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, 52 insertions, 0 deletions

diff --git a/drivers/media/dvb-frontends/dib3000.h b/drivers/media/dvb-frontends/dib3000.h
new file mode 100644
index 000000000..3f129efa2
--- /dev/null
+++ b/drivers/media/dvb-frontends/dib3000.h
@@ -0,0 +1,52 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * public header file of the frontend drivers for mobile DVB-T demodulators
+ * DiBcom 3000M-B and DiBcom 3000P/M-C (http://www.dibcom.fr/)
+ *
+ * Copyright (C) 2004-5 Patrick Boettcher (patrick.boettcher@posteo.de)
+ *
+ * based on GPL code from DibCom, which has
+ *
+ * Copyright (C) 2004 Amaury Demol for DiBcom
+ *
+ * Acknowledgements
+ *
+ *  Amaury Demol from DiBcom for providing specs and driver
+ *  sources, on which this driver (and the dvb-dibusb) are based.
+ *
+ * see Documentation/driver-api/media/drivers/dvb-usb.rst for more information
+ */
+
+#ifndef DIB3000_H
+#define DIB3000_H
+
+#include <linux/dvb/frontend.h>
+
+struct dib3000_config
+{
+	/* the demodulator's i2c address */
+	u8 demod_address;
+};
+
+struct dib_fe_xfer_ops
+{
+	/* pid and transfer handling is done in the demodulator */
+	int (*pid_parse)(struct dvb_frontend *fe, int onoff);
+	int (*fifo_ctrl)(struct dvb_frontend *fe, int onoff);
+	int (*pid_ctrl)(struct dvb_frontend *fe, int index, int pid, int onoff);
+	int (*tuner_pass_ctrl)(struct dvb_frontend *fe, int onoff, u8 pll_ctrl);
+};
+
+#if IS_REACHABLE(CONFIG_DVB_DIB3000MB)
+extern struct dvb_frontend* dib3000mb_attach(const struct dib3000_config* config,
+					     struct i2c_adapter* i2c, struct dib_fe_xfer_ops *xfer_ops);
+#else
+static inline struct dvb_frontend* dib3000mb_attach(const struct dib3000_config* config,
+					     struct i2c_adapter* i2c, struct dib_fe_xfer_ops *xfer_ops)
+{
+	printk(KERN_WARNING "%s: driver disabled by Kconfig\n", __func__);
+	return NULL;
+}
+#endif // CONFIG_DVB_DIB3000MB
+
+#endif // DIB3000_H