FAILED: patch "[PATCH] sched/fair: Use RCU accessors consistently for ->numa_group" failed to apply to 4.4-stable tree

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From cb361d8cdef69990f6b4504dc1fd9a594d983c97 Mon Sep 17 00:00:00 2001
From: Jann Horn <[email protected]>
Date: Tue, 16 Jul 2019 17:20:47 +0200
Subject: [PATCH] sched/fair: Use RCU accessors consistently for ->numa_group

The old code used RCU annotations and accessors inconsistently for ->numa_group, which can lead to use-after-frees and NULL dereferences.

Let all accesses to ->numa_group use proper RCU helpers to prevent such issues.

index 8dc1811487f5..9f51932bd543 100644
@@ -1092,7 +1092,15 @@ struct task_struct {
 	u64				last_sum_exec_runtime;
 	struct callback_head		numa_work;
 
-	struct numa_group		*numa_group;
+	/*
+	 * This pointer is only modified for current in syscall and
+	 * pagefault context (and for tasks being destroyed), so it can be read
+	 * from any of the following contexts:
+	 *  - RCU read-side critical section
+	 *  - current->numa_group from everywhere
+	 *  - task's runqueue locked, task not running
+	 */
+	struct numa_group __rcu		*numa_group;
 
 	/*
 	 * numa_faults is an array split into four regions: