[PATCH] sched_ext: Gate cid kfuncs behind the SCX struct_ops check

[Qiurong Fang]

From: fangqiurong <fangqiurong@xxxxxxxxxx>

scx_bpf_cid_to_cpu(), scx_bpf_cpu_to_cid() and scx_bpf_cid_topo() live in
the scx_kfunc_ids_cid set, but scx_kfunc_context_filter() doesn't check
that set. The filter's first test treats any kfunc outside its known sets
as non-SCX and allows it, so these three kfuncs can be called from any
struct_ops program - e.g. a TCP congestion control program.

Add scx_kfunc_ids_cid to the filter's known sets, matching how in_any and
in_idle are handled.

Fixes: e9b55af47edf ("sched_ext: Add topological CPU IDs (cids)")
Assisted-by: Z.ai:glm-5.2
Signed-off-by: fangqiurong <fangqiurong@xxxxxxxxxx>
---
 kernel/sched/ext/cid.h | 1 +
 kernel/sched/ext/ext.c | 9 +++++----
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/ext/cid.h b/kernel/sched/ext/cid.h
index 1f74d1f331f5..2fe2311a0f99 100644
--- a/kernel/sched/ext/cid.h
+++ b/kernel/sched/ext/cid.h
@@ -67,6 +67,7 @@ extern s32 __rcu *scx_shard_node;
 extern struct scx_cid_shard __rcu *scx_cid_shard_ranges;
 extern struct scx_cid_topo __rcu *scx_cid_topo;
 extern struct btf_id_set8 scx_kfunc_ids_init_cids;
+extern struct btf_id_set8 scx_kfunc_ids_cid;
 
 void scx_cmask_clear(struct scx_cmask *m);
 void scx_cmask_fill(struct scx_cmask *m);
diff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c
index f9631e66a9fc..317eb0110c64 100644
--- a/kernel/sched/ext/ext.c
+++ b/kernel/sched/ext/ext.c
@@ -10762,19 +10762,20 @@ int scx_kfunc_context_filter(const struct bpf_prog *prog, u32 kfunc_id)
 	bool in_idle = btf_id_set8_contains(&scx_kfunc_ids_idle, kfunc_id);
 	bool in_any = btf_id_set8_contains(&scx_kfunc_ids_any, kfunc_id);
 	bool in_cpu_only = btf_id_set8_contains(&scx_kfunc_ids_cpu_only, kfunc_id);
+	bool in_cid = btf_id_set8_contains(&scx_kfunc_ids_cid, kfunc_id);
 	u32 moff, flags;
 
 	/* Not an SCX kfunc - allow. */
 	if (!(in_unlocked || in_init_cids || in_select_cpu || in_enqueue || in_dispatch ||
-	      in_cpu_release || in_idle || in_any))
+	      in_cpu_release || in_idle || in_any || in_cid))
 		return 0;
 
 	/* SYSCALL progs (e.g. BPF test_run()) may call unlocked and select_cpu kfuncs. */
 	if (prog->type == BPF_PROG_TYPE_SYSCALL)
-		return (in_unlocked || in_select_cpu || in_idle || in_any) ? 0 : -EACCES;
+		return (in_unlocked || in_select_cpu || in_idle || in_any || in_cid) ? 0 : -EACCES;
 
 	if (prog->type != BPF_PROG_TYPE_STRUCT_OPS)
-		return (in_any || in_idle) ? 0 : -EACCES;
+		return (in_any || in_idle || in_cid) ? 0 : -EACCES;
 
 	/*
 	 * add_subprog_and_kfunc() collects all kfunc calls, including dead code
@@ -10809,7 +10810,7 @@ int scx_kfunc_context_filter(const struct bpf_prog *prog, u32 kfunc_id)
 		return -EACCES;
 
 	/* SCX struct_ops: check the per-op allow list. */
-	if (in_any || in_idle)
+	if (in_any || in_idle || in_cid)
 		return 0;
 
 	moff = prog->aux->attach_st_ops_member_off;
-- 
2.43.0