linux-kernel - Re: [PATCH] tracing/user_events: Don't use %pK through printk

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Message-ID: <20250219081236-812a157c-5c60-41af-a7c8-f75f9da5e92a@linutronix.de>
Date: Wed, 19 Feb 2025 08:14:34 +0100
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Steven Rostedt <rostedt@...dmis.org>, 
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH] tracing/user_events: Don't use %pK through printk

On Wed, Feb 19, 2025 at 09:10:23AM +0900, Masami Hiramatsu wrote:
> On Mon, 17 Feb 2025 14:16:12 +0100
> Thomas Weißschuh <thomas.weissschuh@...utronix.de> 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.
> > 
> > Link: https://lore.kernel.org/lkml/20250113171731-dc10e3c1-da64-4af0-b767-7c7070468023@linutronix.de/
> 
> This is only for the kernel pointer, but the "uaddr" below means it
> has a user space address. So I think this does not need to be applied.

"uaddr" is formatted with %llx, which is fine.
"%pK" is used for mm->mm, which is a kernel pointer.

> Thank you,
> 
> > Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
> > ---
> >  kernel/trace/trace_events_user.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
> > index 97325fbd62836f4fb477c4a2b2936eff544291ec..3effc6fce20e65a8077de5221eb69db04fb1a775 100644
> > --- a/kernel/trace/trace_events_user.c
> > +++ b/kernel/trace/trace_events_user.c
> > @@ -455,7 +455,7 @@ static void user_event_enabler_fault_fixup(struct work_struct *work)
> >  	if (ret && ret != -ENOENT) {
> >  		struct user_event *user = enabler->event;
> >  
> > -		pr_warn("user_events: Fault for mm: 0x%pK @ 0x%llx event: %s\n",
> > +		pr_warn("user_events: Fault for mm: 0x%p @ 0x%llx event: %s\n",
> >  			mm->mm, (unsigned long long)uaddr, EVENT_NAME(user));
> >  	}
> >  
> > 
> > ---
> > base-commit: 0ad2507d5d93f39619fc42372c347d6006b64319
> > change-id: 20250217-restricted-pointers-trace-a0fb12707ac6
> > 
> > Best regards,
> > -- 
> > Thomas Weißschuh <thomas.weissschuh@...utronix.de>