Re: [PATCH] clk_register_clkdev: remove format string interface

From: Russell King - ARM Linux
Date: Fri Sep 04 2015 - 04:59:34 EST

On Thu, Sep 03, 2015 at 01:54:07PM -0700, Kees Cook wrote:
> Many callers either use NULL or const strings for the third argument of
> clk_register_clkdev. For those that do not and use a non-const string,
> this is a risk for format strings being accidentally processed (for
> example in device names). As this interface is already used as if it
> weren't a format string (prints nothing when NULL), and there are zero
> users of the format strings, remove the format string interface to make
> sure format strings will not leak into the clkdev.
> $ git grep '\bclk_register_clkdev\b' | grep % | wc -l
> 0
> Unfortunately, all the internals expect a va_list even though they treat
> a NULL format string as special. To deal with this, we must pass either
> (..., "%s", string) or (..., NULL, NULL) so that a the va_list will be
> created correctly (passing the name as an argument, not a format string).

A more clearer way to write that would be:

if (dev_id)
cl = clkdev_create(hw, con_id, "%s", dev_id);
cl = clkdev_create(hw, con_id, NULL);

then it's obvious what's going on.

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