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, 99 insertions, 0 deletions

diff --git a/drivers/media/i2c/uda1342.c b/drivers/media/i2c/uda1342.c
new file mode 100644
index 000000000..437726788
--- /dev/null
+++ b/drivers/media/i2c/uda1342.c
@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2005-2006 Micronas USA Inc.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/i2c.h>
+#include <linux/videodev2.h>
+#include <media/v4l2-device.h>
+#include <media/i2c/uda1342.h>
+#include <linux/slab.h>
+
+static int write_reg(struct i2c_client *client, int reg, int value)
+{
+	/* UDA1342 wants MSB first, but SMBus sends LSB first */
+	i2c_smbus_write_word_data(client, reg, swab16(value));
+	return 0;
+}
+
+static int uda1342_s_routing(struct v4l2_subdev *sd,
+		u32 input, u32 output, u32 config)
+{
+	struct i2c_client *client = v4l2_get_subdevdata(sd);
+
+	switch (input) {
+	case UDA1342_IN1:
+		write_reg(client, 0x00, 0x1241); /* select input 1 */
+		break;
+	case UDA1342_IN2:
+		write_reg(client, 0x00, 0x1441); /* select input 2 */
+		break;
+	default:
+		v4l2_err(sd, "input %d not supported\n", input);
+		break;
+	}
+	return 0;
+}
+
+static const struct v4l2_subdev_audio_ops uda1342_audio_ops = {
+	.s_routing = uda1342_s_routing,
+};
+
+static const struct v4l2_subdev_ops uda1342_ops = {
+	.audio = &uda1342_audio_ops,
+};
+
+static int uda1342_probe(struct i2c_client *client)
+{
+	struct i2c_adapter *adapter = client->adapter;
+	struct v4l2_subdev *sd;
+
+	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WORD_DATA))
+		return -ENODEV;
+
+	dev_dbg(&client->dev, "initializing UDA1342 at address %d on %s\n",
+		client->addr, adapter->name);
+
+	sd = devm_kzalloc(&client->dev, sizeof(*sd), GFP_KERNEL);
+	if (sd == NULL)
+		return -ENOMEM;
+
+	v4l2_i2c_subdev_init(sd, client, &uda1342_ops);
+
+	write_reg(client, 0x00, 0x8000); /* reset registers */
+	write_reg(client, 0x00, 0x1241); /* select input 1 */
+
+	v4l_info(client, "chip found @ 0x%02x (%s)\n",
+			client->addr << 1, client->adapter->name);
+
+	return 0;
+}
+
+static void uda1342_remove(struct i2c_client *client)
+{
+	struct v4l2_subdev *sd = i2c_get_clientdata(client);
+
+	v4l2_device_unregister_subdev(sd);
+}
+
+static const struct i2c_device_id uda1342_id[] = {
+	{ .name = "uda1342" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, uda1342_id);
+
+static struct i2c_driver uda1342_driver = {
+	.driver = {
+		.name	= "uda1342",
+	},
+	.probe		= uda1342_probe,
+	.remove		= uda1342_remove,
+	.id_table	= uda1342_id,
+};
+
+module_i2c_driver(uda1342_driver);
+
+MODULE_DESCRIPTION("Philips UDA1342 audio codec driver");
+MODULE_LICENSE("GPL v2");