From: Dave Chinner <david@fromorbit.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Dominique Martinet <asmadeus@codewreck.org>,
Jiri Kosina <jikos@kernel.org>,
Matthew Wilcox <willy@infradead.org>,
Jann Horn <jannh@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Greg KH <gregkh@linuxfoundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Michal Hocko <mhocko@suse.com>, Linux-MM <linux-mm@kvack.org>,
kernel list <linux-kernel@vger.kernel.org>,
Linux API <linux-api@vger.kernel.org>
Subject: Re: [PATCH] mm/mincore: allow for making sys_mincore() privileged
Date: Fri, 11 Jan 2019 18:36:06 +1100 [thread overview]
Message-ID: <20190111073606.GP27534@dastard> (raw)
In-Reply-To: <CAHk-=wh-kegfnPC_dmw0A72Sdk4B9tvce-cOR=jEfHDU1-4Eew@mail.gmail.com>
On Thu, Jan 10, 2019 at 11:08:07PM -0800, Linus Torvalds wrote:
> On Thu, Jan 10, 2019 at 8:04 PM Dave Chinner <david@fromorbit.com> wrote:
> >
> > So it will only read the single page we tried to access and won't
> > perturb the rest of the message encoded into subsequent pages in
> > file.
>
> Dave, you're being intentionally obtuse, aren't you?
>
> It's only that single page that *matters*. That's the page that the
> probe reveals the status of - but it's also the page that the probe
> then *changes* the status of.
It changes the state of it /after/ we've already got the information
we need from it. It's not up to date, it has to come from disk, we
return EAGAIN, which means it was not in the cache.
i.e. if we return EAGAIN, we've leaked the inforation the attacker
wants regardless of how the act of initiating readahead on the page
change the state of the page. Yes, it raises the complexity bar a
bit, and lowers the monitoring frequency somewhat, but that's about
it.
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2019-01-11 7:36 UTC|newest]
Thread overview: 161+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-05 17:27 [PATCH] mm/mincore: allow for making sys_mincore() privileged Jiri Kosina
2019-01-05 19:14 ` Vlastimil Babka
2019-01-05 19:24 ` Jiri Kosina
2019-01-05 19:38 ` Vlastimil Babka
2019-01-08 9:14 ` Bernd Petrovitsch
2019-01-08 11:37 ` Jiri Kosina
2019-01-08 13:53 ` Bernd Petrovitsch
2019-01-08 14:08 ` Kirill A. Shutemov
2019-01-05 19:44 ` kbuild test robot
2019-01-05 19:46 ` Linus Torvalds
2019-01-05 20:12 ` Jiri Kosina
2019-01-05 20:17 ` Linus Torvalds
2019-01-05 20:43 ` Jiri Kosina
2019-01-05 21:54 ` Linus Torvalds
2019-01-06 11:33 ` Kevin Easton
2019-01-08 8:50 ` Kevin Easton
2019-01-18 14:23 ` Tejun Heo
2019-01-05 20:13 ` Linus Torvalds
2019-01-05 19:56 ` kbuild test robot
2019-01-05 22:54 ` Jann Horn
2019-01-05 23:05 ` Linus Torvalds
2019-01-05 23:16 ` Linus Torvalds
2019-01-05 23:28 ` Linus Torvalds
2019-01-05 23:39 ` Linus Torvalds
2019-01-06 0:11 ` Matthew Wilcox
2019-01-06 0:22 ` Linus Torvalds
2019-01-06 1:50 ` Linus Torvalds
2019-01-06 21:46 ` Linus Torvalds
2019-01-08 4:43 ` Dave Chinner
2019-01-08 17:57 ` Linus Torvalds
2019-01-09 2:24 ` Dave Chinner
2019-01-09 2:31 ` Jiri Kosina
2019-01-09 4:39 ` Dave Chinner
2019-01-09 10:08 ` Jiri Kosina
2019-01-10 1:15 ` Dave Chinner
2019-01-10 7:54 ` Jiri Kosina
2019-01-09 18:25 ` Linus Torvalds
2019-01-10 0:44 ` Dave Chinner
2019-01-10 1:18 ` Linus Torvalds
2019-01-10 5:26 ` Andy Lutomirski
2019-01-10 14:47 ` Matthew Wilcox
2019-01-10 21:44 ` Dave Chinner
2019-01-10 21:59 ` Linus Torvalds
2019-01-11 1:47 ` Dave Chinner
2019-01-10 7:03 ` Dave Chinner
2019-01-10 11:47 ` Linus Torvalds
2019-01-10 12:24 ` Dominique Martinet
2019-01-10 22:11 ` Linus Torvalds
2019-01-11 2:03 ` Dave Chinner
2019-01-11 2:18 ` Linus Torvalds
2019-01-11 4:04 ` Dave Chinner
2019-01-11 4:08 ` Andy Lutomirski
2019-01-11 7:20 ` Dave Chinner
2019-01-11 7:08 ` Linus Torvalds
2019-01-11 7:36 ` Dave Chinner [this message]
2019-01-11 16:26 ` Linus Torvalds
2019-01-15 23:45 ` Dave Chinner
2019-01-16 4:54 ` Linus Torvalds
2019-01-16 5:49 ` Linus Torvalds
2019-01-17 1:26 ` Dave Chinner
2019-02-20 15:49 ` Nicolai Stange
2019-01-11 4:57 ` Dominique Martinet
2019-01-11 7:11 ` Linus Torvalds
2019-01-11 7:32 ` Dominique Martinet
2019-01-16 0:42 ` Josh Snyder
2019-01-16 5:00 ` Linus Torvalds
2019-01-16 5:25 ` Andy Lutomirski
2019-01-16 5:34 ` Linus Torvalds
2019-01-16 5:46 ` Dominique Martinet
2019-01-16 5:58 ` Linus Torvalds
2019-01-16 6:34 ` Dominique Martinet
2019-01-16 7:52 ` Josh Snyder
2019-01-16 12:18 ` Kevin Easton
2019-01-17 21:45 ` Vlastimil Babka
2019-01-18 4:49 ` Linus Torvalds
2019-01-18 18:58 ` Vlastimil Babka
2019-01-16 16:12 ` Jiri Kosina
2019-01-16 17:48 ` Linus Torvalds
2019-01-16 20:23 ` Jiri Kosina
2019-01-16 21:37 ` Matthew Wilcox
2019-01-16 21:41 ` Jiri Kosina
2019-01-17 9:52 ` Cyril Hrubis
2019-01-28 13:49 ` Cyril Hrubis
2019-01-17 4:51 ` Linus Torvalds
2019-01-18 4:54 ` Linus Torvalds
2019-01-17 1:49 ` Dominique Martinet
2019-01-23 20:27 ` Linus Torvalds
2019-01-23 20:35 ` Linus Torvalds
2019-01-23 23:12 ` Jiri Kosina
2019-01-24 0:20 ` Linus Torvalds
2019-01-24 0:24 ` Dominique Martinet
2019-01-24 12:45 ` Dominique Martinet
2019-01-24 14:25 ` Jiri Kosina
2019-01-27 22:35 ` Jiri Kosina
2019-01-28 0:05 ` Dominique Martinet
2019-01-29 23:52 ` Jiri Kosina
2019-01-30 9:09 ` Michal Hocko
2019-01-30 12:29 ` Jiri Kosina
2019-01-16 12:36 ` Matthew Wilcox
2019-01-10 14:50 ` Matthew Wilcox
2019-01-11 7:36 ` Jiri Kosina
2019-01-17 2:22 ` Dave Chinner
2019-01-17 8:18 ` Jiri Kosina
2019-01-17 21:06 ` Dave Chinner
2019-01-07 4:32 ` Dominique Martinet
2019-01-07 10:33 ` Vlastimil Babka
2019-01-07 11:08 ` Dominique Martinet
2019-01-07 11:59 ` Vlastimil Babka
2019-01-07 13:29 ` Daniel Gruss
2019-01-07 10:10 ` Michael Ellerman
2019-01-05 23:09 ` Jiri Kosina
2019-01-30 12:44 ` [PATCH 0/3] mincore() and IOCB_NOWAIT adjustments Vlastimil Babka
2019-01-30 12:44 ` [PATCH 1/3] mm/mincore: make mincore() more conservative Vlastimil Babka
2019-01-31 9:43 ` Michal Hocko
2019-01-31 9:51 ` Dominique Martinet
2019-01-31 17:46 ` Josh Snyder
2019-02-01 8:56 ` Vlastimil Babka
2019-03-06 23:13 ` Andrew Morton
2019-03-07 0:01 ` Jiri Kosina
2019-03-07 0:40 ` Dominique Martinet
2019-03-07 5:46 ` Jiri Kosina
2019-01-30 12:44 ` [PATCH 2/3] mm/filemap: initiate readahead even if IOCB_NOWAIT is set for the I/O Vlastimil Babka
2019-01-30 15:04 ` Florian Weimer
2019-01-30 15:15 ` Jiri Kosina
2019-01-31 10:47 ` Florian Weimer
2019-01-31 11:34 ` Jiri Kosina
2019-01-31 9:56 ` Michal Hocko
2019-01-31 10:15 ` Jiri Kosina
2019-01-31 10:23 ` Michal Hocko
2019-01-31 10:30 ` Jiri Kosina
2019-01-31 11:32 ` Michal Hocko
2019-01-31 17:54 ` Linus Torvalds
2019-02-01 5:13 ` Dave Chinner
2019-02-01 7:05 ` Linus Torvalds
2019-02-01 7:21 ` Linus Torvalds
2019-02-01 1:44 ` Dave Chinner
2019-02-12 15:48 ` Jiri Kosina
2019-01-31 12:04 ` Daniel Gruss
2019-01-31 12:06 ` Vlastimil Babka
2019-01-31 12:08 ` Jiri Kosina
2019-01-31 12:57 ` Daniel Gruss
2019-01-30 12:44 ` [PATCH 3/3] mm/mincore: provide mapped status when cached status is not allowed Vlastimil Babka
2019-01-31 10:09 ` Michal Hocko
2019-02-01 9:04 ` Vlastimil Babka
2019-02-01 9:11 ` Michal Hocko
2019-02-01 9:27 ` Vlastimil Babka
2019-02-06 20:14 ` Jiri Kosina
2019-02-12 3:44 ` Jiri Kosina
2019-02-12 6:36 ` Michal Hocko
2019-02-12 13:09 ` Jiri Kosina
2019-02-12 14:01 ` Michal Hocko
2019-03-06 12:11 ` [PATCH 0/3] mincore() and IOCB_NOWAIT adjustments Jiri Kosina
2019-03-06 22:35 ` Andrew Morton
2019-03-06 22:48 ` Jiri Kosina
2019-03-06 23:23 ` Andrew Morton
2019-03-06 23:32 ` Dominique Martinet
2019-03-06 23:38 ` Andrew Morton
2019-03-09 16:53 ` Linus Torvalds
2019-03-12 14:17 ` [PATCH v2 0/2] prevent mincore() page cache leaks Vlastimil Babka
2019-03-12 14:17 ` [PATCH v2 1/2] mm/mincore: make mincore() more conservative Vlastimil Babka
2019-03-12 14:17 ` [PATCH v2 2/2] mm/mincore: provide mapped status when cached status is not allowed Vlastimil Babka
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