are meant to be used to work with tags embedded in the top byte of kernel pointers: to set, to get or to reset (set to 0xff) the top byte. Signed-off-by: Andrey Konovalov --- arch/arm64/mm/kasan_init.c | 2 ++ include/linux/kasan.h | 23 ++++++++++++++++ mm/kasan/kasan.h | 55 ++++++++++++++++++++++++++++++++++++++ mm/kasan/khwasan.c | 47 ++++++++++++++++++++++++++++++++ 4 files changed, 127 insertions(+) diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c index 7a31e8ccbad2..e7f37c0b7e14 100644 --- a/arch/arm64/mm/kasan_init.c +++ b/arch/arm64/mm/kasan_init.c @@ -250,6 +250,8 @@ void __init kasan_init(void) memset(kasan_zero_page, KASAN_SHADOW_INIT, PAGE_SIZE); cpu_replace_ttbr1(lm_alias(swapper_pg_dir)); + khwasan_init(); + /* At this point kasan is fully initialized. Enable error messages */ init_task.kasan_depth = 0; pr_info("KernelAddressSanitizer initialized\n"); diff --git a/include/linux/kasan.h b/include/linux/kasan.h index 336385baf926..d7624b879d86 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -155,6 +155,29 @@ static inline void kasan_cache_shutdown(struct kmem_cache *cache) {} #define KASAN_SHADOW_INIT 0xFF +void khwasan_init(void); + +void *khwasan_set_tag(const void *addr, u8 tag); +u8 khwasan_get_tag(const void *addr); +void *khwasan_reset_tag(const void *ptr); + +#else /* CONFIG_KASAN_HW */ + +static inline void khwasan_init(void) { } + +static inline void *khwasan_set_tag(const void *addr, u8 tag) +{ + return (void *)addr; +} +static inline u8 khwasan_get_tag(const void *addr) +{ + return 0xFF; +} +static inline void *khwasan_reset_tag(const void *ptr) +{ + return (void *)ptr; +} + #endif /* CONFIG_KASAN_HW */ #endif /* LINUX_KASAN_H */ diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index 19b950eaccff..a7cc27d96608 100644 --- a/mm/kasan/kasan.h +++ b/mm/kasan/kasan.h @@ -8,6 +8,10 @@ #define KASAN_SHADOW_SCALE_SIZE (1UL << KASAN_SHADOW_SCALE_SHIFT) #define KASAN_SHADOW_MASK (KASAN_SHADOW_SCALE_SIZE - 1) +#define KHWASAN_TAG_KERNEL 0xFF /* native kernel pointers tag */ +#define KHWASAN_TAG_INVALID 0xFE /* inaccessible memory tag */ +#define KHWASAN_TAG_MAX 0xFD /* maximum value for random tags */ + #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 */ @@ -126,6 +130,57 @@ static inline void quarantine_reduce(void) { } static inline void quarantine_remove_cache(struct kmem_cache *cache) { } #endif +#ifdef CONFIG_KASAN_HW + +#define KHWASAN_TAG_SHIFT 56 +#define KHWASAN_TAG_MASK (0xFFUL << KHWASAN_TAG_SHIFT) + +u8 random_tag(void); + +static inline void *set_tag(const void *addr, u8 tag) +{ + u64 a = (u64)addr; + + a &= ~KHWASAN_TAG_MASK; + a |= ((u64)tag << KHWASAN_TAG_SHIFT); + + return (void *)a; +} + +static inline u8 get_tag(const void *addr) +{ + return (u8)((u64)addr >> KHWASAN_TAG_SHIFT); +} + +static inline void *reset_tag(const void *addr) +{ + return set_tag(addr, KHWASAN_TAG_KERNEL); +} + +#else /* CONFIG_KASAN_HW */ + +static inline u8 random_tag(void) +{ + return 0; +} + +static inline void *set_tag(const void *addr, u8 tag) +{ + return (void *)addr; +} + +static inline u8 get_tag(const void *addr) +{ + return 0; +} + +static inline void *reset_tag(const void *addr) +{ + return (void *)addr; +} + +#endif /* CONFIG_KASAN_HW */ + /* * Exported functions for interfaces called from assembly or from generated * code. Declarations here to avoid warning about missing declarations. diff --git a/mm/kasan/khwasan.c b/mm/kasan/khwasan.c index e2c3a7f7fd1f..d34679b8f8c7 100644 --- a/mm/kasan/khwasan.c +++ b/mm/kasan/khwasan.c @@ -38,6 +38,53 @@ #include "kasan.h" #include "../slab.h" +static DEFINE_PER_CPU(u32, prng_state); + +void khwasan_init(void) +{ + int cpu; + + for_each_possible_cpu(cpu) + per_cpu(prng_state, cpu) = get_random_u32(); +} + +/* + * If a preemption happens between this_cpu_read and this_cpu_write, the only + * side effect is that we'll give a few allocated in different contexts objects + * the same tag. Since KHWASAN is meant to be used a probabilistic bug-detection + * debug feature, this doesn’t have significant negative impact. + * + * Ideally the tags use strong randomness to prevent any attempts to predict + * them during explicit exploit attempts. But strong randomness is expensive, + * and we did an intentional trade-off to use a PRNG. This non-atomic RMW + * sequence has in fact positive effect, since interrupts that randomly skew + * PRNG at unpredictable points do only good. + */ +u8 random_tag(void) +{ + u32 state = this_cpu_read(prng_state); + + state = 1664525 * state + 1013904223; + this_cpu_write(prng_state, state); + + return (u8)(state % (KHWASAN_TAG_MAX + 1)); +} + +void *khwasan_set_tag(const void *addr, u8 tag) +{ + return set_tag(addr, tag); +} + +u8 khwasan_get_tag(const void *addr) +{ + return get_tag(addr); +} + +void *khwasan_reset_tag(const void *addr) +{ + return reset_tag(addr); +} + void check_memory_region(unsigned long addr, size_t size, bool write, unsigned long ret_ip) { -- 2.18.0.rc2.346.g013aa6912e-goog