Re: PATCH - ext2fs privacy (i.e. secure deletion) patch

Valdis.Kletnieks
2004-02-05T04:38:41Z

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On Wed, 04 Feb 2004 18:47:54 EST, Bill Davidsen said:
> > This of course implies that 'chattr +s' (or whatever it was) has to fail
> > if the link count isn't exactly one.
>
> Do you disagree that the count does need to be one?

I'm not prepared to say that there's no scenario where we *dont* care
how many links there are, as long as the file *does* get wiped when the
last one goes away.

The MH mail handler stores each message in a file - so a mail message is easily
stored in multiple folders by simply using multiple hard links. I could
easily see having mail that I want to +s and go away when I remove it from
the last folder it was in....

> I agree with everything you said, "useful" doesn't always map to "easy."
> But if you agree that the count needs to be one on files, then you could
> also fail if you tried to add it to a directory which was not empty.

Yes you could. The question is whether that's a desired semantic or not.

> In case I didn't make it clear, the use I was considering was to create
> a single directory in which created files would really go away when
> deleted. I hadn't considered doing it after files were present, what you
> say about overhead is clearly an issue. I think I could even envision
> some bizarre race conditions if the kernel had to do marking of each
> file, so perhaps it's impractical.

As I said, ugly and murky....

> But what happens when the 'setgid' bit is put on a directory? At least
> in 2.4 existing files do NOT get the group set, only files newly
> created. So unless someone feels that's a bug which needs immediate
> fixing, I can point to it as a model by which the feature could be
> practically implemented.

Ahh.. but now you're suggesting a different model than "directory must
be empty". Obviously more discussion of what we *want* it to do is needed ;)

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