linux-kernel - Re: [PATCH] workqueue: Fix NULL pointer dereference

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Message-ID: <29860fcc-63ed-b888-f1a0-203329ce7baa@huawei.com>
Date:   Fri, 27 Oct 2017 13:24:49 +0800
From:   Li Bin <huawei.libin@...wei.com>
To:     Lai Jiangshan <jiangshanlai@...il.com>
CC:     Tejun Heo <tj@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
        <tanxiaofei@...wei.com>, <guohanjun@...wei.com>
Subject: Re: [PATCH] workqueue: Fix NULL pointer dereference


Hi, Jiangshan

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