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Date: Thu, 31 Mar 2016 17:37:19 +0200 (CEST)
From: "Hugues ANGUELKOV" <hugues.anguelkov@....univ-nantes.fr>
To: tytso@...ena.mit.edu
Cc: kseifried@...hat.com,
 sandeen@...hat.com,
 oss-security@...ts.openwall.com
Subject: Re: CVE Request - Linux kernel (multiple versions) ext2/ext3 
     filesystem DoS

Date: Thu, 31 Mar 2016 08:53:17 -0600
From: Kurt Seifried <kseifried@...hat.com>
To: oss-security <oss-security@...ts.openwall.com>
Cc: Andreas Dilger <adilger@...ger.ca>, Yves-Alexis Perez
<corsac@...ian.org>,
	Theodore Tso <tytso@...gle.com>, linux-ext4@...r.kernel.org
Subject: Re: CVE Request - Linux kernel (multiple versions)
 ext2/ext3 filesystem DoS

On Wed, Mar 30, 2016 at 2:43 PM, Theodore Ts'o <tytso@....edu> wrote:
>
>
> You can mount the file system with "mount -o errors=continue" and this
> will override the default behavior specified in the super block.
>
> I would argue that a Desktop or server system that had automount
> should either (a) mount with -o errors=continue, or (b) force an fsck
> on the file system before mounting it.
>

The problem is that:

a) means I'll be mounting filesystems with errors that I may want to know
about (but not have my  system panic about)

b) fsck takes a long time on large disks (the smallest size of disk I buy
for USB drives is 1TB, if I fsck every time I plug one in I'll die of old
age).


>
> So I think this is a particularly meaningless CVE, which is why I have
> zero respect for people who try to make any kind of conclusion based
> on CVE counts.   I certainly don't plan to do anything about this.
>

As for your comments on CVE counting even the then head of CVE @mitre told
people not to rely on CVE counting for vulnerability stats:

https://media.blackhat.com/us-13/US-13-Martin-Buying-Into-The-Bias-Why-Vulnerability-Statistics-Suck-Slides.pdf

As for your comment on not fixing this: I think fundamentally I should be
able to plug a file system in and try to mount it with default/reasonable
options and NOT have my system panic. File system handling code, like any
code that handles user supplied data should be able to handle garbage
gracefully and securely. At worst it should try to mount and go "derp, it's
messed up, maybe fsck it?"



>
>                                            - Ted
>


First of all, I would like to say I'm not a MIT genius nor a security
engineer, just a chemistry student who were fuzzing his box on his free
time. I'm not interested about getting CVE nor collecting them and I
apologize if my mail have sound like that.
I was just concerned about getting a better system where I can mount any
file system without any crash/panic.
But again I'm not a pro/engineer, and I know that I've got no credibility
and it's certainly not with these kind of things I will get somes. Anyway,
thanks for reading and all your work, now I'm gonna use this fucking DoS
trick called "shutdown -h now" and stop reporting thing what I was
thinking it was strange behaviour.
Hugues.

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