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Shutemov" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Jens Axboe , Matthew Wilcox , Dennis Dalessandro , Leon Romanovsky , Christian Benvenuti , Nelson Escobar , Bernard Metzler , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Ian Rogers , Adrian Hunter , Bjorn Topel , Magnus Karlsson , Maciej Fijalkowski , Jonathan Lemon , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Christian Brauner , Richard Cochran , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , linux-fsdevel@vger.kernel.org, linux-perf-users@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, Oleg Nesterov , John Hubbard , Pavel Begunkov , Mika Penttila , David Hildenbrand , Dave Chinner , Theodore Ts'o , Peter Xu , Matthew Rosato , "Paul E . McKenney" , Christian Borntraeger Subject: Re: [PATCH v9 0/3] mm/gup: disallow GUP writing to file-backed mappings by default Message-ID: References: <20230515110315.uqifqgqkzcrrrubv@box.shutemov.name> <7f6dbe36-88f2-468e-83c1-c97e666d8317@lucifer.local> <20230517072920.bfs7gfo4whdmi6ay@quack3> <503e92f9-fbc2-422b-b0d4-f4cabe3f6802@lucifer.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <503e92f9-fbc2-422b-b0d4-f4cabe3f6802@lucifer.local> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: E70C02000C X-Stat-Signature: psda9wz4qfapwsmrhixohni88t6bd9y6 X-HE-Tag: 1684311022-774698 X-HE-Meta: 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 uyM9g7pm 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 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 Wed, May 17, 2023 at 08:55:27AM +0100, Lorenzo Stoakes wrote: > I'll try to take this in good faith because... yeah. I do get that, I mean > I literally created a repro for this situation and referenced in the commit > msg and comments this precise problem in my patch series that > addresses... this problem :P > > Perhaps I'm not being clear but it was simply my intent to highlight that > yes this is the primary problem but ALSO GUP writing to ostensibly 'clean' > pages 'behind the back' of a fs is _also_ a problem. Yes, it absolutely is a problem if that happens. But we can just fix it in the kernel using the: lock_page() copy data set_page_dirty_locked() unlock_page(); pattern, and we should have covere every place that did in tree. But there's no good way to verify it except for regular code audits.