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/arch/mips/bcm63xx/dev-rng.c b/arch/mips/bcm63xx/dev-rng.c
new file mode 100644
index 000000000..f94151f7c
--- /dev/null
+++ b/arch/mips/bcm63xx/dev-rng.c
@@ -0,0 +1,40 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2011 Florian Fainelli <florian@openwrt.org>
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+#include <bcm63xx_cpu.h>
+
+static struct resource rng_resources[] = {
+	{
+		.start		= -1, /* filled at runtime */
+		.end		= -1, /* filled at runtime */
+		.flags		= IORESOURCE_MEM,
+	},
+};
+
+static struct platform_device bcm63xx_rng_device = {
+	.name		= "bcm63xx-rng",
+	.id		= -1,
+	.num_resources	= ARRAY_SIZE(rng_resources),
+	.resource	= rng_resources,
+};
+
+static int __init bcm63xx_rng_register(void)
+{
+	if (!BCMCPU_IS_6368())
+		return -ENODEV;
+
+	rng_resources[0].start = bcm63xx_regset_address(RSET_RNG);
+	rng_resources[0].end = rng_resources[0].start;
+	rng_resources[0].end += RSET_RNG_SIZE - 1;
+
+	return platform_device_register(&bcm63xx_rng_device);
+}
+arch_initcall(bcm63xx_rng_register);