[Devel] [PATCH RHEL8 COMMIT] ve,kthread: fix use-after-return.

[Konstantin Khorenko]

The commit is pushed to "branch-rh8-4.18.0-80.1.2.vz8.2.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh8-4.18.0-80.1.2.vz8.2.1
------>
commit cb8ab0c4e0f01aeca3fda6baf6190e5220b36818
Author: Andrey Ryabinin <aryabinin at virtuozzo.com>
Date:   Fri Oct 18 11:59:19 2019 +0300

    ve,kthread: fix use-after-return.
    
    __kthread_create_ve() passes pointer to the data on stack to
    another thread, and return immidiately causing use-after-return.
    
    Fix this by moving all in upper function which waits
    another thread finishes it's job.
    
    https://jira.sw.ru/browse/PSBM-93708
    Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
---
 kernel/kthread.c | 23 ++++++++---------------
 1 file changed, 8 insertions(+), 15 deletions(-)

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 4ba351b3cf66..68c49a397c6a 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -303,19 +303,6 @@ static void kthread_create_fn(struct kthread_work *w)
 	create_kthread_flags(work->info, work->flags);
 }
 
-static void __kthread_create_ve(struct kthread_create_info *create,
-			        struct ve_struct *ve,
-				unsigned long flags)
-{
-	struct kthread_create_work work = {
-		KTHREAD_WORK_INIT(work.work, kthread_create_fn),
-		.info = create,
-		.flags = flags,
-	};
-
-	kthread_queue_work(ve->kthreadd_worker, &work.work);
-	return;
-}
 #endif
 static void kthread_create_add(struct kthread_create_info *create)
 {
@@ -335,6 +322,9 @@ struct task_struct *__kthread_create_on_node_ve(struct ve_struct *ve,
 						va_list args)
 {
 	DECLARE_COMPLETION_ONSTACK(done);
+	struct kthread_create_work work = {
+		KTHREAD_WORK_INIT(work.work, kthread_create_fn),
+	};
 	struct task_struct *task;
 	struct kthread_create_info *create = kmalloc(sizeof(*create),
 						     GFP_KERNEL);
@@ -348,8 +338,11 @@ struct task_struct *__kthread_create_on_node_ve(struct ve_struct *ve,
 
 #ifdef CONFIG_VE
 	if (!ve_is_super(ve))
-		__kthread_create_ve(create, ve, flags);
-	else
+	{
+		work.info = create;
+		work.flags = flags;
+		kthread_queue_work(ve->kthreadd_worker, &work.work);
+	} else
 #endif
 		kthread_create_add(create);
 	/*