From d2abce95a88855800db0ed7fe3f8fe6b8eec642e Mon Sep 17 00:00:00 2001
From: "Huang, Ying" <ying.huang@intel.com>
Date: Tue, 22 Mar 2022 08:39:22 +0100
Subject: [PATCH] sched/numa: Fix boot crash on arm64 systems

References: jsc#PED-827
Patch-mainline: v5.18-rc1
Git-commit: ab31c7fd2d37bc3580d9d712d5f2dfb69901fca9

Qian Cai reported a boot crash on arm64 systems, caused by:

  0fb3978b0aac ("sched/numa: Fix NUMA topology for systems with CPU-less nodes")

The bug is that node_state() must be supplied a valid node_states[] array index,
but in task_numa_placement() the max_nid search can fail with NUMA_NO_NODE,
which is not a valid index.

Fix it by checking that max_nid is a valid index.

[ mingo: Added changelog. ]

Fixes: 0fb3978b0aac ("sched/numa: Fix NUMA topology for systems with CPU-less nodes")
Reported-by: Qian Cai <quic_qiancai@quicinc.com>
Tested-by: Qian Cai <quic_qiancai@quicinc.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 kernel/sched/fair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 4b0e05e83878..c37ca12c2592 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2504,7 +2504,7 @@ static void task_numa_placement(struct task_struct *p)
 	}
 
 	/* Cannot migrate task to CPU-less node */
-	if (!node_state(max_nid, N_CPU)) {
+	if (max_nid != NUMA_NO_NODE && !node_state(max_nid, N_CPU)) {
 		int near_nid = max_nid;
 		int distance, near_distance = INT_MAX;