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, 26 insertions, 0 deletions

diff --git a/drivers/video/fbdev/vt8500lcdfb.h b/drivers/video/fbdev/vt8500lcdfb.h
new file mode 100644
index 000000000..7808f8475
--- /dev/null
+++ b/drivers/video/fbdev/vt8500lcdfb.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ *  linux/drivers/video/vt8500lcdfb.h
+ *
+ *  Copyright (C) 2010 Alexey Charkov <alchark@gmail.com>
+ */
+
+struct vt8500lcd_info {
+	struct fb_info		fb;
+	void __iomem		*regbase;
+	void __iomem		*palette_cpu;
+	dma_addr_t		palette_phys;
+	size_t			palette_size;
+	wait_queue_head_t	wait;
+};
+
+static int bpp_values[] = {
+	1,
+	2,
+	4,
+	8,
+	12,
+	16,
+	18,
+	24,
+};