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[217.140.101.70]) by mx.google.com with ESMTP id v20si602306edm.292.2019.03.01.08.59.16 for ; Fri, 01 Mar 2019 08:59:16 -0800 (PST) Received-SPF: pass (google.com: domain of catalin.marinas@arm.com designates 217.140.101.70 as permitted sender) client-ip=217.140.101.70; Authentication-Results: mx.google.com; spf=pass (google.com: domain of catalin.marinas@arm.com designates 217.140.101.70 as permitted sender) smtp.mailfrom=catalin.marinas@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D6B7080D; Fri, 1 Mar 2019 08:59:15 -0800 (PST) Received: from arrakis.emea.arm.com (arrakis.cambridge.arm.com [10.1.196.78]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0CD8F3F575; Fri, 1 Mar 2019 08:59:10 -0800 (PST) Date: Fri, 1 Mar 2019 16:59:08 +0000 From: Catalin Marinas To: Andrey Konovalov Cc: Dave Hansen , Will Deacon , Mark Rutland , Robin Murphy , Kees Cook , Kate Stewart , Greg Kroah-Hartman , Andrew Morton , Ingo Molnar , "Kirill A . Shutemov" , Shuah Khan , Vincenzo Frascino , Linux ARM , "open list:DOCUMENTATION" , Linux Memory Management List , linux-arch , "open list:KERNEL SELFTEST FRAMEWORK" , LKML , Dmitry Vyukov , Kostya Serebryany , Evgeniy Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Chintan Pandya , Luc Van Oostenryck , Dave Martin , Kevin Brodsky , Szabolcs Nagy Subject: Re: [PATCH v10 07/12] fs, arm64: untag user pointers in fs/userfaultfd.c Message-ID: <20190301165908.GA130541@arrakis.emea.arm.com> References: <8343cd77ca301df15839796f3b446b75ce5ffbbf.1550839937.git.andreyknvl@google.com> <73f2f3fe-9a66-22a1-5aae-c282779a75f5@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) 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 Tue, Feb 26, 2019 at 03:39:08PM +0100, Andrey Konovalov wrote: > On Sat, Feb 23, 2019 at 12:06 AM Dave Hansen wrote: > > > > On 2/22/19 4:53 AM, Andrey Konovalov wrote: > > > userfaultfd_register() and userfaultfd_unregister() use provided user > > > pointers for vma lookups, which can only by done with untagged pointers. > > > > So, we have to patch all these sites before the tagged values get to the > > point of hitting the vma lookup functions. Dumb question: Why don't we > > just patch the vma lookup functions themselves instead of all of these > > callers? > > That might be a working approach as well. We'll still need to fix up > places where the vma fields are accessed directly. Catalin, what do > you think? Most callers of find_vma*() always follow it by a check of vma->vma_start against some tagged address ('end' in the userfaultfd_(un)register()) case. So it's not sufficient to untag it in find_vma(). -- Catalin