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, 41 insertions, 0 deletions

diff --git a/arch/mips/cobalt/buttons.c b/arch/mips/cobalt/buttons.c
new file mode 100644
index 000000000..0f9299fe5
--- /dev/null
+++ b/arch/mips/cobalt/buttons.c
@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Cobalt buttons platform device.
+ *
+ *  Copyright (C) 2007  Yoichi Yuasa <yuasa@linux-mips.org>
+ */
+
+#include <linux/platform_device.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+
+static struct resource cobalt_buttons_resource __initdata = {
+	.start	= 0x1d000000,
+	.end	= 0x1d000003,
+	.flags	= IORESOURCE_MEM,
+};
+
+static __init int cobalt_add_buttons(void)
+{
+	struct platform_device *pd;
+	int error;
+
+	pd = platform_device_alloc("Cobalt buttons", -1);
+	if (!pd)
+		return -ENOMEM;
+
+	error = platform_device_add_resources(pd, &cobalt_buttons_resource, 1);
+	if (error)
+		goto err_free_device;
+
+	error = platform_device_add(pd);
+	if (error)
+		goto err_free_device;
+
+	return 0;
+
+ err_free_device:
+	platform_device_put(pd);
+	return error;
+}
+device_initcall(cobalt_add_buttons);