Re: [regression] Re: brk randomization breaks columns

[Ingo Molnar <mingo@elte.hu>]

* Pavel Machek <pavel@ucw.cz> wrote:

> > > > I am still not completely sure. It might be a regression, but it 
> > > > also might just trigger the bug in ancient version in libc.so.5 
> > > > which might be fixed in some later version [...]
> > > 
> > > which too is a regression ...
> > > 
> > > really, lets add a sysctl for this, and a .config option that 
> > > either disables or enables it. Then we will default to disabled. 
> > > (but users can enable it - and distros can build their kernels 
> > > with this .config option enabled)
> > 
> > I don't think kernel should care about programs which are buggy and 
> > make invalid assumptions, and that's the case here.  I remember we 
> > have been
> 
> Those "invalid assumptions" crept into documentation. Everybody knew 
> heap starts at the end of bss in 1995.

what matters most isnt really any documentation but what programs really 
do, and how it affects users.

in this case i think we should offer a .config option to set the 
randomization behavior, and should perhaps make the more conservative 
one the default.

New distros (with 10,000+ binaries that work just fine with 
randomization) will turn on max randomization by default, while people 
like you who mix 1996 binaries with a 2008 kernel will use a more 
conservative default.

	Ingo