linux-kernel - Re: [PATCH v5 05/11] vsprintf: Consolidate handling of unknown pointer specifiers

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Date:   Wed, 25 Apr 2018 16:08:26 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Petr Mladek <pmladek@...e.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        "Tobin C . Harding" <me@...in.cc>, Joe Perches <joe@...ches.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.cz>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 05/11] vsprintf: Consolidate handling of unknown
 pointer specifiers

On Wed, 2018-04-25 at 13:12 +0200, Petr Mladek wrote:
> There are few printk formats that make sense only with two or more
> specifiers. Also some specifiers make sense only when a kernel feature
> is enabled.
> 
> The handling of unknown specifiers is strange, inconsistent, and
> even leaking the address. For example, netdev_bits() prints the
> non-hashed pointer value or clock() prints "(null)".
> 
> Using WARN() looks like an overkill for this type of error. pr_warn()
> is not good either. It would by handled via printk_sage buffer and
> it might be hard to match it with the problematic string.
> 
> A reasonable compromise seems to be writing the unknown format
> specifier
> into the original string with a question mark, for example (%pC?).
> It should be self-explaining enough. Note that it is in brackets
> to follow the (null) style.

> +		return valid_string(buf, end, "(%pG?)", spec);

>  
>  	if (!IS_ENABLED(CONFIG_OF))
> -		return valid_string(buf, end, "(!OF)", spec);
> +		return valid_string(buf, end, "(%OF?)", spec);

"(%pOF?)" ?

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy