Re: CVS commit: src/sys/arch

[Anders Magnusson <ragge%ludd.ltu.se@localhost>]

Den 2016-11-25 kl. 13:04, skrev Maxime Villard:
> Le 24/11/2016 à 14:28, Masanobu SAITOH a écrit :
> > Hi!
> >
> > On 2016/11/19 18:22, Maxime Villard wrote:
> > > Module Name:    src
> > > Committed By:    maxv
> > > Date:        Sat Nov 19 09:22:04 UTC 2016
> > >
> > > Modified Files:
> > >     src/sys/arch/amd64/include: vmparam.h
> > >     src/sys/arch/i386/include: vmparam.h
> > >
> > > Log Message:
> > > Put a one-page redzone between userland and the PTE space on amd64 and
> > > i386.
> > >
> > > The PTE space is a critical region that maps the page tree, and bugs 
> > > have
> > > been found in both amd64 and i386 where the kernel would wrongly 
> > > overflow
> > > userland data on this area. This kind of bug is terrible, since it 
> > > allows
> > > userland to overwrite some entries of the page tree, which makes it 
> > > easy
> > > to patch the kernel text and get ring0 privileges.
> > >
> > >
> > > To generate a diff of this commit:
> > > cvs rdiff -u -r1.37 -r1.38 src/sys/arch/amd64/include/vmparam.h
> > > cvs rdiff -u -r1.82 -r1.83 src/sys/arch/i386/include/vmparam.h
> > >
> > > Please note that diffs are not public domain; they are subject to the
> > > copyright notices on the relevant files.
> >
> > My emacs dumps core with change.
> >
> > What should we do?
>
> ? It probably means there is some kind of stupid assumption or hack in
> emacs. If you could send me the core, the binary and tell me which 
> arch it
> is, that would be nice. AFAICT, emacs is known to be buggy on netbsd.
Some years ago (quite some years) I did a test by changing malloc() to 
only use mmap() and replacing sbrk() in libc with a large mmap() (if 
ever called).
Everything worked fine except emacs, which did some quite nasty things; 
IIRC it expected sbrk to get memory just above the data area or 
something similar.

So emacs has always been a big cause of trouble :-/

-- Ragge