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Mon, 24 Apr 2023 10:53:02 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.95) (envelope-from ) id 1pr0N2-001Vs1-FA; Mon, 24 Apr 2023 14:53:00 -0300 Date: Mon, 24 Apr 2023 14:53:00 -0300 From: Jason Gunthorpe To: Jan Kara Cc: Lorenzo Stoakes , 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, John Hubbard Subject: Re: [PATCH] mm/gup: disallow GUP writing to file-backed mappings by default Message-ID: References: <20230424160952.bvii2ahgxss2chev@quack3> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230424160952.bvii2ahgxss2chev@quack3> X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 27119A001F X-Rspam-User: X-Stat-Signature: ojsrpsqxgtbm3tu14s8h5jjpb75hryhf X-HE-Tag: 1682358783-4013 X-HE-Meta: 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 khp0QRse yPmCBOnOZh1Ah7Td0cdFt/rrFzDFB9k6if4k37IhY4W/5QiahfuNutNscAmMZPyFQS+ijQmRlN4uOUbG2QrDfl7KAXOQ7dk+3f1QIQjO4ki8l3DatKtzgERr7CwLXfiuWSiM9Q/zstqwwgEeyT1fpja2tUDIR1Vo9v+bVxEiFAO279n+Pqp5gBhBIXfzslQIrNFq3nNw0J+RESnQuCEE3lmifdllN/Yqu7x3w4ZvdIaoC5TWIIYl84f/XpXLn2gg6+mWclwrJ7KQSSAbGOpl7vE6gOMaGnhulogx390pYsUVswQglsUN87+PWuyDfLficquJDMQy953jhf7+wpTDNtS2jBVLYWGdKqs+qTRV1zTxSnD/7LNkRu/eEKwbP93SWxGXyLbWmHhMOfDJ2ivsFz7r58jpwCox9ORRr 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, Apr 24, 2023 at 06:09:52PM +0200, Jan Kara wrote: > So I'm maybe missing a bigger picture why we would like a change like this. > Because we still need to teach filesystems to handle pinned pages for the > usecases you don't forbid and for which we know there are users and then > what's the benefit of this patch? It immediately closes a security hole we have been talking about fixing for years already and still don't have a full fix for. An acknowledgment that this is not going to go away and starting to clamp down on the insecurity may motivate some investment in the proper fix. :) Jason