Re: [PATCH] workqueue: Fix NULL pointer dereference

[Li Bin]

Hi, Jiangshan

on 2017/10/26 23:55, Lai Jiangshan wrote:
> On Tue, Oct 24, 2017 at 9:18 AM, Li Bin <huawei.libin@xxxxxxxxxx> wrote:

> 
> I remember that softirq can be invoked when irq_eixt(),
> and in this case the current->current_pwq is also NULL
> if __queue_work() is called in the soft irq.
> 
> So in_task() might be better than !in_irq() for the fix?
> 

Good catch, I will fix it and resend the patch.

Thanks,
Li Bin

>> |-schedule()
>> ----------------------------------------------------------------
>>
>> Avoid it by checking for irq context in current_wq_worker(), and
>> if in irq context, we shouldn't use the 'current' to check the
>> condition.
>>
>> Reported-by: Xiaofei Tan <tanxiaofei@xxxxxxxxxx>
>> Signed-off-by: Li Bin <huawei.libin@xxxxxxxxxx>
>> ---
>>  kernel/workqueue_internal.h | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/workqueue_internal.h b/kernel/workqueue_internal.h
>> index 8635417..d81cb9b 100644
>> --- a/kernel/workqueue_internal.h
>> +++ b/kernel/workqueue_internal.h
>> @@ -9,6 +9,7 @@
>>
>>  #include <linux/workqueue.h>
>>  #include <linux/kthread.h>
>> +#include <linux/preempt.h>
>>
>>  struct worker_pool;
>>
>> @@ -59,7 +60,7 @@ struct worker {
>>   */
>>  static inline struct worker *current_wq_worker(void)
>>  {
>> -       if (current->flags & PF_WQ_WORKER)
>> +       if (!in_irq() && (current->flags & PF_WQ_WORKER))
>>                 return kthread_data(current);
>>         return NULL;
>>  }
>> --
>> 1.7.12.4
>>
> 
> .
>