Re: ath10k: ret used but uninitialized

From: Geert Uytterhoeven
Date: Fri Jul 07 2017 - 10:16:11 EST

Hi Arnd,

On Fri, Jul 7, 2017 at 4:14 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote:
> On Fri, Jul 7, 2017 at 12:04 PM, Kalle Valo <kvalo@xxxxxxxxxxxxxxxx> wrote:
>> Erik Stromdahl <erik.stromdahl@xxxxxxxxx> writes:
>>>> With gcc 4.1.2:
>>>> drivers/net/wireless/ath/ath10k/sdio.c: In function
>>>> âath10k_sdio_mbox_rxmsg_pending_handlerâ:
>>>> drivers/net/wireless/ath/ath10k/sdio.c:676: warning: âretâ may be used
>>>> uninitialized in this function
>>>>> +
>>>>> + *done = true;
>>>>> +
>>>>> + /* Copy the lookahead obtained from the HTC register table into our
>>>>> + * temp array as a start value.
>>>>> + */
>>>>> + lookaheads[0] = msg_lookahead;
>>>>> +
>>>>> + timeout = jiffies + SDIO_MBOX_PROCESSING_TIMEOUT_HZ;
>>>> Although very unlikely due to the long timeout, if the code is preempted here,
>>>> and the loop below never entered, ret will indeed be uninitialized.
>>>> It's unclear to me what the proper initialization would be, though, so
>>>> that's why I didn't send a patch.
>>> I think it would be best to use 0 as initial value of ret in this case.
>>> This will make all other interrupts be processed in a normal way.
>>> Kalle: Should I create a new patch (initializing ret with zero)?
>> Yes, please send a new patch fixing this.
>> But I don't like that much with the style of initialising ret to zero,
>> it tends to hide things. Instead my preference is something like below
>> where the error handling is more explicit and easier to find where it's
>> exactly failing. But that's just an example how I would try to solve it,
>> it still lacks the handling of -ECANCEL etc.
> I think I would simply replace the "while() {}" loop with "do{} while()",
> as that would guarantee it to be run at least once in a way that the
> compiler can see.

Right, that's probably the simplest and cleanest solution.



Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds