Re: [PATCH v3] workqueue: Fix double kfree for rescuer
From: Zhang, Qiang
Date: Tue May 26 2020 - 06:04:54 EST
Thank you reply
There is something wrong with my description. is it feasible to describe as follows:
The resucer is already free in "destroy_workqueue" and
"wq->rescuer = NULL" was executed, but in "rcu_free_wq"
it's release again (equivalent to kfree(NULL)), this is
unnecessary, so should remove.
On 5/26/20 4:56 PM, Lai Jiangshan wrote:
> On Mon, May 25, 2020 at 5:22 PM <qiang.zhang@xxxxxxxxxxxxx> wrote:
>> From: Zhang Qiang <qiang.zhang@xxxxxxxxxxxxx>
>> The callback function "rcu_free_wq" could be called after memory
>> was released for "rescuer" already, Thus delete a misplaced call
>> of the function "kfree".
> wq->rescuer is guaranteed to be NULL in rcu_free_wq()
> since def98c84b6cd
> ("workqueue: Fix spurious sanity check failures in destroy_workqueue()")
> And the resucer is already free in destroy_workqueue()
> since 8efe1223d73c
> ("workqueue: Fix missing kfree(rescuer) in destroy_workqueue()")
> The patch is a cleanup to remove a "kfree(NULL);".
> But the changelog is misleading.
>> Fixes: 6ba94429c8e7 ("workqueue: Reorder sysfs code")
> It is totally unrelated.
>> Signed-off-by: Zhang Qiang <qiang.zhang@xxxxxxxxxxxxx>
>> Only commit information modification.
>> kernel/workqueue.c | 1 -
>> 1 file changed, 1 deletion(-)
>> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
>> index 891ccad5f271..a2451cdcd503 100644
>> --- a/kernel/workqueue.c
>> +++ b/kernel/workqueue.c
>> @@ -3491,7 +3491,6 @@ static void rcu_free_wq(struct rcu_head *rcu)
>> - kfree(wq->rescuer);