From: Dan Rosenberg <drosenberg@vsecurity.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org,
linux-security-module@vger.kernel.org, netdev@vger.kernel.org,
jmorris@namei.org, eugeneteo@kernel.org, kees.cook@canonical.com,
mingo@elte.hu, davem@davemloft.net
Subject: Re: [PATCH v2] kptr_restrict for hiding kernel pointers from unprivileged users
Date: Sat, 18 Dec 2010 00:22:44 -0500 [thread overview]
Message-ID: <1292649765.10804.42.camel@dan> (raw)
In-Reply-To: <20101217172231.8842f5cc.akpm@linux-foundation.org>
On Fri, 2010-12-17 at 17:22 -0800, Andrew Morton wrote:
> On Fri, 17 Dec 2010 20:12:39 -0500
> Dan Rosenberg <drosenberg@vsecurity.com> wrote:
>
> > >
> > > So what's next? We need to convert 1,000,000 %p callsites to use %pK?
> > > That'll be fun. Please consider adding a new checkpatch rule which
> > > detects %p and asks people whether they should have used %pK.
> >
> > The goal of this format specifier is specifically for pointers that are
> > exposed to unprivileged users. I agree that hiding all kernel pointers
> > would be nice, but I don't expect the angry masses to ever agree to
> > that. For now, I'll isolate specific cases, especially in /proc, that
> > are clear risks in terms of information leakage. I'll also be skipping
> > over pointers written to the syslog, since I think hiding that
> > information is dmesg_restrict's job.
>
> Well... some administrators may wish to hide the pointer values even
> for privileged callers. That's a pretty trivial add-on for the code
> which you have, and means that those admins can also suppress the
> pointers for IRQ-time callers. More /proc knobs :)
>
I can add a "2" setting that hides %pK pointers regardless of privilege
level, which I agree is a useful option. But because it would be built
into the same format specifier, you still couldn't use %pK in interrupt
context (in case the sysctl wasn't set to 2).
> Then again, perhaps those admins would be OK if we simply disabled
> plain old %p everywhere. In which case we're looking at a separate
> patch, I suggest.
I would be happy to do this from a security perspective, but I'd imagine
there's a pretty high risk of things breaking by doing such a sweeping
change.
-Dan
next prev parent reply other threads:[~2010-12-18 5:22 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-11 0:05 [PATCH v2] kptr_restrict for hiding kernel pointers from unprivileged users Dan Rosenberg
2010-12-11 0:11 ` Kees Cook
2010-12-18 0:44 ` Andrew Morton
2010-12-18 1:12 ` Dan Rosenberg
2010-12-18 1:22 ` Andrew Morton
2010-12-18 5:22 ` Dan Rosenberg [this message]
2010-12-18 0:53 ` Andrew Morton
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