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[209.85.167.48]) by smtp.gmail.com with ESMTPSA id p4sm2207983lfh.17.2020.12.21.12.26.38 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 21 Dec 2020 12:26:39 -0800 (PST) Received: by mail-lf1-f48.google.com with SMTP id o19so26809134lfo.1 for ; Mon, 21 Dec 2020 12:26:38 -0800 (PST) X-Received: by 2002:a05:6512:789:: with SMTP id x9mr6960312lfr.487.1608582398544; Mon, 21 Dec 2020 12:26:38 -0800 (PST) MIME-Version: 1.0 References: <20201219043006.2206347-1-namit@vmware.com> <20201221172711.GE6640@xz-x1> <76B4F49B-ED61-47EA-9BE4-7F17A26B610D@gmail.com> <9E301C7C-882A-4E0F-8D6D-1170E792065A@gmail.com> In-Reply-To: <9E301C7C-882A-4E0F-8D6D-1170E792065A@gmail.com> From: Linus Torvalds Date: Mon, 21 Dec 2020 12:26:22 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] mm/userfaultfd: fix memory corruption due to writeprotect To: Nadav Amit Cc: Yu Zhao , Peter Xu , Andrea Arcangeli , linux-mm , lkml , Pavel Emelyanov , Mike Kravetz , Mike Rapoport , stable , Minchan Kim , Andy Lutomirski , Will Deacon , Peter Zijlstra Content-Type: text/plain; charset="UTF-8" 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, Dec 21, 2020 at 12:23 PM Nadav Amit wrote: > > Using mmap_write_lock() was my initial fix and there was a strong pushback > on this approach due to its potential impact on performance. >From whom? Somebody who doesn't understand that correctness is more important than performance? And that userfaultfd is not the most important part of the system? The fact is, userfaultfd is CLEARLY BUGGY. Linus