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, 38 insertions, 0 deletions

diff --git a/drivers/media/dvb-frontends/isl6421.h b/drivers/media/dvb-frontends/isl6421.h
new file mode 100644
index 000000000..e59487784
--- /dev/null
+++ b/drivers/media/dvb-frontends/isl6421.h
@@ -0,0 +1,38 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * isl6421.h - driver for lnb supply and control ic ISL6421
+ *
+ * Copyright (C) 2006 Andrew de Quincey
+ * Copyright (C) 2006 Oliver Endriss
+ *
+ * the project's page is at https://linuxtv.org
+ */
+
+#ifndef _ISL6421_H
+#define _ISL6421_H
+
+#include <linux/dvb/frontend.h>
+
+/* system register bits */
+#define ISL6421_OLF1	0x01
+#define ISL6421_EN1	0x02
+#define ISL6421_VSEL1	0x04
+#define ISL6421_LLC1	0x08
+#define ISL6421_ENT1	0x10
+#define ISL6421_ISEL1	0x20
+#define ISL6421_DCL	0x40
+
+#if IS_REACHABLE(CONFIG_DVB_ISL6421)
+/* override_set and override_clear control which system register bits (above) to always set & clear */
+extern struct dvb_frontend *isl6421_attach(struct dvb_frontend *fe, struct i2c_adapter *i2c, u8 i2c_addr,
+			  u8 override_set, u8 override_clear, bool override_tone);
+#else
+static inline struct dvb_frontend *isl6421_attach(struct dvb_frontend *fe, struct i2c_adapter *i2c, u8 i2c_addr,
+						  u8 override_set, u8 override_clear, bool override_tone)
+{
+	printk(KERN_WARNING "%s: driver disabled by Kconfig\n", __func__);
+	return NULL;
+}
+#endif // CONFIG_DVB_ISL6421
+
+#endif