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, 169 insertions, 0 deletions

diff --git a/drivers/nvmem/layouts/sl28vpd.c b/drivers/nvmem/layouts/sl28vpd.c
new file mode 100644
index 000000000..e93b020b0
--- /dev/null
+++ b/drivers/nvmem/layouts/sl28vpd.c
@@ -0,0 +1,169 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/crc8.h>
+#include <linux/etherdevice.h>
+#include <linux/nvmem-consumer.h>
+#include <linux/nvmem-provider.h>
+#include <linux/of.h>
+#include <uapi/linux/if_ether.h>
+
+#define SL28VPD_MAGIC 'V'
+
+struct sl28vpd_header {
+	u8 magic;
+	u8 version;
+} __packed;
+
+struct sl28vpd_v1 {
+	struct sl28vpd_header header;
+	char serial_number[15];
+	u8 base_mac_address[ETH_ALEN];
+	u8 crc8;
+} __packed;
+
+static int sl28vpd_mac_address_pp(void *priv, const char *id, int index,
+				  unsigned int offset, void *buf,
+				  size_t bytes)
+{
+	if (bytes != ETH_ALEN)
+		return -EINVAL;
+
+	if (index < 0)
+		return -EINVAL;
+
+	if (!is_valid_ether_addr(buf))
+		return -EINVAL;
+
+	eth_addr_add(buf, index);
+
+	return 0;
+}
+
+static const struct nvmem_cell_info sl28vpd_v1_entries[] = {
+	{
+		.name = "serial-number",
+		.offset = offsetof(struct sl28vpd_v1, serial_number),
+		.bytes = sizeof_field(struct sl28vpd_v1, serial_number),
+	},
+	{
+		.name = "base-mac-address",
+		.offset = offsetof(struct sl28vpd_v1, base_mac_address),
+		.bytes = sizeof_field(struct sl28vpd_v1, base_mac_address),
+		.read_post_process = sl28vpd_mac_address_pp,
+	},
+};
+
+static int sl28vpd_v1_check_crc(struct device *dev, struct nvmem_device *nvmem)
+{
+	struct sl28vpd_v1 data_v1;
+	u8 table[CRC8_TABLE_SIZE];
+	int ret;
+	u8 crc;
+
+	crc8_populate_msb(table, 0x07);
+
+	ret = nvmem_device_read(nvmem, 0, sizeof(data_v1), &data_v1);
+	if (ret < 0)
+		return ret;
+	else if (ret != sizeof(data_v1))
+		return -EIO;
+
+	crc = crc8(table, (void *)&data_v1, sizeof(data_v1) - 1, 0);
+
+	if (crc != data_v1.crc8) {
+		dev_err(dev,
+			"Checksum is invalid (got %02x, expected %02x).\n",
+			crc, data_v1.crc8);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int sl28vpd_add_cells(struct nvmem_layout *layout)
+{
+	struct nvmem_device *nvmem = layout->nvmem;
+	struct device *dev = &layout->dev;
+	const struct nvmem_cell_info *pinfo;
+	struct nvmem_cell_info info = {0};
+	struct device_node *layout_np;
+	struct sl28vpd_header hdr;
+	int ret, i;
+
+	/* check header */
+	ret = nvmem_device_read(nvmem, 0, sizeof(hdr), &hdr);
+	if (ret < 0)
+		return ret;
+	else if (ret != sizeof(hdr))
+		return -EIO;
+
+	if (hdr.magic != SL28VPD_MAGIC) {
+		dev_err(dev, "Invalid magic value (%02x)\n", hdr.magic);
+		return -EINVAL;
+	}
+
+	if (hdr.version != 1) {
+		dev_err(dev, "Version %d is unsupported.\n", hdr.version);
+		return -EINVAL;
+	}
+
+	ret = sl28vpd_v1_check_crc(dev, nvmem);
+	if (ret)
+		return ret;
+
+	layout_np = of_nvmem_layout_get_container(nvmem);
+	if (!layout_np)
+		return -ENOENT;
+
+	for (i = 0; i < ARRAY_SIZE(sl28vpd_v1_entries); i++) {
+		pinfo = &sl28vpd_v1_entries[i];
+
+		info.name = pinfo->name;
+		info.offset = pinfo->offset;
+		info.bytes = pinfo->bytes;
+		info.read_post_process = pinfo->read_post_process;
+		info.np = of_get_child_by_name(layout_np, pinfo->name);
+
+		ret = nvmem_add_one_cell(nvmem, &info);
+		if (ret) {
+			of_node_put(layout_np);
+			return ret;
+		}
+	}
+
+	of_node_put(layout_np);
+
+	return 0;
+}
+
+static int sl28vpd_probe(struct nvmem_layout *layout)
+{
+	layout->add_cells = sl28vpd_add_cells;
+
+	return nvmem_layout_register(layout);
+}
+
+static void sl28vpd_remove(struct nvmem_layout *layout)
+{
+	nvmem_layout_unregister(layout);
+}
+
+static const struct of_device_id sl28vpd_of_match_table[] = {
+	{ .compatible = "kontron,sl28-vpd" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, sl28vpd_of_match_table);
+
+static struct nvmem_layout_driver sl28vpd_layout = {
+	.driver = {
+		.name = "kontron-sl28vpd-layout",
+		.of_match_table = sl28vpd_of_match_table,
+	},
+	.probe = sl28vpd_probe,
+	.remove = sl28vpd_remove,
+};
+module_nvmem_layout_driver(sl28vpd_layout);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Michael Walle <michael@walle.cc>");
+MODULE_DESCRIPTION("NVMEM layout driver for the VPD of Kontron sl28 boards");