Re: Re: [Security] /proc infoleaks

[Marcus Meissner <meissner () suse de>]

On Tue, Sep 07, 2010 at 01:13:45PM +0200, Sebastian Krahmer wrote:
> On Tue, Sep 07, 2010 at 03:51:03AM -0700, Andrew Morton wrote:
> > On Tue, 7 Sep 2010 10:35:46 +0200 Sebastian Krahmer <krahmer () suse de> wrote:
> >
> > > I have been elected to receive the bashing from all sides,
> > > so here we go.
> > > It is not about a new vulnerability or even a new discussion
> > > but needs to be discussed, at least that we have a clear
> > > statement about the status quo.
> > >
> > > Recent i-CAN-haz-MODHARDEN.c has shown once *again* that
> > > certain file permissions make no sense except to exploitation
> > > development. There is no reason to have files like
> > >
> > > /proc/kallsyms
> > > /proc/slabinfo
> > > /proc/zoneinfo
> > >
> > > and probably a lot of others world readable. The symbol
> > > addresses might be hard-coded for a certain targetlist
> > > inside the exploit so you can argue that there
> > > wont be any protection benefit from making it unreadable.
> > > However this argument aint a reason to also leak it for self-compiled
> > > kernels and doesnt even hold for dynamic/runtime content
> > > like slabinfos etc.
> > > It would be nice to have something like
> > >
> > > echo 1 > /proc/quiet
> > >
> > > or something like a umask for kernel-owned proc
> > > entries so that you have a polite default and are
> > > still able to enable it for certain profiling tools
> > > or whereever you need it.
> >
> > chmod 0440 /proc/slabinfo
> Heh, indeed. :-)
> Would it be a bad idea to have proc_create() use a more strict
> mode so it is non-leaking by default?

Yeah, sane and a bit more strict, defaults are missing.

The little pieces of information leakage out of the kernel should be fixed,
to raise the bar for kernel exploits in little steps at a time.

Ciao, Marcus