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, 55 insertions, 0 deletions

diff --git a/drivers/media/dvb-frontends/drxd.h b/drivers/media/dvb-frontends/drxd.h
new file mode 100644
index 000000000..ba54fd9ad
--- /dev/null
+++ b/drivers/media/dvb-frontends/drxd.h
@@ -0,0 +1,55 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * drxd.h: DRXD DVB-T demodulator driver
+ *
+ * Copyright (C) 2005-2007 Micronas
+ */
+
+#ifndef _DRXD_H_
+#define _DRXD_H_
+
+#include <linux/types.h>
+#include <linux/i2c.h>
+
+struct drxd_config {
+	u8 index;
+
+	u8 pll_address;
+	u8 pll_type;
+#define DRXD_PLL_NONE     0
+#define DRXD_PLL_DTT7520X 1
+#define DRXD_PLL_MT3X0823 2
+
+	u32 clock;
+	u8 insert_rs_byte;
+
+	u8 demod_address;
+	u8 demoda_address;
+	u8 demod_revision;
+
+	/* If the tuner is not behind an i2c gate, be sure to flip this bit
+	   or else the i2c bus could get wedged */
+	u8 disable_i2c_gate_ctrl;
+
+	u32 IF;
+	 s16(*osc_deviation) (void *priv, s16 dev, int flag);
+};
+
+#if IS_REACHABLE(CONFIG_DVB_DRXD)
+extern
+struct dvb_frontend *drxd_attach(const struct drxd_config *config,
+				 void *priv, struct i2c_adapter *i2c,
+				 struct device *dev);
+#else
+static inline
+struct dvb_frontend *drxd_attach(const struct drxd_config *config,
+				 void *priv, struct i2c_adapter *i2c,
+				 struct device *dev)
+{
+	printk(KERN_INFO "%s: not probed - driver disabled by Kconfig\n",
+	       __func__);
+	return NULL;
+}
+#endif
+
+#endif