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[209.85.167.49]) by smtp.gmail.com with ESMTPSA id s19sm2280170lfc.41.2020.12.21.15.33.46 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 21 Dec 2020 15:33:47 -0800 (PST) Received: by mail-lf1-f49.google.com with SMTP id h205so27715381lfd.5 for ; Mon, 21 Dec 2020 15:33:46 -0800 (PST) X-Received: by 2002:a05:6512:338f:: with SMTP id h15mr7192658lfg.40.1608593626453; Mon, 21 Dec 2020 15:33:46 -0800 (PST) MIME-Version: 1.0 References: <20201221172711.GE6640@xz-x1> <76B4F49B-ED61-47EA-9BE4-7F17A26B610D@gmail.com> <9E301C7C-882A-4E0F-8D6D-1170E792065A@gmail.com> <1FCC8F93-FF29-44D3-A73A-DF943D056680@gmail.com> <20201221223041.GL6640@xz-x1> In-Reply-To: From: Linus Torvalds Date: Mon, 21 Dec 2020 15:33:30 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] mm/userfaultfd: fix memory corruption due to writeprotect To: Yu Zhao Cc: Peter Xu , Nadav Amit , 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 3:12 PM Yu Zhao wrote: > > I can't say I disagree with you but the man has made the call and I > think we should just move on. "The man" can always be convinced by numbers. So if somebody comes up with an alternate patch, and explains it, and shows that it is better - go for it. I just think that if mprotect() can take the mmap lock for writing, then userfaultfd sure as hell can. What odd load does people have where userfaultfd is more important than mprotect? So as far as the man is concerned, I think "just fix userfaultfd" is simply the default obvious operation. Not necessarily a final endpoint. Linus