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, 157 insertions, 0 deletions

diff --git a/drivers/nvmem/snvs_lpgpr.c b/drivers/nvmem/snvs_lpgpr.c
new file mode 100644
index 000000000..89c271123
--- /dev/null
+++ b/drivers/nvmem/snvs_lpgpr.c
@@ -0,0 +1,157 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2015 Pengutronix, Steffen Trumtrar <kernel@pengutronix.de>
+ * Copyright (c) 2017 Pengutronix, Oleksij Rempel <kernel@pengutronix.de>
+ */
+
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#define IMX6Q_SNVS_HPLR		0x00
+#define IMX6Q_SNVS_LPLR		0x34
+#define IMX6Q_SNVS_LPGPR	0x68
+
+#define IMX7D_SNVS_HPLR		0x00
+#define IMX7D_SNVS_LPLR		0x34
+#define IMX7D_SNVS_LPGPR	0x90
+
+#define IMX_GPR_SL		BIT(5)
+#define IMX_GPR_HL		BIT(5)
+
+struct snvs_lpgpr_cfg {
+	int offset;
+	int offset_hplr;
+	int offset_lplr;
+	int size;
+};
+
+struct snvs_lpgpr_priv {
+	struct device_d			*dev;
+	struct regmap			*regmap;
+	struct nvmem_config		cfg;
+	const struct snvs_lpgpr_cfg	*dcfg;
+};
+
+static const struct snvs_lpgpr_cfg snvs_lpgpr_cfg_imx6q = {
+	.offset		= IMX6Q_SNVS_LPGPR,
+	.offset_hplr	= IMX6Q_SNVS_HPLR,
+	.offset_lplr	= IMX6Q_SNVS_LPLR,
+	.size		= 4,
+};
+
+static const struct snvs_lpgpr_cfg snvs_lpgpr_cfg_imx7d = {
+	.offset		= IMX7D_SNVS_LPGPR,
+	.offset_hplr	= IMX7D_SNVS_HPLR,
+	.offset_lplr	= IMX7D_SNVS_LPLR,
+	.size		= 16,
+};
+
+static int snvs_lpgpr_write(void *context, unsigned int offset, void *val,
+			    size_t bytes)
+{
+	struct snvs_lpgpr_priv *priv = context;
+	const struct snvs_lpgpr_cfg *dcfg = priv->dcfg;
+	unsigned int lock_reg;
+	int ret;
+
+	ret = regmap_read(priv->regmap, dcfg->offset_hplr, &lock_reg);
+	if (ret < 0)
+		return ret;
+
+	if (lock_reg & IMX_GPR_SL)
+		return -EPERM;
+
+	ret = regmap_read(priv->regmap, dcfg->offset_lplr, &lock_reg);
+	if (ret < 0)
+		return ret;
+
+	if (lock_reg & IMX_GPR_HL)
+		return -EPERM;
+
+	return regmap_bulk_write(priv->regmap, dcfg->offset + offset, val,
+				bytes / 4);
+}
+
+static int snvs_lpgpr_read(void *context, unsigned int offset, void *val,
+			   size_t bytes)
+{
+	struct snvs_lpgpr_priv *priv = context;
+	const struct snvs_lpgpr_cfg *dcfg = priv->dcfg;
+
+	return regmap_bulk_read(priv->regmap, dcfg->offset + offset,
+			       val, bytes / 4);
+}
+
+static int snvs_lpgpr_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *node = dev->of_node;
+	struct device_node *syscon_node;
+	struct snvs_lpgpr_priv *priv;
+	struct nvmem_config *cfg;
+	struct nvmem_device *nvmem;
+	const struct snvs_lpgpr_cfg *dcfg;
+
+	if (!node)
+		return -ENOENT;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	dcfg = of_device_get_match_data(dev);
+	if (!dcfg)
+		return -EINVAL;
+
+	syscon_node = of_get_parent(node);
+	if (!syscon_node)
+		return -ENODEV;
+
+	priv->regmap = syscon_node_to_regmap(syscon_node);
+	of_node_put(syscon_node);
+	if (IS_ERR(priv->regmap))
+		return PTR_ERR(priv->regmap);
+
+	priv->dcfg = dcfg;
+
+	cfg = &priv->cfg;
+	cfg->priv = priv;
+	cfg->name = dev_name(dev);
+	cfg->dev = dev;
+	cfg->stride = 4;
+	cfg->word_size = 4;
+	cfg->size = dcfg->size;
+	cfg->owner = THIS_MODULE;
+	cfg->reg_read  = snvs_lpgpr_read;
+	cfg->reg_write = snvs_lpgpr_write;
+
+	nvmem = devm_nvmem_register(dev, cfg);
+
+	return PTR_ERR_OR_ZERO(nvmem);
+}
+
+static const struct of_device_id snvs_lpgpr_dt_ids[] = {
+	{ .compatible = "fsl,imx6q-snvs-lpgpr", .data = &snvs_lpgpr_cfg_imx6q },
+	{ .compatible = "fsl,imx6ul-snvs-lpgpr",
+	  .data = &snvs_lpgpr_cfg_imx6q },
+	{ .compatible = "fsl,imx7d-snvs-lpgpr",	.data = &snvs_lpgpr_cfg_imx7d },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, snvs_lpgpr_dt_ids);
+
+static struct platform_driver snvs_lpgpr_driver = {
+	.probe	= snvs_lpgpr_probe,
+	.driver = {
+		.name	= "snvs_lpgpr",
+		.of_match_table = snvs_lpgpr_dt_ids,
+	},
+};
+module_platform_driver(snvs_lpgpr_driver);
+
+MODULE_AUTHOR("Oleksij Rempel <o.rempel@pengutronix.de>");
+MODULE_DESCRIPTION("Low Power General Purpose Register in i.MX6 and i.MX7 Secure Non-Volatile Storage");
+MODULE_LICENSE("GPL v2");