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, 74 insertions, 0 deletions

diff --git a/arch/arm/mach-tegra/hotplug.c b/arch/arm/mach-tegra/hotplug.c
new file mode 100644
index 000000000..5c907c2c0
--- /dev/null
+++ b/arch/arm/mach-tegra/hotplug.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  Copyright (C) 2002 ARM Ltd.
+ *  All Rights Reserved
+ *  Copyright (c) 2010, 2012-2013, NVIDIA Corporation. All rights reserved.
+ */
+
+#include <linux/clk/tegra.h>
+#include <linux/kernel.h>
+#include <linux/smp.h>
+
+#include <soc/tegra/common.h>
+#include <soc/tegra/fuse.h>
+
+#include <asm/smp_plat.h>
+
+#include "common.h"
+#include "sleep.h"
+
+static void (*tegra_hotplug_shutdown)(void);
+
+int tegra_cpu_kill(unsigned cpu)
+{
+	cpu = cpu_logical_map(cpu);
+
+	/* Clock gate the CPU */
+	tegra_wait_cpu_in_reset(cpu);
+	tegra_disable_cpu_clock(cpu);
+
+	return 1;
+}
+
+/*
+ * platform-specific code to shutdown a CPU
+ *
+ * Called with IRQs disabled
+ */
+void tegra_cpu_die(unsigned int cpu)
+{
+	if (!tegra_hotplug_shutdown) {
+		WARN(1, "hotplug is not yet initialized\n");
+		return;
+	}
+
+	/* Clean L1 data cache */
+	tegra_disable_clean_inv_dcache(TEGRA_FLUSH_CACHE_LOUIS);
+
+	/* Shut down the current CPU. */
+	tegra_hotplug_shutdown();
+
+	/* Should never return here. */
+	BUG();
+}
+
+static int __init tegra_hotplug_init(void)
+{
+	if (!IS_ENABLED(CONFIG_HOTPLUG_CPU))
+		return 0;
+
+	if (!soc_is_tegra())
+		return 0;
+
+	if (IS_ENABLED(CONFIG_ARCH_TEGRA_2x_SOC) && tegra_get_chip_id() == TEGRA20)
+		tegra_hotplug_shutdown = tegra20_hotplug_shutdown;
+	if (IS_ENABLED(CONFIG_ARCH_TEGRA_3x_SOC) && tegra_get_chip_id() == TEGRA30)
+		tegra_hotplug_shutdown = tegra30_hotplug_shutdown;
+	if (IS_ENABLED(CONFIG_ARCH_TEGRA_114_SOC) && tegra_get_chip_id() == TEGRA114)
+		tegra_hotplug_shutdown = tegra30_hotplug_shutdown;
+	if (IS_ENABLED(CONFIG_ARCH_TEGRA_124_SOC) && tegra_get_chip_id() == TEGRA124)
+		tegra_hotplug_shutdown = tegra30_hotplug_shutdown;
+
+	return 0;
+}
+pure_initcall(tegra_hotplug_init);