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, 75 insertions, 0 deletions

diff --git a/drivers/media/dvb-frontends/drxk.h b/drivers/media/dvb-frontends/drxk.h
new file mode 100644
index 000000000..69fdca00f
--- /dev/null
+++ b/drivers/media/dvb-frontends/drxk.h
@@ -0,0 +1,75 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _DRXK_H_
+#define _DRXK_H_
+
+#include <linux/types.h>
+#include <linux/i2c.h>
+
+/**
+ * struct drxk_config - Configure the initial parameters for DRX-K
+ *
+ * @adr:		I2C address of the DRX-K
+ * @parallel_ts:	True means that the device uses parallel TS,
+ *			Serial otherwise.
+ * @dynamic_clk:	True means that the clock will be dynamically
+ *			adjusted. Static clock otherwise.
+ * @enable_merr_cfg:	Enable SIO_PDR_PERR_CFG/SIO_PDR_MVAL_CFG.
+ * @single_master:	Device is on the single master mode
+ * @no_i2c_bridge:	Don't switch the I2C bridge to talk with tuner
+ * @antenna_gpio:	GPIO bit used to control the antenna
+ * @antenna_dvbt:	GPIO bit for changing antenna to DVB-C. A value of 1
+ *			means that 1=DVBC, 0 = DVBT. Zero means the opposite.
+ * @mpeg_out_clk_strength: DRXK Mpeg output clock drive strength.
+ * @chunk_size:		maximum size for I2C messages
+ * @microcode_name:	Name of the firmware file with the microcode
+ * @qam_demod_parameter_count:	The number of parameters used for the command
+ *				to set the demodulator parameters. All
+ *				firmwares are using the 2-parameter command.
+ *				An exception is the ``drxk_a3.mc`` firmware,
+ *				which uses the 4-parameter command.
+ *				A value of 0 (default) or lower indicates that
+ *				the correct number of parameters will be
+ *				automatically detected.
+ *
+ * On the ``*_gpio`` vars, bit 0 is UIO-1, bit 1 is UIO-2 and bit 2 is
+ * UIO-3.
+ */
+struct drxk_config {
+	u8	adr;
+	bool	single_master;
+	bool	no_i2c_bridge;
+	bool	parallel_ts;
+	bool	dynamic_clk;
+	bool	enable_merr_cfg;
+
+	bool	antenna_dvbt;
+	u16	antenna_gpio;
+
+	u8	mpeg_out_clk_strength;
+	int	chunk_size;
+
+	const char	*microcode_name;
+	int		 qam_demod_parameter_count;
+};
+
+#if IS_REACHABLE(CONFIG_DVB_DRXK)
+/**
+ * drxk_attach - Attach a drxk demod
+ *
+ * @config: pointer to &struct drxk_config with demod configuration.
+ * @i2c: i2c adapter to use.
+ *
+ * return: FE pointer on success, NULL on failure.
+ */
+extern struct dvb_frontend *drxk_attach(const struct drxk_config *config,
+					struct i2c_adapter *i2c);
+#else
+static inline struct dvb_frontend *drxk_attach(const struct drxk_config *config,
+					struct i2c_adapter *i2c)
+{
+	printk(KERN_WARNING "%s: driver disabled by Kconfig\n", __func__);
+	return NULL;
+}
+#endif
+
+#endif