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, 54 insertions, 0 deletions

diff --git a/drivers/media/dvb-frontends/stv0288.h b/drivers/media/dvb-frontends/stv0288.h
new file mode 100644
index 000000000..8690aa61b
--- /dev/null
+++ b/drivers/media/dvb-frontends/stv0288.h
@@ -0,0 +1,54 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+	Driver for ST STV0288 demodulator
+
+	Copyright (C) 2006 Georg Acher, BayCom GmbH, acher (at) baycom (dot) de
+		for Reel Multimedia
+	Copyright (C) 2008 TurboSight.com, <bob@turbosight.com>
+	Copyright (C) 2008 Igor M. Liplianin <liplianin@me.by>
+		Removed stb6000 specific tuner code and revised some
+		procedures.
+
+
+*/
+
+#ifndef STV0288_H
+#define STV0288_H
+
+#include <linux/dvb/frontend.h>
+#include <media/dvb_frontend.h>
+
+struct stv0288_config {
+	/* the demodulator's i2c address */
+	u8 demod_address;
+
+	u8* inittab;
+
+	/* minimum delay before retuning */
+	int min_delay_ms;
+
+	int (*set_ts_params)(struct dvb_frontend *fe, int is_punctured);
+};
+
+#if IS_REACHABLE(CONFIG_DVB_STV0288)
+extern struct dvb_frontend *stv0288_attach(const struct stv0288_config *config,
+					   struct i2c_adapter *i2c);
+#else
+static inline struct dvb_frontend *stv0288_attach(const struct stv0288_config *config,
+					   struct i2c_adapter *i2c)
+{
+	printk(KERN_WARNING "%s: driver disabled by Kconfig\n", __func__);
+	return NULL;
+}
+#endif /* CONFIG_DVB_STV0288 */
+
+static inline int stv0288_writereg(struct dvb_frontend *fe, u8 reg, u8 val)
+{
+	int r = 0;
+	u8 buf[] = { reg, val };
+	if (fe->ops.write)
+		r = fe->ops.write(fe, buf, 2);
+	return r;
+}
+
+#endif /* STV0288_H */