Re: [PATCH] Fix mmap_kmem (was: [question] What's the difference between /dev/kmem and /dev/mem)

Joshua Hudson
2005-08-13T16:57:09Z

On 8/13/05, Arjan van de Ven <arjan@infradead.org> wrote:
> On Fri, 2005-08-12 at 09:35 -0700, Linus Torvalds wrote:
> >
> > On Thu, 11 Aug 2005, Steven Rostedt wrote:
> > >
> > > Found the problem. It is a bug with mmap_kmem. The order of checks is
> > > wrong, so here's the patch. Attached is a little program that reads the
> > > System map looking for the variable modprobe_path. If it finds it, then
> > > it opens /dev/kmem for read only and mmaping it to read the contents of
> > > modprobe_path.
> >
> > I'm actually more inclined to try to deprecate /dev/kmem.. I don't think
> > anybody has ever really used it except for some rootkits. It only exists
> > in the first place because it's historical.
> >
> > We do need to support /dev/mem for X, but even that might go away some
> > day.
> >
> > So I'd be perfectly happy to fix this, but I'd be even happier if we made
> > the whole kmem thing a config variable (maybe even default it to "off").
>
I believe rootkit detectors, as well as some versions of ps (wchan
field) use kmem.