linux-kernel - [PATCH] sched/fair: Add null pointer check to pick_next

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Message-ID: <20250320205310.779888-1-pat@patcody.io>
Date: Thu, 20 Mar 2025 13:53:10 -0700
From: Pat Cody <pat@...cody.io>
To: mingo@...hat.com
Cc: peterz@...radead.org,
	juri.lelli@...hat.com,
	vincent.guittot@...aro.org,
	dietmar.eggemann@....com,
	rostedt@...dmis.org,
	bsegall@...gle.com,
	mgorman@...e.de,
	vschneid@...hat.com,
	linux-kernel@...r.kernel.org,
	riel@...riel.com,
	patcody@...a.com,
	kernel-team@...a.com,
	stable@...r.kernel.org
Subject: [PATCH] sched/fair: Add null pointer check to pick_next_entity()

pick_eevdf() can return null, resulting in a null pointer dereference
crash in pick_next_entity()

The other call site of pick_eevdf() can already handle a null pointer,
and pick_next_entity() can already return null as well. Add an extra
check to handle the null return here.

Cc: stable@...r.kernel.org
Fixes: f12e148892ed ("sched/fair: Prepare pick_next_task() for delayed dequeue")
Signed-off-by: Pat Cody <pat@...cody.io>
---
 kernel/sched/fair.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a553181dc764..f2157298cbce 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5560,6 +5560,8 @@ pick_next_entity(struct rq *rq, struct cfs_rq *cfs_rq)
 	}
 
 	struct sched_entity *se = pick_eevdf(cfs_rq);
+	if (!se)
+		return NULL;
 	if (se->sched_delayed) {
 		dequeue_entities(rq, se, DEQUEUE_SLEEP | DEQUEUE_DELAYED);
 		/*
-- 
2.47.1