[PATCH v2 1/2] Ensure sched_domains_numa_levels safe in other functions.

We should temporarily reset sched_domains_numa_levels to 0 after
it is reset to 'level' in sched_init_numa(). If it fails to allocate
memory for array sched_domains_numa_masks[][], the array will contain
less then 'level' members. This could be dangerous when we use it to
iterate array sched_domains_numa_masks[][] in other functions.

This patch set sched_domains_numa_levels to 0 before initializing
array sched_domains_numa_masks[][], and reset it to 'level' when
sched_domains_numa_masks[][] is fully initialized.

Signed-off-by: Tang Chen <[email protected]>
Signed-off-by: Wen Congyang <[email protected]>
---
 kernel/sched/core.c |   13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 649c9f8..3aa306a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6660,6 +6660,17 @@ static void sched_init_numa(void)
 	 * numbers.
 	 */
 
+	/*
+	 * Here, we should temporarily reset sched_domains_numa_levels to 0.
+	 * If it fails to allocate memory for array sched_domains_numa_masks[][],
+	 * the array will contain less then 'level' members. This could be
+	 * dangerous when we use it to iterate array sched_domains_numa_masks[][]
+	 * in other functions.
+	 *
+	 * We reset it to 'level' at the end of this function.
+	 */
+	sched_domains_numa_levels = 0;
+
 	sched_domains_numa_masks = kzalloc(sizeof(void *) * level, GFP_KERNEL);
 	if (!sched_domains_numa_masks)
 		return;
@@ -6714,6 +6725,8 @@ static void sched_init_numa(void)
 	}
 
 	sched_domain_topology = tl;
+
+	sched_domains_numa_levels = level;
 }
 #else
 static inline void sched_init_numa(void)
-- 
1.7.10.1