Re: [PATCH] zerocopy NFS updated

Mike Fedyk
2002-04-24T23:09:31Z

On Sat, Apr 13, 2002 at 02:34:12PM -0600, Eric W. Biederman wrote:
> Andi Kleen <ak@suse.de> writes:
>
> > On Sat, Apr 13, 2002 at 01:19:46PM -0600, Eric W. Biederman wrote:
> > > Could the garbage from ext3 in writeback mode be considered an
> > > information leak? I know that is why most places in the kernel
> > > initialize pages to 0. So you don't accidentally see what another
> > > user put there.
> >
> > Yes it could. But then ext2/ffs have the same problem and so far people were
> > able to live on with that.
>
> The reason I asked, is the description sounded specific to ext3. Also
> with ext3 a supported way to shutdown is to just pull the power on the
> machine. And the filesystem comes back to life without a full fsck.
>
> So if this can happen when all you need is to replay the journal, I
> have issues with it. If this happens in the case of damaged
> filesystem I don't.
>

Actually, with ext3 the only mode IIRC is data=journal that will keep this
from happening. In ordered or writeback mode there is a window where the
pages will be zeroed in memory, but not on disk.

Admittedly, the time window is largest in writeback mode, smaller in ordered
and smallest (non-existant?) in data journaling mode.

Mike