linux-kernel - [PATCH 12/34] sched_ext: scx_dsq_move() should validate the task belongs to the right scheduler

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Message-ID: <20260121231140.832332-13-tj@kernel.org>
Date: Wed, 21 Jan 2026 13:11:18 -1000
From: Tejun Heo <tj@...nel.org>
To: linux-kernel@...r.kernel.org,
	sched-ext@...ts.linux.dev
Cc: void@...ifault.com,
	andrea.righi@...ux.dev,
	changwoo@...lia.com,
	emil@...alapatis.com,
	Tejun Heo <tj@...nel.org>
Subject: [PATCH 12/34] sched_ext: scx_dsq_move() should validate the task belongs to the right scheduler

scx_bpf_dsq_move[_vtime]() calls scx_dsq_move() to move task from a DSQ to
another. However, @p doesn't necessarily have to come form the containing
iteration and can thus be a task which belongs to another scx_sched. Verify
that @p is on the same scx_sched as the DSQ being iterated.

Signed-off-by: Tejun Heo <tj@...nel.org>
---
 kernel/sched/ext.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index aad3af8e8377..07cd130f62fb 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -6463,8 +6463,8 @@ static const struct btf_kfunc_id_set scx_kfunc_set_enqueue_dispatch = {
 static bool scx_dsq_move(struct bpf_iter_scx_dsq_kern *kit,
 			 struct task_struct *p, u64 dsq_id, u64 enq_flags)
 {
-	struct scx_sched *sch = scx_root;
 	struct scx_dispatch_q *src_dsq = kit->dsq, *dst_dsq;
+	struct scx_sched *sch = src_dsq->sched;
 	struct rq *this_rq, *src_rq, *locked_rq;
 	bool dispatched = false;
 	bool in_balance;
@@ -6481,6 +6481,11 @@ static bool scx_dsq_move(struct bpf_iter_scx_dsq_kern *kit,
 	if (unlikely(READ_ONCE(scx_aborting)))
 		return false;
 
+	if (unlikely(!scx_task_on_sched(sch, p))) {
+		scx_error(sch, "scx_bpf_dsq_move[_vtime]() on %s[%d] but the task belongs to a different scheduler",
+			  p->comm, p->pid);
+	}
+
 	/*
 	 * Can be called from either ops.dispatch() locking this_rq() or any
 	 * context where no rq lock is held. If latter, lock @p's task_rq which
-- 
2.52.0