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, 107 insertions, 0 deletions

diff --git a/drivers/clk/visconti/reset.c b/drivers/clk/visconti/reset.c
new file mode 100644
index 000000000..e3c3d7804
--- /dev/null
+++ b/drivers/clk/visconti/reset.c
@@ -0,0 +1,107 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Toshiba Visconti ARM SoC reset controller
+ *
+ * Copyright (c) 2021 TOSHIBA CORPORATION
+ * Copyright (c) 2021 Toshiba Electronic Devices & Storage Corporation
+ *
+ * Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>
+ */
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/mfd/syscon.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+#include "reset.h"
+
+static inline struct visconti_reset *to_visconti_reset(struct reset_controller_dev *rcdev)
+{
+	return container_of(rcdev, struct visconti_reset, rcdev);
+}
+
+static int visconti_reset_assert(struct reset_controller_dev *rcdev, unsigned long id)
+{
+	struct visconti_reset *reset = to_visconti_reset(rcdev);
+	const struct visconti_reset_data *data = &reset->resets[id];
+	u32 rst = BIT(data->rs_idx);
+	unsigned long flags;
+	int ret;
+
+	spin_lock_irqsave(reset->lock, flags);
+	ret = regmap_update_bits(reset->regmap, data->rson_offset, rst, rst);
+	spin_unlock_irqrestore(reset->lock, flags);
+
+	return ret;
+}
+
+static int visconti_reset_deassert(struct reset_controller_dev *rcdev, unsigned long id)
+{
+	struct visconti_reset *reset = to_visconti_reset(rcdev);
+	const struct visconti_reset_data *data = &reset->resets[id];
+	u32 rst = BIT(data->rs_idx);
+	unsigned long flags;
+	int ret;
+
+	spin_lock_irqsave(reset->lock, flags);
+	ret = regmap_update_bits(reset->regmap, data->rsoff_offset, rst, rst);
+	spin_unlock_irqrestore(reset->lock, flags);
+
+	return ret;
+}
+
+static int visconti_reset_reset(struct reset_controller_dev *rcdev, unsigned long id)
+{
+	visconti_reset_assert(rcdev, id);
+	udelay(1);
+	visconti_reset_deassert(rcdev, id);
+
+	return 0;
+}
+
+static int visconti_reset_status(struct reset_controller_dev *rcdev, unsigned long id)
+{
+	struct visconti_reset *reset = to_visconti_reset(rcdev);
+	const struct visconti_reset_data *data = &reset->resets[id];
+	unsigned long flags;
+	u32 reg;
+	int ret;
+
+	spin_lock_irqsave(reset->lock, flags);
+	ret = regmap_read(reset->regmap, data->rson_offset, &reg);
+	spin_unlock_irqrestore(reset->lock, flags);
+	if (ret)
+		return ret;
+
+	return !(reg & data->rs_idx);
+}
+
+const struct reset_control_ops visconti_reset_ops = {
+	.assert		= visconti_reset_assert,
+	.deassert	= visconti_reset_deassert,
+	.reset		= visconti_reset_reset,
+	.status		= visconti_reset_status,
+};
+
+int visconti_register_reset_controller(struct device *dev,
+				       struct regmap *regmap,
+				       const struct visconti_reset_data *resets,
+				       unsigned int num_resets,
+				       const struct reset_control_ops *reset_ops,
+				       spinlock_t *lock)
+{
+	struct visconti_reset *reset;
+
+	reset = devm_kzalloc(dev, sizeof(*reset), GFP_KERNEL);
+	if (!reset)
+		return -ENOMEM;
+
+	reset->regmap = regmap;
+	reset->resets = resets;
+	reset->rcdev.ops = reset_ops;
+	reset->rcdev.nr_resets = num_resets;
+	reset->rcdev.of_node = dev->of_node;
+	reset->lock = lock;
+
+	return devm_reset_controller_register(dev, &reset->rcdev);
+}