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, 93 insertions, 0 deletions

diff --git a/drivers/media/i2c/ov7640.c b/drivers/media/i2c/ov7640.c
new file mode 100644
index 000000000..0fd90bc67
--- /dev/null
+++ b/drivers/media/i2c/ov7640.c
@@ -0,0 +1,93 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2005-2006 Micronas USA Inc.
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/videodev2.h>
+#include <media/v4l2-device.h>
+#include <linux/slab.h>
+
+MODULE_DESCRIPTION("OmniVision ov7640 sensor driver");
+MODULE_LICENSE("GPL v2");
+
+struct reg_val {
+	u8 reg;
+	u8 val;
+};
+
+static const struct reg_val regval_init[] = {
+	{0x12, 0x80},
+	{0x12, 0x54},
+	{0x14, 0x24},
+	{0x15, 0x01},
+	{0x28, 0x20},
+	{0x75, 0x82},
+};
+
+static int write_regs(struct i2c_client *client,
+		const struct reg_val *rv, int len)
+{
+	while (--len >= 0) {
+		if (i2c_smbus_write_byte_data(client, rv->reg, rv->val) < 0)
+			return -1;
+		rv++;
+	}
+	return 0;
+}
+
+/* ----------------------------------------------------------------------- */
+
+static const struct v4l2_subdev_ops ov7640_ops;
+
+static int ov7640_probe(struct i2c_client *client)
+{
+	struct i2c_adapter *adapter = client->adapter;
+	struct v4l2_subdev *sd;
+
+	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
+		return -ENODEV;
+
+	sd = devm_kzalloc(&client->dev, sizeof(*sd), GFP_KERNEL);
+	if (sd == NULL)
+		return -ENOMEM;
+	v4l2_i2c_subdev_init(sd, client, &ov7640_ops);
+
+	client->flags = I2C_CLIENT_SCCB;
+
+	v4l_info(client, "chip found @ 0x%02x (%s)\n",
+			client->addr << 1, client->adapter->name);
+
+	if (write_regs(client, regval_init, ARRAY_SIZE(regval_init)) < 0) {
+		v4l_err(client, "error initializing OV7640\n");
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+
+static void ov7640_remove(struct i2c_client *client)
+{
+	struct v4l2_subdev *sd = i2c_get_clientdata(client);
+
+	v4l2_device_unregister_subdev(sd);
+}
+
+static const struct i2c_device_id ov7640_id[] = {
+	{ .name = "ov7640" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, ov7640_id);
+
+static struct i2c_driver ov7640_driver = {
+	.driver = {
+		.name	= "ov7640",
+	},
+	.probe = ov7640_probe,
+	.remove = ov7640_remove,
+	.id_table = ov7640_id,
+};
+module_i2c_driver(ov7640_driver);