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, 43 insertions, 0 deletions

diff --git a/arch/mips/ralink/reset.c b/arch/mips/ralink/reset.c
new file mode 100644
index 000000000..4875637ef
--- /dev/null
+++ b/arch/mips/ralink/reset.c
@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *
+ * Copyright (C) 2008-2009 Gabor Juhos <juhosg@openwrt.org>
+ * Copyright (C) 2008 Imre Kaloz <kaloz@openwrt.org>
+ * Copyright (C) 2013 John Crispin <john@phrozen.org>
+ */
+
+#include <linux/pm.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/delay.h>
+
+#include <asm/reboot.h>
+
+#include <asm/mach-ralink/ralink_regs.h>
+
+/* Reset Control */
+#define SYSC_REG_RESET_CTRL	0x034
+
+#define RSTCTL_RESET_PCI	BIT(26)
+#define RSTCTL_RESET_SYSTEM	BIT(0)
+
+static void ralink_restart(char *command)
+{
+	if (IS_ENABLED(CONFIG_PCI)) {
+		rt_sysc_m32(0, RSTCTL_RESET_PCI, SYSC_REG_RESET_CTRL);
+		mdelay(50);
+	}
+
+	local_irq_disable();
+	rt_sysc_w32(RSTCTL_RESET_SYSTEM, SYSC_REG_RESET_CTRL);
+	unreachable();
+}
+
+static int __init mips_reboot_setup(void)
+{
+	_machine_restart = ralink_restart;
+
+	return 0;
+}
+
+arch_initcall(mips_reboot_setup);