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, 108 insertions, 0 deletions

diff --git a/drivers/nvmem/layerscape-sfp.c b/drivers/nvmem/layerscape-sfp.c
new file mode 100644
index 000000000..c1521afd5
--- /dev/null
+++ b/drivers/nvmem/layerscape-sfp.c
@@ -0,0 +1,108 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Layerscape SFP driver
+ *
+ * Copyright (c) 2022 Michael Walle <michael@walle.cc>
+ *
+ */
+
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+
+#define LAYERSCAPE_SFP_OTP_OFFSET	0x0200
+
+struct layerscape_sfp_priv {
+	struct regmap *regmap;
+};
+
+struct layerscape_sfp_data {
+	int size;
+	enum regmap_endian endian;
+};
+
+static int layerscape_sfp_read(void *context, unsigned int offset, void *val,
+			       size_t bytes)
+{
+	struct layerscape_sfp_priv *priv = context;
+
+	return regmap_bulk_read(priv->regmap,
+				LAYERSCAPE_SFP_OTP_OFFSET + offset, val,
+				bytes / 4);
+}
+
+static struct nvmem_config layerscape_sfp_nvmem_config = {
+	.name = "fsl-sfp",
+	.reg_read = layerscape_sfp_read,
+	.word_size = 4,
+	.stride = 4,
+};
+
+static int layerscape_sfp_probe(struct platform_device *pdev)
+{
+	const struct layerscape_sfp_data *data;
+	struct layerscape_sfp_priv *priv;
+	struct nvmem_device *nvmem;
+	struct regmap_config config = { 0 };
+	void __iomem *base;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(base))
+		return PTR_ERR(base);
+
+	data = device_get_match_data(&pdev->dev);
+	config.reg_bits = 32;
+	config.reg_stride = 4;
+	config.val_bits = 32;
+	config.val_format_endian = data->endian;
+	config.max_register = LAYERSCAPE_SFP_OTP_OFFSET + data->size - 4;
+	priv->regmap = devm_regmap_init_mmio(&pdev->dev, base, &config);
+	if (IS_ERR(priv->regmap))
+		return PTR_ERR(priv->regmap);
+
+	layerscape_sfp_nvmem_config.size = data->size;
+	layerscape_sfp_nvmem_config.dev = &pdev->dev;
+	layerscape_sfp_nvmem_config.priv = priv;
+
+	nvmem = devm_nvmem_register(&pdev->dev, &layerscape_sfp_nvmem_config);
+
+	return PTR_ERR_OR_ZERO(nvmem);
+}
+
+static const struct layerscape_sfp_data ls1021a_data = {
+	.size = 0x88,
+	.endian = REGMAP_ENDIAN_BIG,
+};
+
+static const struct layerscape_sfp_data ls1028a_data = {
+	.size = 0x88,
+	.endian = REGMAP_ENDIAN_LITTLE,
+};
+
+static const struct of_device_id layerscape_sfp_dt_ids[] = {
+	{ .compatible = "fsl,ls1021a-sfp", .data = &ls1021a_data },
+	{ .compatible = "fsl,ls1028a-sfp", .data = &ls1028a_data },
+	{},
+};
+MODULE_DEVICE_TABLE(of, layerscape_sfp_dt_ids);
+
+static struct platform_driver layerscape_sfp_driver = {
+	.probe	= layerscape_sfp_probe,
+	.driver = {
+		.name	= "layerscape_sfp",
+		.of_match_table = layerscape_sfp_dt_ids,
+	},
+};
+module_platform_driver(layerscape_sfp_driver);
+
+MODULE_AUTHOR("Michael Walle <michael@walle.cc>");
+MODULE_DESCRIPTION("Layerscape Security Fuse Processor driver");
+MODULE_LICENSE("GPL");