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, 69 insertions, 0 deletions

diff --git a/arch/arm/mach-omap2/omap-hotplug.c b/arch/arm/mach-omap2/omap-hotplug.c
new file mode 100644
index 000000000..8343fcf4f
--- /dev/null
+++ b/arch/arm/mach-omap2/omap-hotplug.c
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * OMAP4 SMP cpu-hotplug support
+ *
+ * Copyright (C) 2010 Texas Instruments, Inc.
+ * Author:
+ *      Santosh Shilimkar <santosh.shilimkar@ti.com>
+ *
+ * Platform file needed for the OMAP4 SMP. This file is based on arm
+ * realview smp platform.
+ * Copyright (c) 2002 ARM Limited.
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/smp.h>
+#include <linux/io.h>
+
+#include "omap-wakeupgen.h"
+#include "common.h"
+#include "powerdomain.h"
+
+/*
+ * platform-specific code to shutdown a CPU
+ * Called with IRQs disabled
+ */
+void omap4_cpu_die(unsigned int cpu)
+{
+	unsigned int boot_cpu = 0;
+	void __iomem *base = omap_get_wakeupgen_base();
+
+	/*
+	 * we're ready for shutdown now, so do it
+	 */
+	if (omap_secure_apis_support()) {
+		if (omap_modify_auxcoreboot0(0x0, 0x200) != 0x0)
+			pr_err("Secure clear status failed\n");
+	} else {
+		writel_relaxed(0, base + OMAP_AUX_CORE_BOOT_0);
+	}
+
+
+	for (;;) {
+		/*
+		 * Enter into low power state
+		 */
+		omap4_hotplug_cpu(cpu, PWRDM_POWER_OFF);
+
+		if (omap_secure_apis_support())
+			boot_cpu = omap_read_auxcoreboot0() >> 9;
+		else
+			boot_cpu =
+				readl_relaxed(base + OMAP_AUX_CORE_BOOT_0) >> 5;
+
+		if (boot_cpu == smp_processor_id()) {
+			/*
+			 * OK, proper wakeup, we're done
+			 */
+			break;
+		}
+		pr_debug("CPU%u: spurious wakeup call\n", cpu);
+	}
+}
+
+/* Needed by kexec and platform_can_cpu_hotplug() */
+int omap4_cpu_kill(unsigned int cpu)
+{
+	return 1;
+}