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[217.140.110.172]) by mx.google.com with ESMTP id g23si65500eje.302.2019.06.12.07.35.33 for ; Wed, 12 Jun 2019 07:35:34 -0700 (PDT) Received-SPF: pass (google.com: domain of vincenzo.frascino@arm.com designates 217.140.110.172 as permitted sender) client-ip=217.140.110.172; Authentication-Results: mx.google.com; spf=pass (google.com: domain of vincenzo.frascino@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=vincenzo.frascino@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 2A2822B; Wed, 12 Jun 2019 07:35:33 -0700 (PDT) Received: from [10.1.196.72] (e119884-lin.cambridge.arm.com [10.1.196.72]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1FAE33F557; Wed, 12 Jun 2019 07:35:27 -0700 (PDT) Subject: Re: [PATCH v17 07/15] fs, arm64: untag user pointers in copy_mount_options To: Andrey Konovalov , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org Cc: Catalin Marinas , Will Deacon , Mark Rutland , Andrew Morton , Greg Kroah-Hartman , Kees Cook , Yishai Hadas , Felix Kuehling , Alexander Deucher , Christian Koenig , Mauro Carvalho Chehab , Jens Wiklander , Alex Williamson , Leon Romanovsky , Luc Van Oostenryck , Dave Martin , Khalid Aziz , enh , Jason Gunthorpe , Christoph Hellwig , Dmitry Vyukov , Kostya Serebryany , Evgeniy Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Robin Murphy , Kevin Brodsky , Szabolcs Nagy References: <4ed871e14cc265a519c6ba8660a1827844371791.1560339705.git.andreyknvl@google.com> From: Vincenzo Frascino Message-ID: <4a70a119-e40d-3fa3-8426-ba946e1af76a@arm.com> Date: Wed, 12 Jun 2019 15:35:27 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <4ed871e14cc265a519c6ba8660a1827844371791.1560339705.git.andreyknvl@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 12/06/2019 12:43, Andrey Konovalov wrote: > This patch is a part of a series that extends arm64 kernel ABI to allow to > pass tagged user pointers (with the top byte set to something else other > than 0x00) as syscall arguments. > > In copy_mount_options a user address is being subtracted from TASK_SIZE. > If the address is lower than TASK_SIZE, the size is calculated to not > allow the exact_copy_from_user() call to cross TASK_SIZE boundary. > However if the address is tagged, then the size will be calculated > incorrectly. > > Untag the address before subtracting. > > Reviewed-by: Kees Cook > Reviewed-by: Catalin Marinas > Signed-off-by: Andrey Konovalov Reviewed-by: Vincenzo Frascino > --- > fs/namespace.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/namespace.c b/fs/namespace.c > index b26778bdc236..2e85712a19ed 100644 > --- a/fs/namespace.c > +++ b/fs/namespace.c > @@ -2993,7 +2993,7 @@ void *copy_mount_options(const void __user * data) > * the remainder of the page. > */ > /* copy_from_user cannot cross TASK_SIZE ! */ > - size = TASK_SIZE - (unsigned long)data; > + size = TASK_SIZE - (unsigned long)untagged_addr(data); > if (size > PAGE_SIZE) > size = PAGE_SIZE; > > -- Regards, Vincenzo