Messages in this thread | | | From | "" <> | Date | Tue, 12 May 2015 20:59:03 +0300 | Subject | Re: [PATCH] PM / clock_ops: Fix clock error check in __pm_clk_add() |
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On 05/12/2015 07:42 PM, Dmitry Torokhov wrote: > On Tue, May 12, 2015 at 04:55:39PM +0300, Grygorii.Strashko@linaro.org wrote: >> 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(). > > Jeez, that sequence was not meant to be taken literally, it does miss > error handling completely. If you notice the majority of users of this > API do something like below: > > i = 0; > while ((clk = of_clk_get(dev->of_node, i++)) && !IS_ERR(clk)) { > dev_dbg(dev, "adding clock '%s' to list of PM clocks\n", > __clk_get_name(clk)); > error = pm_clk_add_clk(dev, clk); > clk_put(clk); > if (error) { > dev_err(dev, "pm_clk_add_clk failed %d\n", error); > pm_clk_destroy(dev); > return error; > } > } > > i.e. it already validates clk pointer before passing it on since it > needs to know when to stop iterating.
np. It's just my opinion - if you agree that code will just crash in case of passing invalid @clk argument (in worst case:)
int __clk_get(struct clk *clk) { struct clk_core *core = !clk ? NULL : clk->core; ^^^ here
let it be.
-- regards, -grygorii
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