Linux-kernel mailing list archive 1999-37,: Re: nfsd Security: /// bad export. error

# Re: nfsd Security: /// bad export. error

Philippe Troin (phil@fifi.org)
13 Sep 1999 00:30:50 -0700

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"G. Allen Morris III" <gam3@ixlabs.com> writes:

> My guess of what is happing here is that there the original
> dentry is flushed out of memory. Then when the file is next
> accessed the path has to be rebuilt. This generate all new
> dentries, so the search to find the export point fails.
>
> The solution might be:
>
> --- nfsfh.c.orig Sun Sep 12 23:15:35 1999
> +++ nfsfh.c Sun Sep 12 23:16:26 1999
> @@ -1124,7 +1124,7 @@
>
> do {
> tdentry = tdentry->d_parent;
> - if (exp->ex_dentry == tdentry)
> + if (exp->ex_dentry->d_inode->i_ino == tdentry->d_inode->i_ino)
> break;
> /* executable only by root and we can't be root */
> if (current->fsuid &&
>
>
> Or something a long those lines. (I am guessing.)

Well, we should probably also check the device... And a lot of code
checks also for the directory inode in case of a file (any clue why we
need to check dev/ino/dirino ? I thought that dev/ino ought to be
sufficient...)

Mmmh, I think there's something more subtle going on.
The problem lasts a few seconds where all fh lookups fail, and after
that everything is back to normal... If the original dentry were
flushed out, the problem would persist.

Plus, I think the export structure keeps the dentry locked.

But, I'm not a dcache guru anyways...

Phil.

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