linux-kernel - Re: Build regressions/improvements in v6.4 (wireless/airo)

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Date:   Sun, 9 Jul 2023 06:12:22 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     linux-kernel@...r.kernel.org, Kalle Valo <kvalo@...nel.org>,
        linux-wireless@...r.kernel.org,
        John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
Subject: Re: Build regressions/improvements in v6.4 (wireless/airo)



On 7/9/23 01:27, Geert Uytterhoeven wrote:
> Hi Randy,
> 
> On Sun, Jul 9, 2023 at 4:46 AM Randy Dunlap <rdunlap@...radead.org> wrote:
>> On 6/26/23 01:24, Geert Uytterhoeven wrote:
>>> On Mon, 26 Jun 2023, Geert Uytterhoeven wrote:
>>>> JFYI, when comparing v6.4[1] to v6.4-rc7[3], the summaries are:
>>>>  - build errors: +1/-0
>>>
>>>   + /kisskb/src/drivers/net/wireless/cisco/airo.c: error: 'status_rid.currentXmitRate' is used uninitialized [-Werror=uninitialized]:  => 6163:45
>>
>> I cannot reproduce this build error. (I don't doubt the problem, just having a problem
>> making it happen for me.)
>> I have tried it with gcc-11.1.0, gcc-11.3.0, and gcc-13.1.0.
> 
> Which is similar to kisskb, using sh4-linux-gcc (GCC) 11.3.0...
> 
>> I'm surprised that this is the only instance that gcc found/warned about.
> 
> Indeed.
> 
>>
>> I have a patch for this one instance, but there are 40+ instances of
>>         readStatusRid()
>>         readConfigRid()
>>         readSsidRid()
>>         readStatsRid()
>>         readCapabilityRid()
>> that don't check the return status of the function calls.
>>
>> I suppose that a patch can quieten the compiler error/warning, but given
>> the 40+ other problems, it won't make the driver any noticeably better IMO.
> 
> Indeed...
> 
>>> sh4-gcc11/sh-allmodconfig
>>> seen before
>>>
>>> This is actually a real issue, and it's been here since basically forever.
>>>
>>> drivers/net/wireless/cisco/airo.c:
>>>
>>>     static int airo_get_rate(struct net_device *dev,
>>>                              struct iw_request_info *info,
>>>                              union iwreq_data *wrqu,
>>>                              char *extra)
>>>     {
>>>             struct iw_param *vwrq = &wrqu->bitrate;
>>>             struct airo_info *local = dev->ml_priv;
>>>             StatusRid status_rid;           /* Card status info */
>>>
>>>             readStatusRid(local, &status_rid, 1);
>>>
>>> ==>         vwrq->value = le16_to_cpu(status_rid.currentXmitRate) * 500000;
>>>             ...
>>>     }
>>>
>>>     static int readStatusRid(struct airo_info *ai, StatusRid *statr, int lock)
>>>     {
>>>             return PC4500_readrid(ai, RID_STATUS, statr, sizeof(*statr), lock);
>>>     }
>>>
>>>     static int PC4500_readrid(struct airo_info *ai, u16 rid, void *pBuf, int len, int lock)
>>>     {
>>>             u16 status;
>>>             int rc = SUCCESS;
>>>
>>>             if (lock) {
>>>                     if (down_interruptible(&ai->sem))
>>>                             return ERROR;
>>>
>>> pBuf output buffer contents not initialized.
>>>
>>>             }
>>>             ...
>>>     }
>>>
>>>
>>>> [1] http://kisskb.ellerman.id.au/kisskb/branch/linus/head/6995e2de6891c724bfeb2db33d7b87775f913ad1/ (all 160 configs)
>>>> [3] http://kisskb.ellerman.id.au/kisskb/branch/linus/head/45a3e24f65e90a047bef86f927ebdc4c710edaa1/ (all 160 configs)
>>
>> I appreciate the synopsis.  Here's a patch.  WDYT?
>> ---
>> From: Randy Dunlap <rdunlap@...radead.org>
>> Subject: [PATCH] wifi: airo: avoid uninitialized warning in airo_get_rate()
>>
>> Quieten a gcc (11.3.0) build error or warning by checking the function
>> call status and returning -EIO if the function call failed.
>> This is similar to what several other wireless drivers do for the
>> SIOCGIWRATE ioctl call.
>>
>> drivers/net/wireless/cisco/airo.c: error: 'status_rid.currentXmitRate' is used uninitialized [-Werror=uninitialized]
>>
>> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
>> Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
>> Reported-by: Geert Uytterhoeven <geert@...ux-m68k.org>
>> Link: lore.kernel.org/r/39abf2c7-24a-f167-91da-ed4c5435d1c4@...ux-m68k.org
>> Cc: Kalle Valo <kvalo@...nel.org>
>> Cc: linux-wireless@...r.kernel.org
>> ---
>>  drivers/net/wireless/cisco/airo.c |    5 ++++-
>>  1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff -- a/drivers/net/wireless/cisco/airo.c b/drivers/net/wireless/cisco/airo.c
>> --- a/drivers/net/wireless/cisco/airo.c
>> +++ b/drivers/net/wireless/cisco/airo.c
>> @@ -6157,8 +6157,11 @@ static int airo_get_rate(struct net_devi
>>         struct iw_param *vwrq = &wrqu->bitrate;
>>         struct airo_info *local = dev->ml_priv;
>>         StatusRid status_rid;           /* Card status info */
>> +       int ret;
>>
>> -       readStatusRid(local, &status_rid, 1);
>> +       ret = readStatusRid(local, &status_rid, 1);
>> +       if (ret)
>> +               return -EIO;
> 
> That's about the best we can do without further surgery.
> E.g. PC4500_readrid() should return a proper error code instead of
> just ERROR/SUCCESS.
> The case gcc complains about is when lock = 1 and the call to
> down_interruptible() fails, for which -EBUSY would be appropriate.

Yes, I saw that return value as one of the options.
I'll change it to that and submit it.

Thanks.
-- 
~Randy