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, 67 insertions, 0 deletions

diff --git a/drivers/nvmem/an8855-efuse.c b/drivers/nvmem/an8855-efuse.c
new file mode 100644
index 000000000..ed0840f79
--- /dev/null
+++ b/drivers/nvmem/an8855-efuse.c
@@ -0,0 +1,67 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  Airoha AN8855 Switch EFUSE Driver
+ */
+
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#define AN8855_EFUSE_CELL		50
+
+#define AN8855_EFUSE_DATA0		0x1000a500
+#define   AN8855_EFUSE_R50O		GENMASK(30, 24)
+
+static int an8855_efuse_read(void *context, unsigned int offset,
+			     void *val, size_t bytes)
+{
+	struct regmap *regmap = context;
+
+	return regmap_bulk_read(regmap, AN8855_EFUSE_DATA0 + offset,
+				val, bytes / sizeof(u32));
+}
+
+static int an8855_efuse_probe(struct platform_device *pdev)
+{
+	struct nvmem_config an8855_nvmem_config = {
+		.name = "an8855-efuse",
+		.size = AN8855_EFUSE_CELL * sizeof(u32),
+		.stride = sizeof(u32),
+		.word_size = sizeof(u32),
+		.reg_read = an8855_efuse_read,
+	};
+	struct device *dev = &pdev->dev;
+	struct nvmem_device *nvmem;
+	struct regmap *regmap;
+
+	/* Assign NVMEM priv to MFD regmap */
+	regmap = dev_get_regmap(dev->parent, NULL);
+	if (!regmap)
+		return -ENOENT;
+
+	an8855_nvmem_config.priv = regmap;
+	an8855_nvmem_config.dev = dev;
+	nvmem = devm_nvmem_register(dev, &an8855_nvmem_config);
+
+	return PTR_ERR_OR_ZERO(nvmem);
+}
+
+static const struct of_device_id an8855_efuse_of_match[] = {
+	{ .compatible = "airoha,an8855-efuse", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, an8855_efuse_of_match);
+
+static struct platform_driver an8855_efuse_driver = {
+	.probe = an8855_efuse_probe,
+	.driver = {
+		.name = "an8855-efuse",
+		.of_match_table = an8855_efuse_of_match,
+	},
+};
+module_platform_driver(an8855_efuse_driver);
+
+MODULE_AUTHOR("Christian Marangi <ansuelsmth@gmail.com>");
+MODULE_DESCRIPTION("Driver for AN8855 Switch EFUSE");
+MODULE_LICENSE("GPL");