[PATCH v3] time/timgr: Fix wrong reference when level 0 group allocation failed

[Levi Yun <ppbuk5246@gmail.com>]

When tmigr_setup_groups() failed level 0 group allocation,
wrong reference happens on local stack array while intializing timer hierarchy.

To prevent this, Check loop condition first before initializing timer hierarchy.

Fixes: 7ee988770326 ("timers: Implement the hierarchical pull model")
Signed-off-by: Levi Yun <ppbuk5246@gmail.com>
---
v3:
    - Fix typo.

v2:
	- Modify commit message.

 kernel/time/timer_migration.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c
index ccba875d2234..84413114db5c 100644
--- a/kernel/time/timer_migration.c
+++ b/kernel/time/timer_migration.c
@@ -1596,7 +1596,7 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node)

 	} while (i < tmigr_hierarchy_levels);

-	do {
+	while (i > 0) {
 		group = stack[--i];

 		if (err < 0) {
@@ -1645,7 +1645,7 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node)
 				tmigr_connect_child_parent(child, group);
 			}
 		}
-	} while (i > 0);
+	}

 	kfree(stack);

--
2.41.0