On 8/14/25 1:25 PM, Krzysztof Kozlowski wrote:
> On 14/08/2025 11:15, Konrad Dybcio wrote:
>> On 8/14/25 8:32 AM, Krzysztof Kozlowski wrote:
>>> The ISR calls dev_pm_opp_find_bw_ceil(), which can return EINVAL, ERANGE
>>> or ENODEV, and if that one fails with ERANGE, then it tries again with
>>> floor dev_pm_opp_find_bw_floor().
>>>
>>> Code misses error checks for two cases:
>>> 1. First dev_pm_opp_find_bw_ceil() failed with error different than
>>> ERANGE,
>>> 2. Any error from second dev_pm_opp_find_bw_floor().
>>>
>>> In an unlikely case these error happened, the code would further
>>> dereference the ERR pointer. Close that possibility and make the code
>>> more obvious that all errors are correctly handled.
>>>
>>> Reported by Smatch:
>>> icc-bwmon.c:693 bwmon_intr_thread() error: 'target_opp' dereferencing possible ERR_PTR()
>>>
>>> Fixes: b9c2ae6cac40 ("soc: qcom: icc-bwmon: Add bandwidth monitoring driver")
>>> Cc: <stable@xxxxxxxxxxxxxxx>
>>> Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
>>> Closes: https://lore.kernel.org/r/aJTNEQsRFjrFknG9@stanley.mountain/
>>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
>>>
>>> ---
>>>
>>> Some unreleased smatch, though, because I cannot reproduce the warning,
>>> but I imagine Dan keeps the tastiests reports for later. :)
>>> ---
>>> drivers/soc/qcom/icc-bwmon.c | 3 +++
>>> 1 file changed, 3 insertions(+)
>>>
>>> diff --git a/drivers/soc/qcom/icc-bwmon.c b/drivers/soc/qcom/icc-bwmon.c
>>> index 3dfa448bf8cf..597f9025e422 100644
>>> --- a/drivers/soc/qcom/icc-bwmon.c
>>> +++ b/drivers/soc/qcom/icc-bwmon.c
>>> @@ -656,6 +656,9 @@ static irqreturn_t bwmon_intr_thread(int irq, void *dev_id)
>>> if (IS_ERR(target_opp) && PTR_ERR(target_opp) == -ERANGE)
>>> target_opp = dev_pm_opp_find_bw_floor(bwmon->dev, &bw_kbps, 0);
>>>
>>> + if (IS_ERR(target_opp))
>>> + return IRQ_HANDLED;
>>
>> So the thunk above checks for a ceil freq relative to bw_kbps and then
>> if it doesn't exist, for a floor one
>>
>> Meaning essentially if we fall into this branch, there's no OPPs in the
>> table, which would have been caught in probe
> Yes, unless:
> 1. There is a bug in the opp code
> 2. Probe code is anyhow changed in the future
>
> I think the code should be readable and obviouswithin the function, not
> depend on some pre-checks in the probe. But if you think that's
> defensive coding I can also add a comment to silence future Smatch
> complains.
I ultimately don't *really* mind either, just wanted to point out that
currently it's effectively a false positive
Konrad
