From: Joe Perches <joe@perches.com>
To: Kees Cook <kees.cook@canonical.com>
Cc: linux-kernel@vger.kernel.org,
Rusty Russell <rusty@rustcorp.com.au>, Tejun Heo <tj@kernel.org>,
Marcus Meissner <meissner@suse.de>,
Jason Wessel <jason.wessel@windriver.com>,
Eugene Teo <eugeneteo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Bjorn Helgaas <bjorn.helgaas@hp.com>,
Len Brown <len.brown@intel.com>, Changli Gao <xiaosuo@gmail.com>,
Dan Rosenberg <drosenberg@vsecurity.com>
Subject: Re: RFC: introduce "K" flag for printf, similar to %pK
Date: Tue, 25 Jan 2011 09:41:13 -0800 [thread overview]
Message-ID: <1295977273.4316.3.camel@Joe-Laptop> (raw)
In-Reply-To: <20110125172841.GY4979@outflux.net>
On Tue, 2011-01-25 at 09:28 -0800, Kees Cook wrote:
> On Mon, Jan 24, 2011 at 06:17:04PM -0800, Joe Perches wrote:
> > On Mon, 2011-01-24 at 18:03 -0800, Kees Cook wrote:
> > > In the interests of hiding kernel addresses from userspace (without
> > > messing with file permissions), I want to use %pK for /proc/kallsyms and
> > > /proc/modules, but this results in changing several %x's to %p's. The
> > > primary side-effects is that some legitimately "0" value things in
> > > /proc/kallsyms turn into "(null)".
> >
> > Another option would be to allow '0' for
> > kernel pointers.
>
> But then this changes the behavior of %p where (null) is expected. (i.e.
> when switching from %p to %pK.)
If you really want no change to any existing cases,
change it to "%pk" and a new case label.
> I'm personally fine with that, as I suspect anything parsing the output
> that can handle finding "(null)" will be fine with "0" too. But the other
> way around, not so much. :)
Maybe there's a case where somebody changed a kernel pointer
from %p to %pK that demands "(null)", but I can't think of one.
cheers, Joe
prev parent reply other threads:[~2011-01-25 17:41 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-25 2:03 RFC: introduce "K" flag for printf, similar to %pK Kees Cook
2011-01-25 2:04 ` [PATCH 1/2] use %pK for /proc/kallsyms and /proc/modules Kees Cook
2011-01-25 2:07 ` [PATCH 2/2] use %pK and %Klx " Kees Cook
2011-01-25 2:17 ` RFC: introduce "K" flag for printf, similar to %pK Joe Perches
2011-01-25 17:28 ` Kees Cook
2011-01-25 17:41 ` Joe Perches [this message]
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