From: "Eugene Teo" <eugeneteo@kernel.sg>
Subject: Re: [PATCH 4/4] ext3: Avoid printk floods in the face of directory corruption
Date: Thu, 18 Sep 2008 08:57:19 +0800
Message-ID: <28fa9c5e0809171757p59978419p810e7d0c571e33e6@mail.gmail.com>
References: <1221319971-29879-1-git-send-email-tytso@mit.edu>
	 <1221319971-29879-2-git-send-email-tytso@mit.edu>
	 <1221319971-29879-3-git-send-email-tytso@mit.edu>
	 <1221319971-29879-4-git-send-email-tytso@mit.edu>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
	"Eric Sandeen" <sandeen@redhat.com>, linux-ext4@vger.kernel.org
To: "Theodore Ts'o" <tytso@mit.edu>
In-Reply-To: <1221319971-29879-4-git-send-email-tytso@mit.edu>
Content-Disposition: inline
Sender: linux-ext4-owner@vger.kernel.org

On Sat, Sep 13, 2008 at 11:32 PM, Theodore Ts'o <tytso@mit.edu> wrote:
> Note: some people thinks this represents a security bug, since it
> might make the system go away while it is printing a large number of
> console messages, especially if a serial console is involved.  Hence,
> it has been assigned CVE-2008-3528, but it requires that the attacker
> either has physical access to your machine to insert a USB disk with a
> corrupted filesystem image (at which point why not just hit the power
> button), or is otherwise able to convince the system administrator to
> mount an arbitrary filesystem image (at which point why not just
> include a setuid shell or world-writable hard disk device file or some
> such).  Me, I think they're just being silly.

The description should explain what the problem is. And the last
sentence is a little ambiguous.

This is a user-triggerable DoS. The administrator who mounted the
filesystem image or partition might not know that the dir->i_size and
dir->i_blocks are corrupted. A remote user just need to perform either
a read or write operation to the mounted image or partition, and this
could trigger the problem, resulting in a denial of service.

Take note that another problem the test image shows is that, the
ext2/3 (and possibly ext4) filesystem does not honour the read-only
mode when the revision level is too high. That is, when
le32_to_cpu(es->s_rev_level) > EXT3_MAX_SUPP_REV. Eric replied me in a
private email that this is a different, and unrelated bug that will be
fixed.

Thanks, Eugene