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, 46 insertions, 0 deletions

diff --git a/drivers/clk/meson/parm.h b/drivers/clk/meson/parm.h
new file mode 100644
index 000000000..3c9ef1b50
--- /dev/null
+++ b/drivers/clk/meson/parm.h
@@ -0,0 +1,46 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2015 Endless Mobile, Inc.
+ * Author: Carlo Caione <carlo@endlessm.com>
+ */
+
+#ifndef __MESON_PARM_H
+#define __MESON_PARM_H
+
+#include <linux/bits.h>
+#include <linux/regmap.h>
+
+#define PMASK(width)			GENMASK(width - 1, 0)
+#define SETPMASK(width, shift)		GENMASK(shift + width - 1, shift)
+#define CLRPMASK(width, shift)		(~SETPMASK(width, shift))
+
+#define PARM_GET(width, shift, reg)					\
+	(((reg) & SETPMASK(width, shift)) >> (shift))
+#define PARM_SET(width, shift, reg, val)				\
+	(((reg) & CLRPMASK(width, shift)) | ((val) << (shift)))
+
+#define MESON_PARM_APPLICABLE(p)		(!!((p)->width))
+
+struct parm {
+	u16	reg_off;
+	u8	shift;
+	u8	width;
+};
+
+static inline unsigned int meson_parm_read(struct regmap *map, struct parm *p)
+{
+	unsigned int val;
+
+	regmap_read(map, p->reg_off, &val);
+	return PARM_GET(p->width, p->shift, val);
+}
+
+static inline void meson_parm_write(struct regmap *map, struct parm *p,
+				    unsigned int val)
+{
+	regmap_update_bits(map, p->reg_off, SETPMASK(p->width, p->shift),
+			   val << p->shift);
+}
+
+#endif /* __MESON_PARM_H */
+