Re: [uml-devel] problems compiling 2.6.17 against glibc 2.4

[Nix <nix@esperi.org.uk>]

On Sun, 25 Jun 2006, blaisorblade@yahoo.it announced authoritatively:
> On Wednesday 21 June 2006 21:38, Nix wrote:
[jmp_buf goes hidden]
>> This vile patch lets me compile but is almost certainly not good enough:
>> however, I don't know what *is* good enough: now that glibc is blocking
>> us from the layout of the jmp_buf, what's to stop them from changing it?
>> (Well, other than that it would break the ABI ;) )
> I made the same thought, but no, they have *already* changed it.
> Search for the message from Ulrich Drepper

It's not easy to find it given that little info :(

>                                            (and if you understand 
> the "security reasons" I'd be curious to hear them);

Well, there are obvious security problems with having pointers in
jmp_buf exposed: attackers who can exploit a buffer overflow and know
the location of a jmp_buf and its layout can force someone to longjmp()
to any location they like, regardless of -fstack-protector tricks. Even
FORTIFY_SOURCE won't protect against it if the buffer overrun didn't use
strcpy() or a similarly fortified call.

>                                                      also the below patch is 
> available in Jeff's tree from some time.

Aha, great minds kludge alike ;)

> I asked Jeff to #ifdef that code out for 2.6.17 release (since the below patch 
> was refused)... anyway Jeff found that we can take setjmp() implementation 
> from klibc and include it in UML.

Well, it wasn't ifdeffed out ;)

Using the uml setjmp() implementation seems like a good idea (or the uClibc one).

-- 
`NB: Anyone suggesting that we should say "Tibibytes" instead of
 Terabytes there will be hunted down and brutally slain.
 That is all.' --- Matthew Wilcox

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