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, 40 insertions, 0 deletions

diff --git a/drivers/char/nwbutton.h b/drivers/char/nwbutton.h
new file mode 100644
index 000000000..f2b9fdc1f
--- /dev/null
+++ b/drivers/char/nwbutton.h
@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __NWBUTTON_H
+#define __NWBUTTON_H
+
+/*
+ * 	NetWinder Button Driver-
+ *	Copyright (C) Alex Holden <alex@linuxhacker.org> 1998, 1999.
+ */
+
+#ifdef __NWBUTTON_C	/* Actually compiling the driver itself */
+
+/* Various defines: */
+
+#define NUM_PRESSES_REBOOT 2	/* How many presses to activate shutdown */
+#define BUTTON_DELAY 30 	/* How many jiffies for sequence to end */
+#define VERSION "0.3"		/* Driver version number */
+
+/* Structure definitions: */
+
+struct button_callback {
+	void (*callback) (void);
+	int count;
+};
+
+/* Function prototypes: */
+
+static void button_sequence_finished(struct timer_list *unused);
+static irqreturn_t button_handler (int irq, void *dev_id);
+int button_init (void);
+int button_add_callback (void (*callback) (void), int count);
+int button_del_callback (void (*callback) (void));
+static void button_consume_callbacks (int bpcount);
+
+#else /* Not compiling the driver itself */
+
+extern int button_add_callback (void (*callback) (void), int count);
+extern int button_del_callback (void (*callback) (void));
+
+#endif /* __NWBUTTON_C */
+#endif /* __NWBUTTON_H */