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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=VRs7dAB+P//KjkP9Cahy8mQRvB3cL9kKzxtAOErS7Qw=; b=LFbApK/pA94hAiEcXbYrJF3sQy/ItAKzoj6Ktsiw9XQt5InrJcPmsTX+ikgbXNjNHE QENHxB/YbLcHngNUY3E7MImaev1V08XrU0bBNRNSqKNMfpMkvuGNi4VeWnsxJrI1QFmd tZ4Od87MhHnyzKGcSkmVUmElfcR3OkHdvgtMIhNV2mw93ageft6gcBvZbWAFbmBh1LGD dvZcy+Yh7q1hfosK/WAzPtacNkGB3EtoMCDgCJYjp4U0MtRq4g4Smbqm4KDjUY+hsqEJ KY1kMkfmAunHZlTlSCwSxKyveZcPrnDmMn+HrndYp3jM8CEqCJgJ1vvFSEkzhc4ySpw3 8lLw== X-Gm-Message-State: AOAM533R4e/ojUIUSVWu0A9swOfciNr3SpcT6uBR4LtDyrIONhMQoVhV ZKvlpCvT/QrpoBYYsp4dbHezwH89kWfaT/WH X-Google-Smtp-Source: ABdhPJxs7jsjH84m07SSwoqwOtTTJLJPT0usU1rxQ6d4O9vZHQndB+TM03WuWDwAEbVn2jHGgQ6EAgLEVWCFhVAp X-Received: from andreyknvl3.muc.corp.google.com ([2a00:79e0:15:13:7220:84ff:fe09:7e9d]) (user=andreyknvl job=sendgmr) by 2002:a05:6214:684:: with SMTP id r4mr745500qvz.54.1609871287214; Tue, 05 Jan 2021 10:28:07 -0800 (PST) Date: Tue, 5 Jan 2021 19:27:46 +0100 In-Reply-To: Message-Id: Mime-Version: 1.0 References: X-Mailer: git-send-email 2.29.2.729.g45daf8777d-goog Subject: [PATCH 02/11] 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-20210105_132811_064842_1B38DD2F X-CRM114-Status: GOOD ( 12.02 ) 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 , 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. Signed-off-by: Andrey Konovalov Link: https://linux-review.googlesource.com/id/Iba2a6697e3c6304cb53f89ec61dedc77fa29e3ae Reviewed-by: Alexander Potapenko Reviewed-by: Marco Elver --- 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? --------------------------------------------