Messages in this thread | | | From | "" <> | Date | Tue, 12 May 2015 16:55:39 +0300 | Subject | Re: [PATCH] PM / clock_ops: Fix clock error check in __pm_clk_add() |
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Hi Dmitry, On 05/09/2015 12:05 AM, Dmitry Torokhov wrote: > On Fri, May 08, 2015 at 10:59:04PM +0200, Geert Uytterhoeven wrote: >> On Fri, May 8, 2015 at 7:19 PM, Dmitry Torokhov >> <dmitry.torokhov@gmail.com> wrote: >>> 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 >> >> __clk_get() does the NULL check. > > No, not really. It _handles_ clk being NULL and returns "everything is > fine". In any case it is __clk_get's decision what to do. > > I dislike gratuitous checks of arguments passed in. Instead of relying > on APIs refusing grabage we better not pass garbage to these APIs in the > first place. So I'd change it to trust that we are given a usable > pointer and simply do: > > if (!__clk_get(clk)) { > kfree(ce); > return -ENOENTl > }
Not sure this is right thing to do, because this API initially was intended to be used as below [1]: clk = of_clk_get(dev->of_node, i)); ret = pm_clk_add_clk(dev, clk); clk_put(clk);
and of_clk_get may return ERR_PTR().
So, personally I prefer initial fix from Geert.
[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2014-October/296586.html
-- regards, -grygorii
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