linux-kernel - Re: [PATCH] ARM: mm: Don't use %pK through printk

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Message-ID: <20250218113329-baca2d3d-5b2f-4f0a-8953-75fbba9bce71@linutronix.de>
Date: Tue, 18 Feb 2025 11:41:13 +0100
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: mm: Don't use %pK through printk

On Tue, Feb 18, 2025 at 10:27:49AM +0000, Russell King (Oracle) wrote:
> On Mon, Feb 17, 2025 at 08:38:37AM +0100, Thomas Weißschuh wrote:
> > Restricted pointers ("%pK") are not meant to be used through printk().
> > It can unintentionally expose security sensitive, raw pointer values.
> > 
> > Use regular pointer formatting instead.
> 
> ... which means that the warning is pointless because no one can debug
> it when someone reports that this has fired.

For the most common setups which using the default kptr_restrict=0,
%pK is already the same as %p.

> While I get the security issue, changing this is severely harmful to
> fixing problems should this warning fire.

My next goal is to get rid of the easy to misuse %pK.
If the address is really always important then %px can be used.


Thomas