linux-kernel - Re: [PATCH v3] vsprintf: Check real user/group id for %pK

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Date:	Wed, 09 Oct 2013 15:14:21 -0700
From:	Joe Perches <joe@...ches.com>
To:	Ryan Mallon <rmallon@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, eldad@...refinery.com,
	Jiri Kosina <jkosina@...e.cz>, jgunthorpe@...idianresearch.com,
	Dan Rosenberg <dan.j.rosenberg@...il.com>,
	Kees Cook <keescook@...omium.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	George Spelvin <linux@...izon.com>,
	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] vsprintf: Check real user/group id for %pK

On Thu, 2013-10-10 at 09:04 +1100, Ryan Mallon wrote:
> On 10/10/13 09:00, Joe Perches wrote:
[]
> > Move the interrupt tests and pK-error printk
> > into case 1:
> > 
> > It's the only case where CAP_SYSLOG needs to be
> > tested so it doesn't need to be above the switch.
> 
> Like I said, I think it is useful to do the pK-error check anyway. It is
> checking for internal kernel bugs, since if 'pK-error' ever gets
> printed, then some kernel code is doing the wrong thing.

I think you don't quite understand how kptr_restrict works.

If it's 0, then the ptr value is always emitted naturally.
if it's 2, then the ptr value is always emitted as 0.

> Therefore, I
> think it is useful to print it always (I would argue it even makes sense
> when kptr_restrict=0).

How?  Maybe it's me that doesn't quite understand.


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