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Date: Wed, 1 Oct 2014 09:30:50 -0400
From: Rich Felker <>
Subject: Re: Re: A running list of questions from "porting" Slackware
 to musl

On Wed, Oct 01, 2014 at 09:48:17AM +0200, Szabolcs Nagy wrote:
> * Andy Lutomirski <> [2014-09-30 16:50:28 -0700]:
> > On 09/30/2014 08:50 AM, Rich Felker wrote:
> > > When gcc generates the canary-check code, on failure it normally
> > > calls/jumps to __stack_chk_fail. But for shared libraries, that call
> > > would go to a thunk in the library's PLT, which depends on the GOT
> > > register being initialized (actually this varies by arch; x86_64
> ....
> > 
> > On x86_64, this would be call * instead of call
> > whatever@....
> > 
> > (Even better: the loader could patch the PLT with a direct jump.  Could
> ....
> hm this seems to be a lot of complication just to crash
> if gcc had a -fcrash-on-ssp-chk-fail flag that simply generated
> a crash instruction that would be simpler/smaller/more secure
> (actually i think that should be the default behaviour)

Yes, it really should. Perhaps we could post a GCC bug report
requesting this with a link to one or more of the articles on
exploiting the introspective debug code in gcc/glibc crash handlers.


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