From mboxrd@z Thu Jan  1 00:00:00 1970
Date: Wed, 4 Oct 2017 10:56:57 +0200
From: Greg KH <gregkh@linuxfoundation.org>
Message-ID: <20171004085657.GC28247@kroah.com>
References: <1506816410-10230-1-git-send-email-me@tobin.cc>
 <1506816410-10230-3-git-send-email-me@tobin.cc>
 <20171002104205.GC3823@arm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20171002104205.GC3823@arm.com>
Subject: Re: [kernel-hardening] [RFC V2 2/6] lib: vsprintf: whitelist stack
 traces
To: Will Deacon <will.deacon@arm.com>
Cc: "Tobin C. Harding" <me@tobin.cc>, Petr Mladek <pmladek@suse.com>, Joe Perches <joe@perches.com>, Ian Campbell <ijc@hellion.org.uk>, Sergey Senozhatsky <sergey.senozhatsky@gmail.com>, kernel-hardening@lists.openwall.com, linux-kernel@vger.kernel.org, Catalin Marinas <catalin.marinas@arm.com>, Steven Rostedt <rostedt@goodmis.org>, William Roberts <william.c.roberts@intel.com>, Chris Fries <cfries@google.com>, Dave Weinstein <olorin@google.com>
List-ID: <kernel-hardening.lists.openwall.com>

On Mon, Oct 02, 2017 at 11:42:05AM +0100, Will Deacon wrote:
> On Sun, Oct 01, 2017 at 11:06:46AM +1100, Tobin C. Harding wrote:
> > Use the %pP functionality to explicitly allow kernel
> > pointers to be logged for stack traces.
> > 
> > Signed-off-by: Tobin C. Harding <me@tobin.cc>
> > ---
> >  arch/arm64/kernel/traps.c | 4 ++--
> >  kernel/printk/printk.c    | 2 +-
> >  2 files changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
> > index 5ea4b85..fe09660 100644
> > --- a/arch/arm64/kernel/traps.c
> > +++ b/arch/arm64/kernel/traps.c
> > @@ -147,7 +147,7 @@ void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
> >  	struct stackframe frame;
> >  	int skip;
> >  
> > -	pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
> > +	pr_debug("%s(regs = %pP tsk = %pP)\n", __func__, regs, tsk);
> 
> Why do we care for pr_debug?

Because you really want the real value?  Seems to make sense to me...

thanks,

greg k-h