Re: [autofs] [RFC PATCH]autofs4: hang and proposed fix

[Christoph Hellwig <hch@infradead.org>]

On Tue, Dec 06, 2005 at 04:20:29PM -0500, Jeff Moyer wrote:
> hch> No, for current TOT that can't happen.  It could happen for older
> hch> kernels but nothing is doing it in the tree anymore and if anything
> hch> outside is doing it it's fundamentally broken.
> 
> This is a bit unclear to me.  What do you mean when you refer to "it" and
> "that" above?  Oh, and TOT is a TLA I haven't run across before.

TOT = top of tree.

To rephrease the above:  With current mainline the nameidata argument
is always valid when ->lookup or ->d_revalidate are called except when
the filesystem uses lookup_one_len.  lookup_one_len is a helper for fileystem
usage that is only valid to be used on the filesystems own trees.

> We know that there is at least one out of tree module that calls
> lookup_one_len, and ends up in the autofs4 revalidate code without the
> valid nameidata structure.  In this case, with your patch, wouldn't we
> blindly dereference the structure and cause an oops?  If so, who is at
> fault?

This out of tree module is wrong and always has been wrong.  Any actual
breakage of such a module is expected.

Do you happen to know what module that is?