Re: rcu_read_lock/unlock protect find_task_by_vpid call in migrate_pages

[KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>]

Hi

> Signed-off-by: Dave Jones <davej@redhat.com>
> 
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 4a57f13..2f0f55b 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -1308,6 +1308,7 @@ SYSCALL_DEFINE4(migrate_pages, pid_t, pid, unsigned long, maxnode,
>  
>  	/* Find the mm_struct */
>  	read_lock(&tasklist_lock);
> +	rcu_read_lock();
>  	task = pid ? find_task_by_vpid(pid) : current;
>  	if (!task) {
>  		read_unlock(&tasklist_lock);
> @@ -1315,6 +1316,7 @@ SYSCALL_DEFINE4(migrate_pages, pid_t, pid, unsigned long, maxnode,
>  		goto out;
>  	}
>  	mm = get_task_mm(task);
> +	rcu_read_unlock();
>  	read_unlock(&tasklist_lock);
>  
>  	err = -EINVAL;

Thanks reporting. but mmotm seems already has the same patch.