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/media/dvb-frontends/lnbh25.h b/drivers/media/dvb-frontends/lnbh25.h
new file mode 100644
index 000000000..4f68f0c44
--- /dev/null
+++ b/drivers/media/dvb-frontends/lnbh25.h
@@ -0,0 +1,46 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * lnbh25.c
+ *
+ * Driver for LNB supply and control IC LNBH25
+ *
+ * Copyright (C) 2014 NetUP Inc.
+ * Copyright (C) 2014 Sergey Kozlov <serjk@netup.ru>
+ * Copyright (C) 2014 Abylay Ospan <aospan@netup.ru>
+ */
+
+#ifndef LNBH25_H
+#define LNBH25_H
+
+#include <linux/i2c.h>
+#include <linux/dvb/frontend.h>
+
+/* 22 kHz tone enabled. Tone output controlled by DSQIN pin */
+#define	LNBH25_TEN	0x01
+/* Low power mode activated (used only with 22 kHz tone output disabled) */
+#define LNBH25_LPM	0x02
+/* DSQIN input pin is set to receive external 22 kHz TTL signal source */
+#define LNBH25_EXTM	0x04
+
+struct lnbh25_config {
+	u8	i2c_address;
+	u8	data2_config;
+};
+
+#if IS_REACHABLE(CONFIG_DVB_LNBH25)
+struct dvb_frontend *lnbh25_attach(
+	struct dvb_frontend *fe,
+	struct lnbh25_config *cfg,
+	struct i2c_adapter *i2c);
+#else
+static inline struct dvb_frontend *lnbh25_attach(
+	struct dvb_frontend *fe,
+	struct lnbh25_config *cfg,
+	struct i2c_adapter *i2c)
+{
+	printk(KERN_WARNING "%s: driver disabled by Kconfig\n", __func__);
+	return NULL;
+}
+#endif
+
+#endif