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[142.162.115.133]) by smtp.gmail.com with ESMTPSA id u65sm3796362qkb.58.2021.01.07.12.25.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 Jan 2021 12:25:25 -0800 (PST) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1kxbqX-003ua2-C3; Thu, 07 Jan 2021 16:25:25 -0400 Date: Thu, 7 Jan 2021 16:25:25 -0400 From: Jason Gunthorpe To: Andrea Arcangeli Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Yu Zhao , Andy Lutomirski , Peter Xu , Pavel Emelyanov , Mike Kravetz , Mike Rapoport , Minchan Kim , Will Deacon , Peter Zijlstra , Linus Torvalds , Hugh Dickins , "Kirill A. Shutemov" , Matthew Wilcox , Oleg Nesterov , Jann Horn , Kees Cook , John Hubbard , Leon Romanovsky , Jan Kara , Kirill Tkhai Subject: Re: [PATCH 0/2] page_count can't be used to decide when wp_page_copy Message-ID: <20210107202525.GD504133@ziepe.ca> References: <20210107200402.31095-1-aarcange@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210107200402.31095-1-aarcange@redhat.com> 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 Thu, Jan 07, 2021 at 03:04:00PM -0500, Andrea Arcangeli wrote: > vmsplice syscall API is insecure allowing long term GUP PINs without > privilege. Lots of places are relying on pin_user_pages long term pins of memory, and cannot be converted to notifiers. I don't think it is reasonable to just declare that insecure and requires privileges, it is a huge ABI break. FWIW, vhost tries to use notifiers as a replacement for GUP, and I think it ended up quite strange and complicated. It is hard to maintain performance when every access to the pages needs to hold some protection against parallel invalidation. Jason