[PATCH] UBUNTU: [Config] ext3 defaults to ordered mode

[Ben Hutchings]

On Wed, 2010-01-27 at 08:53 +0100, Martin Pitt wrote:
> Hello all,
> 
> Tim Gardner [2010-01-21  7:00 -0700]:
> > SRU policy states that patches must fix a real problem. IMHO this does
> > not fix the root issue, which is the crash, _not_ the file system
> > corruption. No file system code will be able to withstand crashes at the
> > right critical point.
> 
> I have read the bug report now, and TBH I fail to see the security
> problem here. If due to a crash I can still read old data from a file,
> that just means that my recent attempt to remove/overwrite the data
> from a file failed. Well, if the computer had crashed ten microseconds
> earlier, and thus the disk wouldn't have managed to write the metadata
> either, I would have the very same problem. Or did I misunderstood the
> problem here?
[...]

With the data=writeback setting, it is possible for block allocation to
be committed to disk before the block contents.  This means that a file
which was extended just before a crash may contain data from a
previously deleted file after journal replay, and that can be a security
problem.  See <http://lwn.net/Articles/328363/>.

(The proposed data=guarded setting would fix this problem without the
full overhead of data=ordered, but it has not been accepted yet.)

Ben.

-- 
Ben Hutchings
The obvious mathematical breakthrough [to break modern encryption] would be
development of an easy way to factor large prime numbers. - Bill Gates
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