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Re: Preview: portable dumper


From: Paul Eggert
Subject: Re: Preview: portable dumper
Date: Sat, 3 Dec 2016 13:54:20 -0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1

Richard Stallman wrote:
What Emacs does with the contents of an incoming packet is mainly
to turn it into Lisp objects and make that available at Lisp level.
That means not much opportunity for such a bug to occur.

Sure, but incoming packets are not random and attackers can design packets to exploit Emacs bugs. So any opportunity whatsoever in Lisp conversion is more of concern than it would be for more-typical pointer bugs. And as Daniel mentioned, attackers will likely focus on the occasions when Emacs converts packet contents to non-Lisp objects.

I have been looking into improving checking in this area, by using the -fcheck-pointer-bounds option introduced in GCC 5 and supported by some newer CPUs. Although -fcheck-pointer-bounds should help, it won't be perfect and it will be disabled by default due to its performance cost.



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