[PATCH 28/46] sched_ext: scx_dsq_move() should validate the task belongs to the right scheduler

[Tejun Heo <tj@kernel.org>]

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@kernel.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 891b956a92b6..c60b58341d24 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -6027,8 +6027,8 @@ 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;
@@ -6038,6 +6038,11 @@ static bool scx_dsq_move(struct bpf_iter_scx_dsq_kern *kit,
 	    !scx_kf_allowed(sch, SCX_KF_DISPATCH))
 		return false;
 
+	if (unlikely(sch != scx_task_sched(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
-- 
2.51.0