[bug report] soundwire: qcom: Check device status before reading devid

[Srinivas Kandagatla]

On 08/07/2022 09:45, Dan Carpenter wrote:
> On Fri, Jul 08, 2022 at 09:31:31AM +0100, Srinivas Kandagatla wrote:
>> Hi Dan,
>>
>> On 08/07/2022 09:08, Dan Carpenter wrote:
>>> Hello Srinivas Kandagatla,
>>>
>>> The patch aa1262ca6695: "soundwire: qcom: Check device status before
>>> reading devid" from Jul 6, 2022, leads to the following Smatch static
>>> checker warning:
>>>
>>> 	drivers/soundwire/qcom.c:484 qcom_swrm_enumerate()
>>> 	error: buffer overflow 'ctrl->status' 11 <= 11
>>>
>>> drivers/soundwire/qcom.c
>>>       471 static int qcom_swrm_enumerate(struct sdw_bus *bus)
>>>       472 {
>>>       473         struct qcom_swrm_ctrl *ctrl = to_qcom_sdw(bus);
>>>       474         struct sdw_slave *slave, *_s;
>>>       475         struct sdw_slave_id id;
>>>       476         u32 val1, val2;
>>>       477         bool found;
>>>       478         u64 addr;
>>>       479         int i;
>>>       480         char *buf1 = (char *)&val1, *buf2 = (char *)&val2;
>>>       481
>>>       482         for (i = 1; i <= SDW_MAX_DEVICES; i++) {
>>>                        ^^^^^
>>> This a loop that starts from 1 instead of 0.  I looked at the
>>> surrounding context and it seems like it should be a normal loop that
>>> starts at 0 and goes to < SDW_MAX_DEVICES.
>>>
>>
>> In SoundWire world device id 0 is special one and used for enumerating the
>> SoundWire devices.
>>
>> Only addresses from 1-11 are valid devids that can be assigned to devices by
>> the host/controller.
>>
>> This part of the code is reading the devids assigned by the hw
>> auto-enumeration, So the loop start from 1 is correct here.
>>
>>
>>> (Or possibly the other loops are buggy as well).
>>
>> Atleast this code is fine, but I see other places where are starting from 0
>> which could be fixed but the SoundWire core will ignore the status for devid
>> 0.
> 
> This code is *not* fine either because it should be < instead of <=.
> 
> It might be that we always hit a zero first and break so the bug might
> not affect users but it's still wrong.

I agree, Let me send a fix or send a v2.

--srini
> 
> regards,
> dan carpenter
>