Re: "Local variables" denial-of-service attack

[Ulrich Mueller]

>>>>> On Fri, 09 Jan 2009, Stefan Monnier wrote:

>> Local Variab*les:
>> byte-compile-warnings: #1=("circular" "object" . #1#)
>> End:

> Hmm... that's not good.  It's not the end of the world since it's "only"
> a DoS, but we should try and fix it.  I see two ways:
> 1 - don't allow (in file-local vars and .dir-local.el) the # escapes
>     that permit creation of those circular objects.
> 2 - be more careful about circularities in the
>     safe-local-variable predicates.

> Nb 1 is easier and will solve it "for all cases", so it's probably
> a better choice.

But for 1 you would have to communicate to "read1" that it's reading
local variables? It's not obvious to me how one would do this in a
clean way. (I'm not very familiar with that code though).

Whereas for 2, adding a simple check like (nthcdr (safe-length foo) foo)
being nil should be sufficient in most (all?) cases.

Ulrich