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, 81 insertions, 0 deletions

diff --git a/drivers/nvmem/apple-efuses.c b/drivers/nvmem/apple-efuses.c
new file mode 100644
index 000000000..9913e77b8
--- /dev/null
+++ b/drivers/nvmem/apple-efuses.c
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Apple SoC eFuse driver
+ *
+ * Copyright (C) The Asahi Linux Contributors
+ */
+
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/platform_device.h>
+
+struct apple_efuses_priv {
+	void __iomem *fuses;
+};
+
+static int apple_efuses_read(void *context, unsigned int offset, void *val,
+			     size_t bytes)
+{
+	struct apple_efuses_priv *priv = context;
+	u32 *dst = val;
+
+	while (bytes >= sizeof(u32)) {
+		*dst++ = readl_relaxed(priv->fuses + offset);
+		bytes -= sizeof(u32);
+		offset += sizeof(u32);
+	}
+
+	return 0;
+}
+
+static int apple_efuses_probe(struct platform_device *pdev)
+{
+	struct apple_efuses_priv *priv;
+	struct resource *res;
+	struct nvmem_config config = {
+		.dev = &pdev->dev,
+		.add_legacy_fixed_of_cells = true,
+		.read_only = true,
+		.reg_read = apple_efuses_read,
+		.stride = sizeof(u32),
+		.word_size = sizeof(u32),
+		.name = "apple_efuses_nvmem",
+		.id = NVMEM_DEVID_AUTO,
+		.root_only = true,
+	};
+
+	priv = devm_kzalloc(config.dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->fuses = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
+	if (IS_ERR(priv->fuses))
+		return PTR_ERR(priv->fuses);
+
+	config.priv = priv;
+	config.size = resource_size(res);
+
+	return PTR_ERR_OR_ZERO(devm_nvmem_register(config.dev, &config));
+}
+
+static const struct of_device_id apple_efuses_of_match[] = {
+	{ .compatible = "apple,efuses", },
+	{}
+};
+
+MODULE_DEVICE_TABLE(of, apple_efuses_of_match);
+
+static struct platform_driver apple_efuses_driver = {
+	.driver = {
+		.name = "apple_efuses",
+		.of_match_table = apple_efuses_of_match,
+	},
+	.probe = apple_efuses_probe,
+};
+
+module_platform_driver(apple_efuses_driver);
+
+MODULE_AUTHOR("Sven Peter <sven@svenpeter.dev>");
+MODULE_DESCRIPTION("Apple SoC eFuse driver");
+MODULE_LICENSE("GPL");