Subject: Re: [PATCH] b43legacy: Fix a sleep-in-atomic bug in b43legacy_attr_interfmode_store

From: Jia-Ju Bai <baijiaju1990-9Onoh4P/[email-masked]>
Date: Thu, 01 Jun 2017 09:05:07 +0800

On 06/01/2017 01:33 AM, Larry Finger wrote:
> On 05/31/2017 05:29 AM, Jia-Ju Bai wrote:
>> The driver may sleep under a spin lock, and the function call path is:
>> b43legacy_attr_interfmode_store (acquire the lock by spin_lock_irqsave)
>>    b43legacy_radio_set_interference_mitigation
>>      b43legacy_radio_interference_mitigation_disable
>>        b43legacy_calc_nrssi_slope
>>          b43legacy_synth_pu_workaround
>>            might_sleep and msleep --> may sleep
>>
>> Fixing it may be complex, and a possible way is to remove
>> spin_lock_irqsave and spin_lock_irqrestore in
>> b43legacy_attr_interfmode_store, and the code has been protected by
>> mutex_lock and mutex_unlock.
>>
>> Signed-off-by: Jia-Ju Bai <baijiaju1990-9Onoh4P/[email-masked]>
>> ---
>>   drivers/net/wireless/broadcom/b43legacy/sysfs.c |    2 --
>>   1 file changed, 2 deletions(-)
>>
>> diff --git a/drivers/net/wireless/broadcom/b43legacy/sysfs.c 
>> b/drivers/net/wireless/broadcom/b43legacy/sysfs.c
>> index 2a1da15..9ede143 100644
>> --- a/drivers/net/wireless/broadcom/b43legacy/sysfs.c
>> +++ b/drivers/net/wireless/broadcom/b43legacy/sysfs.c
>> @@ -137,14 +137,12 @@ static ssize_t 
>> b43legacy_attr_interfmode_store(struct device *dev,
>>       }
>>         mutex_lock(&wldev->wl->mutex);
>> -    spin_lock_irqsave(&wldev->wl->irq_lock, flags);
>>         err = b43legacy_radio_set_interference_mitigation(wldev, mode);
>>       if (err)
>>           b43legacyerr(wldev->wl, "Interference Mitigation not "
>>                  "supported by device\n");
>>       mmiowb();
>> -    spin_unlock_irqrestore(&wldev->wl->irq_lock, flags);
>>       mutex_unlock(&wldev->wl->mutex);
>>         return err ? err : count;
>>
>
> Jia-Ju,
>
> Did you actually observe the attempt to sleep under the spin lock, or 
> did you discover this using some tool? In other words, have either of 
> your patches been tested?
>
> Larry
>
Hi,

In fact, my reported bugs are found by a static analysis tool written by 
me, and they are checked by my review of the driver code.
I admit my patches are not well tested, and they may not well fix the bugs.
I am looking forward to opinions and suggestions :)

Thanks,
Jia-Ju Bai