Re: [PATCH] PM / clock_ops: Fix clock error check in __pm_clk_add()

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Fri, May 08, 2015 at 10:47:43AM +0200, Geert Uytterhoeven wrote:
> In the final iteration of commit 245bd6f6af8a62a2 ("PM / clock_ops: Add
> pm_clk_add_clk()"), a refcount increment was added by Grygorii Strashko.
> However, the accompanying IS_ERR() check operates on the wrong clock
> pointer, which is always zero at this point, i.e. not an error.
> This may lead to a NULL pointer dereference later, when __clk_get()
> tries to dereference an error pointer.
> 
> Check the passed clock pointer instead to fix this.

Frankly I would remove the check altogether. Why do we only check for
IS_ERR and not NULL or otherwise validate the pointer? The clk is passed
in and we do not call any API that would return ERR_PTR-encoded value to
us so we shoud lnot even try to handle IS_ERR here.

> 
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> Fixes: 245bd6f6af8a62a2 ("PM / clock_ops: Add pm_clk_add_clk()")
> ---
> Note that there are no users of pm_clk_add_clk() in next-20150508, so
> for now no in-tree code is affected.
> ---
>  drivers/base/power/clock_ops.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/base/power/clock_ops.c b/drivers/base/power/clock_ops.c
> index 7fdd0172605afe1b..c7b0fcebf168cabe 100644
> --- a/drivers/base/power/clock_ops.c
> +++ b/drivers/base/power/clock_ops.c
> @@ -93,7 +93,7 @@ static int __pm_clk_add(struct device *dev, const char *con_id,
>  			return -ENOMEM;
>  		}
>  	} else {
> -		if (IS_ERR(ce->clk) || !__clk_get(clk)) {
> +		if (IS_ERR(clk) || !__clk_get(clk)) {
>  			kfree(ce);
>  			return -ENOENT;
>  		}
> -- 
> 1.9.1
> 

Thanks.

-- 
Dmitry