Messages in this thread | | | Subject | Re: [patch 00/13] vfs: add helpers to check r/o bind mounts | From | Miklos Szeredi <> | Date | Thu, 24 Apr 2008 18:16:53 +0200 |
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> > > > What is left is the guarantee, that the race-free r/o remounts will > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > > > always work and some obscure caller didn't forget to surround it with > ^^^^^^^^^^^^^^^^^ > > > Why are those so important? Yes, if we have multiple vfs_() calls, > > surround them with an extra want/drop pair. > > Which leaves you with the same need to audit all these suckers anyway.
Not really. Missing such calls would just make the *caller* buggy (i.e. racy with remount r/o), but it would not make the *filesystem* buggy. Big difference.
> I'm in principle fine with having such helper functions, *IF* they are > not sold as providing all protection one needs,
I'm not selling them as that.
> *IF* you are not expecting > to be able to fold all areas down into them and *IF* original ones are > left intact.
Left intact for whom, specifically? Another question you've managed to avoid answering.
> Modulo the like path_rename(), BTW - that one is just plain ugly API.
I'm all open to improvements.
> > > let alone removing the interface that doesn't require checks to be > > > vfsmount-based for all users. > > > > What users? There are paractically _no_ other users. The ones that > > there are (like reiserfs) should not be using them, and there are > > already some patches cleaning that mess up. > > OK, explain me, in small words, WTF should something that wants to do > operations on filesystem tree have a vfsmount. Slowly. And "r/o > bind loses value if it can be bypassed" is a hogwash - fs methods are > still there, so it *can* be bypassed just fine, thank you very much.
And we know what to do with such users.
> It's really up to caller. "But they won't be able to do open()" also > doesn't fly - again, it's up to whoever writes particular piece of code.
I understand your theory. But it has zero practical significance.
IOW it doesn't matter that someone _may_ want to access the filesystem without a vfsmount, if that someone doesn't exist.
Miklos
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