linux-ext4 - Re: [PATCH 1/3] ext4: sanity check the block and cluster size at mount time

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Date:   Fri, 18 Nov 2016 12:58:39 -0500
From:   Theodore Ts'o <tytso@....edu>
To:     Nikolay Borisov <kernel@...p.com>
Cc:     Ext4 Developers List <linux-ext4@...r.kernel.org>, bp@...en8.de,
        stable@...r.kernel.org
Subject: Re: [PATCH 1/3] ext4: sanity check the block and cluster size at
 mount time

On Fri, Nov 18, 2016 at 09:40:02AM +0200, Nikolay Borisov wrote:
> 
> 
> On 11/18/2016 06:26 AM, Theodore Ts'o wrote:
> > If the block size or cluster size is insane, reject the mount.  This
> > is important for security reasons (although we shouldn't be just
> > depending on this check).
> > 
> > Ref: http://www.securityfocus.com/archive/1/539661
> > Ref: https://bugzilla.redhat.com/show_bug.cgi?id=1332506
> > Reported-by: Borislav Petkov <bp@...en8.de>
> > Reported-by: Nikolay Borisov <kernel@...p.com>
> > Signed-off-by: Theodore Ts'o <tytso@....edu>
> > Cc: stable@...r.kernel.org
> 
> I just tested with the 3 patches applied on 4.9-rc4 and could still
> reproduce the issue.

I've just tested the dev branch on both x86 and x86_64 and it doesn't reproduce for me;

root@...tests:~# mount -o ro,loop /tmp/OSS-2016-23-image  /mnt
mount: wrong fs type, bad option, bad superblock on /dev/loop0,
       missing codepage or helper program, or other error

       In some cases useful info is found in syslog - try
       dmesg | tail or so.
root@...tests:~# dmesg | tail -3
[  910.472554] EXT4-fs (loop0): Unrecognized mount option "" or missing value
[  910.479708] EXT4-fs (loop0): failed to parse options in superblock: 
[  910.486279] EXT4-fs (loop0): Invalid log block size: 4286906368
root@...tests:~# 

The critical patch should be:

    ext4: sanity check the block and cluster size at mount time

Can you double check your test?

Thanks,

						- Ted
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