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Date: Wed, 27 Apr 2011 11:00:16 -0400
From: Dan Rosenberg <dan.j.rosenberg@...il.com>
To: Tomas Hoger <thoger@...hat.com>
Cc: oss-security@...ts.openwall.com, Ludwig Nussel <ludwig.nussel@...e.de>, 
	Petr Baudis <pasky@...e.cz>
Subject: Re: Suid mount helpers fail to anticipate RLIMIT_FSIZE

On Wed, Apr 27, 2011 at 10:56 AM, Tomas Hoger <thoger@...hat.com> wrote:
> On Tue, 15 Mar 2011 09:13:00 -0400 Dan Rosenberg wrote:
>
>> util-linux mount
>> =============
>> * Edits /etc/mtab.tmp with custom my_addmntent(), behaves identically
>> to glibc addmntent() in terms of return code
>> * Succeeds on partial writes, does not remove temp file on failure
>> (could result in additional corruption of /etc/mtab through multiple
>> invocations), does not remove lock file /etc/mtab~ on failure (also an
>> issue)
>
> Dan, would you mind clarifying the way to achieve mtab corruption via
> truncated left-over mtab.tmp file and multiple invocations?  After some
> discussion with our util-linux maintainer, we fail to see an obvious
> way.  util-linux opens mtab.tmp using "w" fopen open, i.e. using O_TRUNC
> open flag.  So if there's any mtab.tmp file found, it's overwritten and
> its existence does not block further use of mount / umount as existence
> of mtab~ lock file does.
>

Ah, quite right.  I missed that since I was just doing a quick survey
of a bunch of helpers.  It seems the mtab.tmp file isn't an issue.
Thanks for looking into it.

-Dan

> Thank you!
>
> --
> Tomas Hoger / Red Hat Security Response Team
>

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