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, 42 insertions, 0 deletions

diff --git a/drivers/media/dvb-frontends/stv0910.h b/drivers/media/dvb-frontends/stv0910.h
new file mode 100644
index 000000000..0b6f02ad7
--- /dev/null
+++ b/drivers/media/dvb-frontends/stv0910.h
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Driver for the ST STV0910 DVB-S/S2 demodulator.
+ *
+ * Copyright (C) 2014-2015 Ralph Metzler <rjkm@metzlerbros.de>
+ *                         Marcus Metzler <mocm@metzlerbros.de>
+ *                         developed for Digital Devices GmbH
+ */
+
+#ifndef _STV0910_H_
+#define _STV0910_H_
+
+#include <linux/types.h>
+#include <linux/i2c.h>
+
+struct stv0910_cfg {
+	u32 clk;
+	u8  adr;
+	u8  parallel;
+	u8  rptlvl;
+	u8  single;
+	u8  tsspeed;
+};
+
+#if IS_REACHABLE(CONFIG_DVB_STV0910)
+
+struct dvb_frontend *stv0910_attach(struct i2c_adapter *i2c,
+				    struct stv0910_cfg *cfg, int nr);
+
+#else
+
+static inline struct dvb_frontend *stv0910_attach(struct i2c_adapter *i2c,
+						  struct stv0910_cfg *cfg,
+						  int nr)
+{
+	pr_warn("%s: driver disabled by Kconfig\n", __func__);
+	return NULL;
+}
+
+#endif /* CONFIG_DVB_STV0910 */
+
+#endif /* _STV0910_H_ */