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, 31 insertions, 0 deletions

diff --git a/drivers/media/dvb-frontends/ec100.h b/drivers/media/dvb-frontends/ec100.h
new file mode 100644
index 000000000..398dba65f
--- /dev/null
+++ b/drivers/media/dvb-frontends/ec100.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * E3C EC100 demodulator driver
+ *
+ * Copyright (C) 2009 Antti Palosaari <crope@iki.fi>
+ */
+
+#ifndef EC100_H
+#define EC100_H
+
+#include <linux/dvb/frontend.h>
+
+struct ec100_config {
+	/* demodulator's I2C address */
+	u8 demod_address;
+};
+
+
+#if IS_REACHABLE(CONFIG_DVB_EC100)
+extern struct dvb_frontend *ec100_attach(const struct ec100_config *config,
+	struct i2c_adapter *i2c);
+#else
+static inline struct dvb_frontend *ec100_attach(
+	const struct ec100_config *config, struct i2c_adapter *i2c)
+{
+	pr_warn("%s: driver disabled by Kconfig\n", __func__);
+	return NULL;
+}
+#endif
+
+#endif /* EC100_H */