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, 39 insertions, 0 deletions

diff --git a/drivers/video/fbdev/pxa3xx-gcu.h b/drivers/video/fbdev/pxa3xx-gcu.h
new file mode 100644
index 000000000..ea9489d16
--- /dev/null
+++ b/drivers/video/fbdev/pxa3xx-gcu.h
@@ -0,0 +1,39 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __PXA3XX_GCU_H__
+#define __PXA3XX_GCU_H__
+
+#include <linux/types.h>
+
+/* Number of 32bit words in display list (ring buffer). */
+#define PXA3XX_GCU_BUFFER_WORDS  ((256 * 1024 - 256) / 4)
+
+/* To be increased when breaking the ABI */
+#define PXA3XX_GCU_SHARED_MAGIC  0x30000001
+
+#define PXA3XX_GCU_BATCH_WORDS   8192
+
+struct pxa3xx_gcu_shared {
+	u32            buffer[PXA3XX_GCU_BUFFER_WORDS];
+
+	bool           hw_running;
+
+	unsigned long  buffer_phys;
+
+	unsigned int   num_words;
+	unsigned int   num_writes;
+	unsigned int   num_done;
+	unsigned int   num_interrupts;
+	unsigned int   num_wait_idle;
+	unsigned int   num_wait_free;
+	unsigned int   num_idle;
+
+	u32            magic;
+};
+
+/* Initialization and synchronization.
+ * Hardware is started upon write(). */
+#define PXA3XX_GCU_IOCTL_RESET		_IO('G', 0)
+#define PXA3XX_GCU_IOCTL_WAIT_IDLE	_IO('G', 2)
+
+#endif /* __PXA3XX_GCU_H__ */
+