On Tue, Apr 02, 2024 at 07:40:33AM +0200, Andreas Schneider wrote:
> On Saturday, 30 March 2024 10:37:44 CEST Richard W.M. Jones wrote:
> > These are just my thoughts on a Saturday morning.  Feedback welcome of
> > course.
> 
> I find the use of the ifunc attribute is really uncommon at this place. I 
> would expect it in ffmpeg or some media codecs. In xz it looks like it is 
> only 
> there to hook in the payload. The software I know normally uses target 
> cloning.

In hindsight it's suspicious, but it's not generally suspicious for a
project that needs to generate optimal code for different
sub-architectures (eg. something that does fast decompression) to use
the mechanism for that purpose, ifunc.

That said, ifunc is a very complicated, fragile  but powerful mechanism
and I'd like to know from the glibc developers what we should
look out for.  For example:

 - Is it ever valid for ifunc to take control of functions in another
   library?  Can this be detected by ld.so?

 - Can some wrappers be developed to make it both easier and safer?

> I think the use of the ifunc attribute should be a red flag. Can't we check 
> for it with rpmlint and let the security team verify it?

Rich.

-- 
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