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Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kduuJ-0005KL-DW; Sat, 14 Nov 2020 12:43:55 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kduuG-0005Jm-5M for linux-arm-kernel@lists.infradead.org; Sat, 14 Nov 2020 12:43:52 +0000 Received: from gaia (unknown [2.26.170.190]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1FFF720759; Sat, 14 Nov 2020 12:43:48 +0000 (UTC) Date: Sat, 14 Nov 2020 12:43:46 +0000 From: Catalin Marinas To: Andrey Konovalov Subject: Re: [PATCH mm v10 26/42] arm64: mte: Reset the page tag in page->flags Message-ID: <20201114124346.GC2837@gaia> References: <18bca1ff61bf6605289e7213153b3fd5b8f81e27.1605305705.git.andreyknvl@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <18bca1ff61bf6605289e7213153b3fd5b8f81e27.1605305705.git.andreyknvl@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201114_074352_322956_9741396B X-CRM114-Status: GOOD ( 16.92 ) 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: linux-arm-kernel@lists.infradead.org, Marco Elver , Kevin Brodsky , Will Deacon , Branislav Rankov , kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Alexander Potapenko , Evgenii Stepanov , Andrey Ryabinin , Andrew Morton , Vincenzo Frascino , Dmitry Vyukov Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Nov 13, 2020 at 11:15:54PM +0100, Andrey Konovalov wrote: > From: Vincenzo Frascino > > The hardware tag-based KASAN for compatibility with the other modes > stores the tag associated to a page in page->flags. > Due to this the kernel faults on access when it allocates a page with an > initial tag and the user changes the tags. > > Reset the tag associated by the kernel to a page in all the meaningful > places to prevent kernel faults on access. > > Note: An alternative to this approach could be to modify page_to_virt(). > This though could end up being racy, in fact if a CPU checks the > PG_mte_tagged bit and decides that the page is not tagged but another > CPU maps the same with PROT_MTE and becomes tagged the subsequent kernel > access would fail. > > Signed-off-by: Vincenzo Frascino > Signed-off-by: Andrey Konovalov Reviewed-by: Catalin Marinas _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel