selftests/bpf: Reject graph kptr use after RCU unlockgrafted

Add a sleepable verifier test that loads a graph-node local kptr in an
explicit RCU read-side critical section, then passes its node to
bpf_rbtree_remove() after the section ends.

Before the verifier fix, the stale NON_OWN_REF flag makes the node look like
a live borrowed reference and the program is accepted. After the fix, the
pointer is demoted without NON_OWN_REF and the graph kfunc argument is
rejected.

Also exercise a graph kptr loaded while a spin lock provides implicit RCU
protection. The pointer must be invalidated when the lock is released, which
guards the required ordering between non-owning-reference invalidation and
RCU demotion.

Update the existing fault-protected load test state description. The
post-unlock pointer no longer carries NON_OWN_REF, but remains readable
because the load is rewritten to use BPF_PROBE_MEM.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 18 insertions, 0 deletions

diff --git a/drivers/mfd/rsmu.h b/drivers/mfd/rsmu.h
new file mode 100644
index 000000000..1bb04cafa
--- /dev/null
+++ b/drivers/mfd/rsmu.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Renesas Synchronization Management Unit (SMU) devices.
+ *
+ * Copyright (C) 2021 Integrated Device Technology, Inc., a Renesas Company.
+ */
+
+#ifndef __RSMU_MFD_H
+#define __RSMU_MFD_H
+
+#include <linux/mfd/rsmu.h>
+
+#define RSMU_CM_SCSR_BASE		0x20100000
+
+int rsmu_core_init(struct rsmu_ddata *rsmu);
+void rsmu_core_exit(struct rsmu_ddata *rsmu);
+
+#endif /* __RSMU_MFD_H */