Re: [Xen-devel] [PATCH 15/18] xenstore: New function xs_path_is_subpath

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Ian Campbell writes ("Re: [Xen-devel] [PATCH 15/18] xenstore: New function 
xs_path_is_subpath"):
> On Fri, 2011-12-09 at 18:54 +0000, Ian Jackson wrote:
> > +   if (childlen > parentlen && child[parentlen] != '/')
> > +           return false;
> 
> It took me a second to figure that this last statement was preventing
> false positives from sibling directories where one is a substring of the
> other. Worth a comment?

Probably, yes.

> Doesn't the correctness of this depend on whether parent has a trailing
> slash or not though?

We don't allow trailing slashes.  They don't work in xenstore
operations.  However, there is one exception: "/".  If parent is "/"
the algorithm is wrong.

So docs/misc/xenstore.txt needs updating to clarify the former and my
new function needs the latter fixing.

These are the perils of taking code that was correct in situ and
making a general function out of it, I guess ...

Ian.

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