Messages in this thread | | | Date | Thu, 3 Nov 2005 10:11:07 +1100 | From | Nathan Scott <> | Subject | Re: XFS information leak during crash |
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Hello Jan,
On Wed, Nov 02, 2005 at 10:27:22PM +0100, Jan Kasprzak wrote: > Hello, world!\n > > I have found that after the system crash (e.h. a hard reset or a power > failure) XFS corrupts files which have been written to just before the crash: > The result is that those files contain data from random blocks on the > disk (e.g. from previously deleted files). This can have security/privacy > implications - users can see the contents of other users' old files.
If you think you have found a security issue, it would be courteous to at least discuss this with the maintainers first. And since you are a frequent linux-xfs list poster too, it seems a bit odd that you're reporting this on linux-kernel instead... *shrug*, whatever.
This issue affects every filesystem, right? Or are you claiming its only XFS affected here? Have you run your parallel-buffered-writers test case on any other filesystems? I'd be interested in the results, in particular, with all of the data=xxx modes of other filesystems.
> either). Does XFS support a something like ext3's "data=ordered" mount > option?
No, it doesn't.
> Otherwise it is pretty unusable on multi-user systems.
That's a ridiculous assertion. While this small metadata vs. buffered- data-write window exists on _any_ filesystem not using a data=ordered/ data=journaled mode (which I believe is quite a common mode of operation even on filesystems that offer those modes), it is impossible to exploit this in any sane way. You'd think people on a multi-user system might actually notice the machine being frequently rebooted while you try to tickle this window to get at "interesting" uninitialised freespace, no?
Having said that, a data=ordered mode for XFS would be a nice feature. It just hasn't reached the top of our priority list, and its not been offered up as a patch by anyone yet. If anyone's interested in writing this, they should coordinate with hch and myself - there's a fair bit of I/O path work being done at the moment, which in the end will make a data=ordered mode alot easier to implement.
cheers.
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