From patchwork Wed Sep 19 18:54:47 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Andrey Konovalov X-Patchwork-Id: 10606317 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 762896CB for ; Wed, 19 Sep 2018 18:57:17 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 69735274A3 for ; Wed, 19 Sep 2018 18:57:17 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 5C179284A5; Wed, 19 Sep 2018 18:57:17 +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 DA27A274A3 for ; Wed, 19 Sep 2018 18:57:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387513AbeITAed (ORCPT ); Wed, 19 Sep 2018 20:34:33 -0400 Received: from mail-wm1-f67.google.com ([209.85.128.67]:38351 "EHLO mail-wm1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387477AbeITAec (ORCPT ); Wed, 19 Sep 2018 20:34:32 -0400 Received: by mail-wm1-f67.google.com with SMTP id t25-v6so8137136wmi.3 for ; Wed, 19 Sep 2018 11:55:17 -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=MFWmZ2ymGw7SFNCT+sDf2yM6FOtMRHS5/lhwAKyi41M=; b=IqYYK6SU9pnRTgV15qs62JcLXf/m3ATgrjIeRvDfbSFBDxyovt3Dm4Lg786w5AseU5 Mae0w7RS8HUuPeA7f+uXCK1rM0x4/jv0+9M9dFUdiLqu62wpofAN28FjvVPhPK6chlvJ e45Vw6cbLFf1HeO4sgAnOyP5eiI74zXKJGiOuKPsiGQNlGkI7gdTwl1TygXQGf+I+wM1 a96JjD6bXs2c0ZNGqaIWn7CA75MiAsSV1e66KOMRFmquPJIgKpK9LrCcqz8KQjLDp4Uj 4l8Pi9agIB2MUaOjJcbdQbH+95GpX9EV2HsxGT9AKOGujouVX+qFVKm1V5f40rPIlZXs kNaw== 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=MFWmZ2ymGw7SFNCT+sDf2yM6FOtMRHS5/lhwAKyi41M=; b=iOzDxd7MNB8KZ9xH09PKa+cIdzvpnXoPfl7psIIpL87FDjVNzcXPikWBuuJsl2gDLI aN1ChoDU3GnYLJMqsh6gxa31sFu8jNnrznXGeNlZ+3sUD6YOsZkuCp6bZMwW1pupVwTq Fppp3/AXGHDjPoc1i2dHqaqmqjlD6aZ5PNwgosVr6IsvY+J44NrQ+JKz+dExK/i1h72E ZGZVv8tzPd377aaVOTSM/vAC/OgbSxP5f1ZPbn/W8O+EUmkZy4kooTRteF6C6eRcLPjr /x7mPBQkeEconnUjTis3gONrr/v0CHgszLyuBTje2oaMSh5yikbd5kgWIgu92+vdEujC P49A== X-Gm-Message-State: APzg51BCM+8/hcgMgV/kAaY3IFzqg7W/1pWvT18uwD/1ywAQ+DeagKLf CDxLwnXnAiS3ba9IkBPT06oBSA== X-Google-Smtp-Source: ANB0VdbYUdT1KRAy58Mt7lu/XViex7l4kcxG8+LuGI0hRyyJeq/zNg/WgbiXvKSO+4udIQquLyu5aQ== X-Received: by 2002:a1c:9290:: with SMTP id u138-v6mr21163466wmd.52.1537383316609; Wed, 19 Sep 2018 11:55:16 -0700 (PDT) Received: from andreyknvl0.muc.corp.google.com ([2a00:79e0:15:10:84be:a42a:826d:c530]) by smtp.gmail.com with ESMTPSA id b10-v6sm8510065wmc.28.2018.09.19.11.55.15 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 19 Sep 2018 11:55:16 -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 , Vishwath Mohan , Andrey Konovalov Subject: [PATCH v8 08/20] kasan: add tag related helper functions Date: Wed, 19 Sep 2018 20:54:47 +0200 Message-Id: <79532ad7be1a40637e6646eb0ada6195974df503.1537383101.git.andreyknvl@google.com> X-Mailer: git-send-email 2.19.0.397.gdd90340f6a-goog In-Reply-To: References: MIME-Version: 1.0 Sender: linux-kbuild-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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 | 13 +++++++++ mm/kasan/kasan.h | 55 ++++++++++++++++++++++++++++++++++++++ mm/kasan/tags.c | 37 +++++++++++++++++++++++++ 4 files changed, 107 insertions(+) diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c index 7a31e8ccbad2..ecd3f25cc323 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)); + kasan_init_tags(); + /* 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 e7162ca9d66b..7e5be87a05b3 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -169,6 +169,19 @@ static inline void kasan_cache_shutdown(struct kmem_cache *cache) {} #define KASAN_SHADOW_INIT 0xFF +void kasan_init_tags(void); + +void *kasan_reset_tag(const void *addr); + +#else /* CONFIG_KASAN_SW_TAGS */ + +static inline void kasan_init_tags(void) { } + +static inline void *kasan_reset_tag(const void *addr) +{ + return (void *)addr; +} + #endif /* CONFIG_KASAN_SW_TAGS */ #endif /* LINUX_KASAN_H */ diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index 19b950eaccff..63ab9775275b 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 KASAN_TAG_KERNEL 0xFF /* native kernel pointers tag */ +#define KASAN_TAG_INVALID 0xFE /* inaccessible memory tag */ +#define KASAN_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_SW_TAGS + +#define KASAN_TAG_SHIFT 56 +#define KASAN_TAG_MASK (0xFFUL << KASAN_TAG_SHIFT) + +u8 random_tag(void); + +static inline void *set_tag(const void *addr, u8 tag) +{ + u64 a = (u64)addr; + + a &= ~KASAN_TAG_MASK; + a |= ((u64)tag << KASAN_TAG_SHIFT); + + return (void *)a; +} + +static inline u8 get_tag(const void *addr) +{ + return (u8)((u64)addr >> KASAN_TAG_SHIFT); +} + +static inline void *reset_tag(const void *addr) +{ + return set_tag(addr, KASAN_TAG_KERNEL); +} + +#else /* CONFIG_KASAN_SW_TAGS */ + +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_SW_TAGS */ + /* * Exported functions for interfaces called from assembly or from generated * code. Declarations here to avoid warning about missing declarations. diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c index 04194923c543..700323946867 100644 --- a/mm/kasan/tags.c +++ b/mm/kasan/tags.c @@ -38,6 +38,43 @@ #include "kasan.h" #include "../slab.h" +static DEFINE_PER_CPU(u32, prng_state); + +void kasan_init_tags(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 tag-based KASAN 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 % (KASAN_TAG_MAX + 1)); +} + +void *kasan_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) {