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, 38 insertions, 0 deletions

diff --git a/arch/m68k/coldfire/mcf8390.c b/arch/m68k/coldfire/mcf8390.c
new file mode 100644
index 000000000..23a6874a3
--- /dev/null
+++ b/arch/m68k/coldfire/mcf8390.c
@@ -0,0 +1,38 @@
+/*
+ * mcf8390.c  -- platform support for 8390 ethernet on many boards
+ *
+ * (C) Copyright 2012, Greg Ungerer <gerg@uclinux.org>
+ *
+ * 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.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/resource.h>
+#include <linux/platform_device.h>
+#include <asm/mcf8390.h>
+
+static struct resource mcf8390_resources[] = {
+	{
+		.start	= NE2000_ADDR,
+		.end	= NE2000_ADDR + NE2000_ADDRSIZE - 1,
+		.flags	= IORESOURCE_MEM,
+	},
+	{
+		.start	= NE2000_IRQ_VECTOR,
+		.end	= NE2000_IRQ_VECTOR,
+		.flags	= IORESOURCE_IRQ,
+	},
+};
+
+static int __init mcf8390_platform_init(void)
+{
+	platform_device_register_simple("mcf8390", -1, mcf8390_resources,
+		ARRAY_SIZE(mcf8390_resources));
+	return 0;
+}
+
+arch_initcall(mcf8390_platform_init);