linux-kernel - Re: [PATCH] lockdep: Make print

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Date:   Mon, 16 Sep 2019 20:07:55 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Paul E. McKenney" <paulmck@...ux.ibm.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lockdep: Make print_lock() address visible

On Mon, Sep 16, 2019 at 06:39:46PM -0700, keescook@...omium.org wrote:
> commit 519248f36d6f3c80e176f6fa844c10d94f1f5990
> Author: Paul E. McKenney <paulmck@...ux.ibm.com>
> Date:   Thu May 30 05:39:25 2019 -0700
> 
>     lockdep: Make print_lock() address visible
>     
>     Security is a wonderful thing, but so is the ability to debug based on
>     lockdep warnings.  This commit therefore makes lockdep lock addresses
>     visible in the clear.
>     
>     Signed-off-by: Paul E. McKenney <paulmck@...ux.ibm.com>
> 
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index 4861cf8e274b..4aca3f4379d2 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -620,7 +620,7 @@ static void print_lock(struct held_lock *hlock)
>  		return;
>  	}
>  
> -	printk(KERN_CONT "%p", hlock->instance);
> +	printk(KERN_CONT "%px", hlock->instance);
>  	print_lock_name(lock);
>  	printk(KERN_CONT ", at: %pS\n", (void *)hlock->acquire_ip);
>  }

Just to clarify: this is only visible under CONFIG_LOCKDEP, yes? That's
not a state anyone would run a production system under, I'd hope.

-- 
Kees Cook