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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=d+lRqXXla6mV/kMKnUzgl/DAB69C3QZUVHCf/SWSD4s=; b=Ys5Fm6hmDCah5IOaWsosx7JsC5d+WuKS+lsP5rJv7zej5nX8WqAUaHigao8LKhpd+9 xt+Kg8dEZWXyCccqM5oqxmKvq6A919F/SoEZ6I+8YuQ0aj5jWcL3lQ6YIk2b6zFXqs7q ElmN664ymwO4/JDQObBqD1IobtWgEOL3pbzMOMIpPWVQ3wi/dyts3bT70KkvcoCM27ab U5smk3/j3FqSZM+LaNzxXSmDlEtXjY4ssQZaTlTR5bzz4v8mhxG4Zk2TCMriG5tBUNfH srXIOCFGupIkvfObaNvSqILolYJlpq6JA5knXIAxJEDV6orhmUNnW9RhkAkjUpgllSzV Tv4w== X-Gm-Message-State: AOAM530uz6T6UMhQQZliROGJkVLrI9dPV9orYGGXEWo5WOAYbF+ambmC bRwslfzAWIkdAm6iFyxSb+wCEqnqxq8rj6El X-Google-Smtp-Source: ABdhPJx8+Oe7Mabnt4SPnvm3MnNRhLLp0Srowiy6PiObbMS1CIb56O1EYntDqekZUTCBtg9FLXBUbZu+17f2DcQW X-Received: from andreyknvl3.muc.corp.google.com ([2a00:79e0:15:13:7220:84ff:fe09:7e9d]) (user=andreyknvl job=sendgmr) by 2002:ad4:4870:: with SMTP id u16mr3018876qvy.44.1610554910673; Wed, 13 Jan 2021 08:21:50 -0800 (PST) Date: Wed, 13 Jan 2021 17:21:29 +0100 In-Reply-To: Message-Id: <1d82c593424e75ce15554a77e64794a75f8ed0c9.1610554432.git.andreyknvl@google.com> Mime-Version: 1.0 References: X-Mailer: git-send-email 2.30.0.284.gd98b1dd5eaa7-goog Subject: [PATCH v2 02/14] kasan: clarify HW_TAGS impact on TBI From: Andrey Konovalov To: Catalin Marinas , Vincenzo Frascino , Dmitry Vyukov , Alexander Potapenko , Marco Elver X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210113_112154_307552_7004FEF0 X-CRM114-Status: GOOD ( 12.29 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Branislav Rankov , Andrey Konovalov , Kevin Brodsky , Will Deacon , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, Andrey Ryabinin , Andrew Morton , Peter Collingbourne , Evgenii Stepanov Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Mention in the documentation that enabling CONFIG_KASAN_HW_TAGS always results in in-kernel TBI (Top Byte Ignore) being enabled. Also do a few minor documentation cleanups. Link: https://linux-review.googlesource.com/id/Iba2a6697e3c6304cb53f89ec61dedc77fa29e3ae Reviewed-by: Marco Elver Reviewed-by: Alexander Potapenko Signed-off-by: Andrey Konovalov --- Documentation/dev-tools/kasan.rst | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst index 0fc3fb1860c4..26c99852a852 100644 --- a/Documentation/dev-tools/kasan.rst +++ b/Documentation/dev-tools/kasan.rst @@ -147,15 +147,14 @@ negative values to distinguish between different kinds of inaccessible memory like redzones or freed memory (see mm/kasan/kasan.h). In the report above the arrows point to the shadow byte 03, which means that -the accessed address is partially accessible. - -For tag-based KASAN this last report section shows the memory tags around the -accessed address (see `Implementation details`_ section). +the accessed address is partially accessible. For tag-based KASAN modes this +last report section shows the memory tags around the accessed address +(see the `Implementation details`_ section). Boot parameters ~~~~~~~~~~~~~~~ -Hardware tag-based KASAN mode (see the section about different mode below) is +Hardware tag-based KASAN mode (see the section about various modes below) is intended for use in production as a security mitigation. Therefore it supports boot parameters that allow to disable KASAN competely or otherwise control particular KASAN features. @@ -305,6 +304,13 @@ reserved to tag freed memory regions. Hardware tag-based KASAN currently only supports tagging of kmem_cache_alloc/kmalloc and page_alloc memory. +If the hardware doesn't support MTE (pre ARMv8.5), hardware tag-based KASAN +won't be enabled. In this case all boot parameters are ignored. + +Note, that enabling CONFIG_KASAN_HW_TAGS always results in in-kernel TBI being +enabled. Even when kasan.mode=off is provided, or when the hardware doesn't +support MTE (but supports TBI). + What memory accesses are sanitised by KASAN? --------------------------------------------