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, 91 insertions, 0 deletions

diff --git a/drivers/hid/hid-vrc2.c b/drivers/hid/hid-vrc2.c
new file mode 100644
index 000000000..7dc41e92f
--- /dev/null
+++ b/drivers/hid/hid-vrc2.c
@@ -0,0 +1,91 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * HID driver for VRC-2 2-axis Car controller
+ *
+ * Copyright (C) 2022 Marcus Folkesson <marcus.folkesson@gmail.com>
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+/*
+ * VID/PID are probably "borrowed", so keep them locally and
+ * do not populate hid-ids.h with those.
+ */
+#define USB_VENDOR_ID_VRC2	(0x07c0)
+#define USB_DEVICE_ID_VRC2	(0x1125)
+
+static const __u8 vrc2_rdesc_fixed[] = {
+	0x05, 0x01,        // Usage Page (Generic Desktop Ctrls)
+	0x09, 0x04,        // Usage (Joystick)
+	0xA1, 0x01,        // Collection (Application)
+	0x09, 0x01,        //   Usage (Pointer)
+	0xA1, 0x00,        //   Collection (Physical)
+	0x09, 0x30,        //     Usage (X)
+	0x09, 0x31,        //     Usage (Y)
+	0x15, 0x00,        //     Logical Minimum (0)
+	0x26, 0xFF, 0x07,  //     Logical Maximum (2047)
+	0x35, 0x00,        //     Physical Minimum (0)
+	0x46, 0xFF, 0x00,  //     Physical Maximum (255)
+	0x75, 0x10,        //     Report Size (16)
+	0x95, 0x02,        //     Report Count (2)
+	0x81, 0x02,        //     Input (Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position)
+	0xC0,              //   End Collection
+	0x75, 0x08,        //   Report Size (8)
+	0x95, 0x03,        //   Report Count (3)
+	0x81, 0x03,        //   Input (Cnst,Var,Abs)
+	0xC0,              // End Collection
+};
+
+static const __u8 *vrc2_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+				     unsigned int *rsize)
+{
+	hid_info(hdev, "fixing up VRC-2 report descriptor\n");
+	*rsize = sizeof(vrc2_rdesc_fixed);
+	return vrc2_rdesc_fixed;
+}
+
+static int vrc2_probe(struct hid_device *hdev, const struct hid_device_id *id)
+{
+	int ret;
+
+	/*
+	 * The device gives us 2 separate USB endpoints.
+	 * One of those (the one with report descriptor size of 23) is just bogus so ignore it
+	 */
+	if (hdev->dev_rsize == 23)
+		return -ENODEV;
+
+	ret = hid_parse(hdev);
+	if (ret) {
+		hid_err(hdev, "parse failed\n");
+		return ret;
+	}
+
+	ret = hid_hw_start(hdev, HID_CONNECT_DEFAULT);
+	if (ret) {
+		hid_err(hdev, "hw start failed\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct hid_device_id vrc2_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_VRC2, USB_DEVICE_ID_VRC2) },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(hid, vrc2_devices);
+
+static struct hid_driver vrc2_driver = {
+	.name = "vrc2",
+	.id_table = vrc2_devices,
+	.report_fixup = vrc2_report_fixup,
+	.probe = vrc2_probe,
+};
+module_hid_driver(vrc2_driver);
+
+MODULE_AUTHOR("Marcus Folkesson <marcus.folkesson@gmail.com>");
+MODULE_DESCRIPTION("HID driver for VRC-2 2-axis Car controller");
+MODULE_LICENSE("GPL");