netdev - Re: [PATCH v9 0/3] mm/gup: disallow GUP writing to file-backed mappings by default

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date: Wed, 17 May 2023 01:10:17 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Lorenzo Stoakes <lstoakes@...il.com>
Cc: Christoph Hellwig <hch@...radead.org>, Jan Kara <jack@...e.cz>,
	Jason Gunthorpe <jgg@...dia.com>,
	"Kirill A . Shutemov" <kirill@...temov.name>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jens Axboe <axboe@...nel.dk>, Matthew Wilcox <willy@...radead.org>,
	Dennis Dalessandro <dennis.dalessandro@...nelisnetworks.com>,
	Leon Romanovsky <leon@...nel.org>,
	Christian Benvenuti <benve@...co.com>,
	Nelson Escobar <neescoba@...co.com>,
	Bernard Metzler <bmt@...ich.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Bjorn Topel <bjorn@...nel.org>,
	Magnus Karlsson <magnus.karlsson@...el.com>,
	Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
	Jonathan Lemon <jonathan.lemon@...il.com>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Christian Brauner <brauner@...nel.org>,
	Richard Cochran <richardcochran@...il.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	linux-fsdevel@...r.kernel.org, linux-perf-users@...r.kernel.org,
	netdev@...r.kernel.org, bpf@...r.kernel.org,
	Oleg Nesterov <oleg@...hat.com>, John Hubbard <jhubbard@...dia.com>,
	Pavel Begunkov <asml.silence@...il.com>,
	Mika Penttila <mpenttil@...hat.com>,
	David Hildenbrand <david@...hat.com>,
	Dave Chinner <david@...morbit.com>, Theodore Ts'o <tytso@....edu>,
	Peter Xu <peterx@...hat.com>,
	Matthew Rosato <mjrosato@...ux.ibm.com>,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Christian Borntraeger <borntraeger@...ux.ibm.com>
Subject: Re: [PATCH v9 0/3] mm/gup: disallow GUP writing to file-backed
 mappings by default

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.