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, 43 insertions, 0 deletions

diff --git a/drivers/media/dvb-frontends/tda8261.h b/drivers/media/dvb-frontends/tda8261.h
new file mode 100644
index 000000000..d45a102a7
--- /dev/null
+++ b/drivers/media/dvb-frontends/tda8261.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+	TDA8261 8PSK/QPSK tuner driver
+	Copyright (C) Manu Abraham (abraham.manu@gmail.com)
+
+*/
+
+#ifndef __TDA8261_H
+#define __TDA8261_H
+
+enum tda8261_step {
+	TDA8261_STEP_2000 = 0,	/* 2000 kHz */
+	TDA8261_STEP_1000,	/* 1000 kHz */
+	TDA8261_STEP_500,	/*  500 kHz */
+	TDA8261_STEP_250,	/*  250 kHz */
+	TDA8261_STEP_125	/*  125 kHz */
+};
+
+struct tda8261_config {
+//	u8			buf[16];
+	u8			addr;
+	enum tda8261_step	step_size;
+};
+
+#if IS_REACHABLE(CONFIG_DVB_TDA8261)
+
+extern struct dvb_frontend *tda8261_attach(struct dvb_frontend *fe,
+					   const struct tda8261_config *config,
+					   struct i2c_adapter *i2c);
+
+#else
+
+static inline struct dvb_frontend *tda8261_attach(struct dvb_frontend *fe,
+						  const struct tda8261_config *config,
+						  struct i2c_adapter *i2c)
+{
+	printk(KERN_WARNING "%s: Driver disabled by Kconfig\n", __func__);
+	return NULL;
+}
+
+#endif //CONFIG_DVB_TDA8261
+
+#endif// __TDA8261_H