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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id o70sm4127428pfo.33.2019.06.07.20.59.18 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 07 Jun 2019 20:59:19 -0700 (PDT) Date: Fri, 7 Jun 2019 20:59:18 -0700 From: Kees Cook To: Andrey Konovalov Cc: 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, Catalin Marinas , Vincenzo Frascino , Will Deacon , Mark Rutland , Andrew Morton , Greg Kroah-Hartman , 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 Subject: Re: [PATCH v16 06/16] mm, arm64: untag user pointers in mm/gup.c Message-ID: <201906072059.7D80BA0@keescook> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Mon, Jun 03, 2019 at 06:55:08PM +0200, 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. > > mm/gup.c provides a kernel interface that accepts user addresses and > manipulates user pages directly (for example get_user_pages, that is used > by the futex syscall). Since a user can provided tagged addresses, we need > to handle this case. > > Add untagging to gup.c functions that use user addresses for vma lookups. > > Reviewed-by: Catalin Marinas > Signed-off-by: Andrey Konovalov Reviewed-by: Kees Cook -Kees > --- > mm/gup.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/mm/gup.c b/mm/gup.c > index ddde097cf9e4..c37df3d455a2 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -802,6 +802,8 @@ static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, > if (!nr_pages) > return 0; > > + start = untagged_addr(start); > + > VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET)); > > /* > @@ -964,6 +966,8 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm, > struct vm_area_struct *vma; > vm_fault_t ret, major = 0; > > + address = untagged_addr(address); > + > if (unlocked) > fault_flags |= FAULT_FLAG_ALLOW_RETRY; > > -- > 2.22.0.rc1.311.g5d7573a151-goog > -- Kees Cook