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, 96 insertions, 0 deletions

diff --git a/drivers/nvmem/sec-qfprom.c b/drivers/nvmem/sec-qfprom.c
new file mode 100644
index 000000000..51d21e65a
--- /dev/null
+++ b/drivers/nvmem/sec-qfprom.c
@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2023, Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+
+#include <linux/firmware/qcom/qcom_scm.h>
+#include <linux/nvmem-provider.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+
+/**
+ * struct sec_qfprom - structure holding secure qfprom attributes
+ *
+ * @base: starting physical address for secure qfprom corrected address space.
+ * @dev: qfprom device structure.
+ */
+struct sec_qfprom {
+	phys_addr_t base;
+	struct device *dev;
+};
+
+static int sec_qfprom_reg_read(void *context, unsigned int reg, void *_val, size_t bytes)
+{
+	struct sec_qfprom *priv = context;
+	unsigned int i;
+	u8 *val = _val;
+	u32 read_val;
+	u8 *tmp;
+
+	for (i = 0; i < bytes; i++, reg++) {
+		if (i == 0 || reg % 4 == 0) {
+			if (qcom_scm_io_readl(priv->base + (reg & ~3), &read_val)) {
+				dev_err(priv->dev, "Couldn't access fuse register\n");
+				return -EINVAL;
+			}
+			tmp = (u8 *)&read_val;
+		}
+
+		val[i] = tmp[reg & 3];
+	}
+
+	return 0;
+}
+
+static int sec_qfprom_probe(struct platform_device *pdev)
+{
+	struct nvmem_config econfig = {
+		.name = "sec-qfprom",
+		.add_legacy_fixed_of_cells = true,
+		.stride = 1,
+		.word_size = 1,
+		.id = NVMEM_DEVID_AUTO,
+		.reg_read = sec_qfprom_reg_read,
+	};
+	struct device *dev = &pdev->dev;
+	struct nvmem_device *nvmem;
+	struct sec_qfprom *priv;
+	struct resource *res;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -EINVAL;
+
+	priv->base = res->start;
+
+	econfig.size = resource_size(res);
+	econfig.dev = dev;
+	econfig.priv = priv;
+
+	priv->dev = dev;
+
+	nvmem = devm_nvmem_register(dev, &econfig);
+
+	return PTR_ERR_OR_ZERO(nvmem);
+}
+
+static const struct of_device_id sec_qfprom_of_match[] = {
+	{ .compatible = "qcom,sec-qfprom" },
+	{/* sentinel */},
+};
+MODULE_DEVICE_TABLE(of, sec_qfprom_of_match);
+
+static struct platform_driver qfprom_driver = {
+	.probe = sec_qfprom_probe,
+	.driver = {
+		.name = "qcom_sec_qfprom",
+		.of_match_table = sec_qfprom_of_match,
+	},
+};
+module_platform_driver(qfprom_driver);
+MODULE_DESCRIPTION("Qualcomm Secure QFPROM driver");
+MODULE_LICENSE("GPL");