Re: [PATCH] staging: rtl8723bs: Fix two possible sleep-in-atomic-context bugs in translate_scan()

[Jia-Ju Bai <baijiaju1990@gmail.com>]

On 2018/6/20 17:56, Dan Carpenter wrote:
> On Wed, Jun 20, 2018 at 05:50:16PM +0800, Jia-Ju Bai wrote:
>> The driver may sleep with holding a spinlock.
>> The function call paths (from bottom to top) in Linux-4.16.7 are:
>>
>> [FUNC] kzalloc(GFP_KERNEL)
>> drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 323:
>> 		kzalloc in translate_scan
>> drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 1554:
>> 		translate_scan in rtw_wx_get_scan
>> drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 1533:
>> 		spin_lock_bh in rtw_wx_get_scan
>>
>> [FUNC] kzalloc(GFP_KERNEL)
>> drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 455:
>> 		kzalloc in translate_scan
>> drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 1554:
>> 		translate_scan in rtw_wx_get_scan
>> drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 1533:
>> 		spin_lock_bh in rtw_wx_get_scan
>>
>> To fix these bugs, GFP_KERNEL is replaced with GFP_ATOMIC.
>>
>> These bugs are found by my static analysis tool (DSAC-2) and checked by
>> my code review.
>>
>> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
>> ---
>>   drivers/staging/rtl8723bs/os_dep/ioctl_linux.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/staging/rtl8723bs/os_dep/ioctl_linux.c b/drivers/staging/rtl8723bs/os_dep/ioctl_linux.c
>> index b26533983864..7632b8974563 100644
>> --- a/drivers/staging/rtl8723bs/os_dep/ioctl_linux.c
>> +++ b/drivers/staging/rtl8723bs/os_dep/ioctl_linux.c
>> @@ -321,7 +321,7 @@ static char *translate_scan(struct adapter *padapter,
>>   		RT_TRACE(_module_rtl871x_mlme_c_, _drv_info_, ("rtw_wx_get_scan: ssid =%s\n", pnetwork->network.Ssid.Ssid));
>>   		RT_TRACE(_module_rtl871x_mlme_c_, _drv_info_, ("rtw_wx_get_scan: wpa_len =%d rsn_len =%d\n", wpa_len, rsn_len));
>>   
>> -		buf = kzalloc(MAX_WPA_IE_LEN*2, GFP_KERNEL);
>> +		buf = kzalloc(MAX_WPA_IE_LEN*2, GFP_ATOMIC);
>>   		if (!buf)
>>   			return start;
> Thanks!  It occurs to me that another way to detect this bug is that
> one of the allocations in this function already uses GFP_ATOMIC.  It
> doesn't normally make sense to mix GFP_ATOMIC and GFP_KERNEL when there
> isn't any locking in the function.

Yes, this pattern is interesting for bug finding :)
But to fix the bugs of this pattern, we need to decide whether 
GFP_ATOMIC or GFP_KERNEL should be used here.


Best wishes,
Jia-Ju Bai