Re: [fuse-devel] getdir can infinite loop with rm -rf

[Miklos S. <mi...@sz...>]

> I know that I should update my program and use the new *dir interfaces, 
> but there is a bug with the getdir, or the new mechanism if you use a 
> zero offset (not sure?).
> 
> Try this with a program that uses the old getdir interface:
> 
>     mkdir test ; touch test/one test/two test/three ; rm -rf test

Works for me.

What kind of 'rm' do you use?

$ rm --version
rm (coreutils) 5.2.1

> I think what is happening is that rm -rf will list the directory, remove 
> the contents, rewind the directory, list the directory, remove any 
> remaining (newly created) files, and loop like that until the directory 
> is empty.

This would be buggy as it is, because in some cases unlink() returning
success, doesn't necessarily mean, that the file was really deleted
(e.g. open file under NFS).

> Unfortunately, inside libfuse's do_readdir, if the directory file handle 
> buffer is already filled, it simply returns with the old contents of the 
> directory, and not the updated contents which result from the removal of 
> the contents of that directory.

Yes, it could be a bit more clever about caching the directory
contents.  However, that would present other problems: the posisions
obtained by telldir() would no longer be valid after a directory
modification.

> Of course, if you use the readdir implementation and accept offsets, 
> this problem does not occur.
> 
> The fix that I've attached will mark the buffer 'filled' to 0 when the 
> entire contents of the buffer have been read. This is of course still 
> only works if the entire directory is read, so we're still better off 
> using the new readdir interfaces.
> 
> The attached patch applies to 2.3.0, but it looks like the same problem 
> could occur in your current CVS view, but the patch would be slightly 
> different.

I'd rather not add this until we are sure where the problem lays.

Thanks,
Miklos