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, 126 insertions, 0 deletions

diff --git a/drivers/media/i2c/cs3308.c b/drivers/media/i2c/cs3308.c
new file mode 100644
index 000000000..ad37aeecf
--- /dev/null
+++ b/drivers/media/i2c/cs3308.c
@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Cirrus Logic cs3308 8-Channel Analog Volume Control
+ *
+ * Copyright (C) 2010 Devin Heitmueller <dheitmueller@kernellabs.com>
+ * Copyright (C) 2012 Steven Toth <stoth@kernellabs.com>
+ *
+ * Derived from cs5345.c Copyright (C) 2007 Hans Verkuil
+ */
+
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/i2c.h>
+#include <linux/slab.h>
+#include <linux/videodev2.h>
+#include <media/v4l2-device.h>
+
+MODULE_DESCRIPTION("i2c device driver for cs3308 8-channel volume control");
+MODULE_AUTHOR("Devin Heitmueller");
+MODULE_LICENSE("GPL");
+
+static inline int cs3308_write(struct v4l2_subdev *sd, u8 reg, u8 value)
+{
+	struct i2c_client *client = v4l2_get_subdevdata(sd);
+
+	return i2c_smbus_write_byte_data(client, reg, value);
+}
+
+static inline int cs3308_read(struct v4l2_subdev *sd, u8 reg)
+{
+	struct i2c_client *client = v4l2_get_subdevdata(sd);
+
+	return i2c_smbus_read_byte_data(client, reg);
+}
+
+#ifdef CONFIG_VIDEO_ADV_DEBUG
+static int cs3308_g_register(struct v4l2_subdev *sd, struct v4l2_dbg_register *reg)
+{
+	reg->val = cs3308_read(sd, reg->reg & 0xffff);
+	reg->size = 1;
+	return 0;
+}
+
+static int cs3308_s_register(struct v4l2_subdev *sd, const struct v4l2_dbg_register *reg)
+{
+	cs3308_write(sd, reg->reg & 0xffff, reg->val & 0xff);
+	return 0;
+}
+#endif
+
+/* ----------------------------------------------------------------------- */
+
+static const struct v4l2_subdev_core_ops cs3308_core_ops = {
+#ifdef CONFIG_VIDEO_ADV_DEBUG
+	.g_register = cs3308_g_register,
+	.s_register = cs3308_s_register,
+#endif
+};
+
+static const struct v4l2_subdev_ops cs3308_ops = {
+	.core = &cs3308_core_ops,
+};
+
+/* ----------------------------------------------------------------------- */
+
+static int cs3308_probe(struct i2c_client *client)
+{
+	struct v4l2_subdev *sd;
+	unsigned i;
+
+	/* Check if the adapter supports the needed features */
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_BYTE_DATA))
+		return -EIO;
+
+	if ((i2c_smbus_read_byte_data(client, 0x1c) & 0xf0) != 0xe0)
+		return -ENODEV;
+
+	v4l_info(client, "chip found @ 0x%x (%s)\n",
+		 client->addr << 1, client->adapter->name);
+
+	sd = kzalloc_obj(struct v4l2_subdev);
+	if (sd == NULL)
+		return -ENOMEM;
+
+	v4l2_i2c_subdev_init(sd, client, &cs3308_ops);
+
+	/* Set some reasonable defaults */
+	cs3308_write(sd, 0x0d, 0x00); /* Power up all channels */
+	cs3308_write(sd, 0x0e, 0x00); /* Master Power */
+	cs3308_write(sd, 0x0b, 0x00); /* Device Configuration */
+	/* Set volume for each channel */
+	for (i = 1; i <= 8; i++)
+		cs3308_write(sd, i, 0xd2);
+	cs3308_write(sd, 0x0a, 0x00); /* Unmute all channels */
+	return 0;
+}
+
+/* ----------------------------------------------------------------------- */
+
+static void cs3308_remove(struct i2c_client *client)
+{
+	struct v4l2_subdev *sd = i2c_get_clientdata(client);
+
+	v4l2_device_unregister_subdev(sd);
+	kfree(sd);
+}
+
+/* ----------------------------------------------------------------------- */
+
+static const struct i2c_device_id cs3308_id[] = {
+	{ .name = "cs3308" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, cs3308_id);
+
+static struct i2c_driver cs3308_driver = {
+	.driver = {
+		.name   = "cs3308",
+	},
+	.probe          = cs3308_probe,
+	.remove         = cs3308_remove,
+	.id_table       = cs3308_id,
+};
+
+module_i2c_driver(cs3308_driver);