linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Pavel Machek <pavel@ucw.cz>
To: "Theodore Y. Ts'o" <tytso@mit.edu>
Cc: Josh Triplett <josh@joshtriplett.org>,
	"Darrick J. Wong" <darrick.wong@oracle.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andreas Dilger <adilger.kernel@dilger.ca>,
	Jan Kara <jack@suse.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-ext4@vger.kernel.org
Subject: Malicious fs images was Re: ext4 regression in v5.9-rc2 from e7bfb5c9bb3d on ro fs with overlapped bitmaps
Date: Sun, 10 Jan 2021 19:41:02 +0100	[thread overview]
Message-ID: <20210110184101.GA4625@amd> (raw)
In-Reply-To: <20201009143732.GJ235506@mit.edu>

[-- Attachment #1: Type: text/plain, Size: 2071 bytes --]

Hi!

On Fri 2020-10-09 10:37:32, Theodore Y. Ts'o wrote:
> On Thu, Oct 08, 2020 at 03:22:59PM -0700, Josh Triplett wrote:
> > 
> > I wasn't trying to make a *new* general principle or policy. I was under
> > the impression that this *was* the policy, because it never occurred to
> > me that it could be otherwise. It seemed like a natural aspect of the
> > kernel/userspace boundary, to the point that the idea of it *not* being
> > part of the kernel's stability guarantees didn't cross my mind. 
> 
> >From our perspective (and Darrick and I discussed this on this week's
> ext4 video conference, so it represents the ext4 and xfs maintainer's
> position) is that the file system format is different.  First, the
> on-disk format is not an ABI, and it is several orders more complex
> than a system call interface.  Second, we make no guarantees about
> what the file system created by malicious tools will do.  For example,
> XFS developers reject bug reports from file system fuzzers, because
> the v5 format has CRC checks, so randomly corrupted file systems won't
> crash the kernel.  Yes, this doesn't protect against maliciously
> created file systems where the attacker makes sure the checksums are
> valid, but only crazy people who think containers are just as secure

Well, it is not just containers. It is also USB sticks. And people who
believe secure boot is good idea and try to protect kernel against
root. And crazy people who encrypt pointers in dmesg. And...

People want to use USB sticks from time to time. And while I
understand XFS is so complex it is unsuitable for such use, I'd still
expect bugs to be fixed there.

I hope VFAT to be safe to mount, because that is very common on USB.

I also hope ext2/3/4 is safe in that regard.

Anyway it would be nice to have documentation explaining this. If I'm
wrong about VFAT being safe, it would be good to know, and I guess
many will be surprised that XFS is using different rules.

Best regards,
								Pavel
-- 
http://www.livejournal.com/~pavelmachek

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 181 bytes --]

  parent reply	other threads:[~2021-01-10 18:42 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-04 23:17 Linux 5.9-rc8 Linus Torvalds
2020-10-05  8:14 ` ext4 regression in v5.9-rc2 from e7bfb5c9bb3d on ro fs with overlapped bitmaps Josh Triplett
2020-10-05  9:46   ` Jan Kara
2020-10-05 10:16     ` Josh Triplett
2020-10-05 16:19       ` Jan Kara
2020-10-05 16:20   ` Jan Kara
2020-10-05 17:36   ` Darrick J. Wong
2020-10-06  0:04     ` Theodore Y. Ts'o
2020-10-06  0:32     ` Josh Triplett
2020-10-06  2:51       ` Darrick J. Wong
2020-10-06  3:18         ` Theodore Y. Ts'o
2020-10-06  5:03           ` Josh Triplett
2020-10-06  6:03             ` Josh Triplett
2020-10-06 13:35             ` Theodore Y. Ts'o
2020-10-07  8:03               ` Josh Triplett
2020-10-07 14:32                 ` Theodore Y. Ts'o
2020-10-07 20:14                   ` Josh Triplett
2020-10-08  2:10                     ` Theodore Y. Ts'o
2020-10-08 17:54                       ` Darrick J. Wong
2020-10-08 22:38                         ` Josh Triplett
2020-10-09  2:54                           ` Darrick J. Wong
2020-10-09 19:08                             ` Josh Triplett
2020-10-08 22:22                       ` Josh Triplett
2020-10-09 14:37                         ` Theodore Y. Ts'o
2020-10-09 20:30                           ` Josh Triplett
2021-01-10 18:41                           ` Pavel Machek [this message]
2021-01-11 18:51                             ` Malicious fs images was " Darrick J. Wong
2021-01-11 19:39                               ` Eric Biggers
2021-01-12 21:43                             ` Theodore Ts'o
2021-01-12 22:28                               ` Pavel Machek
2021-01-13  5:09                                 ` Theodore Ts'o
2020-10-08  2:57                     ` Andreas Dilger
2020-10-08 19:12                       ` Josh Triplett
2020-10-08 19:25                         ` Andreas Dilger
2020-10-08 22:28                           ` Josh Triplett

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210110184101.GA4625@amd \
    --to=pavel@ucw.cz \
    --cc=adilger.kernel@dilger.ca \
    --cc=darrick.wong@oracle.com \
    --cc=jack@suse.com \
    --cc=josh@joshtriplett.org \
    --cc=linux-ext4@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=torvalds@linux-foundation.org \
    --cc=tytso@mit.edu \
    --subject='Malicious fs images was Re: ext4 regression in v5.9-rc2 from e7bfb5c9bb3d on ro fs with overlapped bitmaps' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
on how to clone and mirror all data and code used for this inbox