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, 47 insertions, 0 deletions

diff --git a/arch/mips/cobalt/mtd.c b/arch/mips/cobalt/mtd.c
new file mode 100644
index 000000000..95f579d8c
--- /dev/null
+++ b/arch/mips/cobalt/mtd.c
@@ -0,0 +1,47 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Registration of Cobalt MTD device.
+ *
+ *  Copyright (C) 2006  Yoichi Yuasa <yuasa@linux-mips.org>
+ */
+#include <linux/init.h>
+#include <linux/platform_device.h>
+#include <linux/mtd/partitions.h>
+#include <linux/mtd/physmap.h>
+
+static struct mtd_partition cobalt_mtd_partitions[] = {
+	{
+		.name	= "firmware",
+		.offset = 0x0,
+		.size	= 0x80000,
+	},
+};
+
+static struct physmap_flash_data cobalt_flash_data = {
+	.width		= 1,
+	.nr_parts	= 1,
+	.parts		= cobalt_mtd_partitions,
+};
+
+static struct resource cobalt_mtd_resource = {
+	.start	= 0x1fc00000,
+	.end	= 0x1fc7ffff,
+	.flags	= IORESOURCE_MEM,
+};
+
+static struct platform_device cobalt_mtd = {
+	.name		= "physmap-flash",
+	.dev		= {
+		.platform_data	= &cobalt_flash_data,
+	},
+	.num_resources	= 1,
+	.resource	= &cobalt_mtd_resource,
+};
+
+static int __init cobalt_mtd_init(void)
+{
+	platform_device_register(&cobalt_mtd);
+
+	return 0;
+}
+device_initcall(cobalt_mtd_init);