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/arm/mach-s3c/dev-uart.c b/arch/arm/mach-s3c/dev-uart.c
new file mode 100644
index 000000000..3d1f7f2fd
--- /dev/null
+++ b/arch/arm/mach-s3c/dev-uart.c
@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+//	originally from arch/arm/plat-s3c24xx/devs.c
+//
+// Copyright (c) 2004 Simtec Electronics
+//	Ben Dooks <ben@simtec.co.uk>
+//
+// Base S3C24XX platform device definitions
+
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+
+#include "devs.h"
+
+/* uart devices */
+
+static struct platform_device s3c24xx_uart_device0 = {
+	.id		= 0,
+};
+
+static struct platform_device s3c24xx_uart_device1 = {
+	.id		= 1,
+};
+
+static struct platform_device s3c24xx_uart_device2 = {
+	.id		= 2,
+};
+
+static struct platform_device s3c24xx_uart_device3 = {
+	.id		= 3,
+};
+
+struct platform_device *s3c24xx_uart_src[4] = {
+	&s3c24xx_uart_device0,
+	&s3c24xx_uart_device1,
+	&s3c24xx_uart_device2,
+	&s3c24xx_uart_device3,
+};
+
+struct platform_device *s3c24xx_uart_devs[4] = {
+};