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[209.85.221.54]) by smtp.gmail.com with ESMTPSA id 35sm3143348ede.0.2021.01.07.14.48.26 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 07 Jan 2021 14:48:26 -0800 (PST) Received: by mail-wr1-f54.google.com with SMTP id q18so7194745wrn.1 for ; Thu, 07 Jan 2021 14:48:26 -0800 (PST) X-Received: by 2002:a05:6512:789:: with SMTP id x9mr348260lfr.487.1610059353457; Thu, 07 Jan 2021 14:42:33 -0800 (PST) MIME-Version: 1.0 References: <20210107200402.31095-1-aarcange@redhat.com> <20210107200402.31095-3-aarcange@redhat.com> In-Reply-To: From: Linus Torvalds Date: Thu, 7 Jan 2021 14:42:17 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 2/2] mm: soft_dirty: userfaultfd: introduce wrprotect_tlb_flush_pending To: Andrea Arcangeli Cc: Linux-MM , Linux Kernel Mailing List , Yu Zhao , Andy Lutomirski , Peter Xu , Pavel Emelyanov , Mike Kravetz , Mike Rapoport , Minchan Kim , Will Deacon , Peter Zijlstra , Hugh Dickins , "Kirill A. Shutemov" , Matthew Wilcox , Oleg Nesterov , Jann Horn , Kees Cook , John Hubbard , Leon Romanovsky , Jason Gunthorpe , Jan Kara , Kirill Tkhai 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 Thu, Jan 7, 2021 at 2:31 PM Andrea Arcangeli wrote: > > Random memory corruption will still silently materialize as result of > the speculative lookups in the above scenario. Explain. Yes, you'll get random memory corruption if you keep doing wrprotect() without mmap_sem held for writing. But I thought we agreed earlier that that is a bug. And I thought the softdirty code already got it for writing. Linus