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, 112 insertions, 0 deletions

diff --git a/drivers/hid/hid-pxrc.c b/drivers/hid/hid-pxrc.c
new file mode 100644
index 000000000..71fe0c06d
--- /dev/null
+++ b/drivers/hid/hid-pxrc.c
@@ -0,0 +1,112 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * HID driver for PhoenixRC 8-axis flight controller
+ *
+ * Copyright (C) 2022 Marcus Folkesson <marcus.folkesson@gmail.com>
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+struct pxrc_priv {
+	u8 slider;
+	u8 dial;
+	bool alternate;
+};
+
+static const __u8 pxrc_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, 0x36,        //     Usage (Slider)
+	0x09, 0x31,        //     Usage (Y)
+	0x09, 0x32,        //     Usage (Z)
+	0x09, 0x33,        //     Usage (Rx)
+	0x09, 0x34,        //     Usage (Ry)
+	0x09, 0x35,        //     Usage (Rz)
+	0x09, 0x37,        //     Usage (Dial)
+	0x15, 0x00,        //     Logical Minimum (0)
+	0x26, 0xFF, 0x00,  //     Logical Maximum (255)
+	0x35, 0x00,        //     Physical Minimum (0)
+	0x46, 0xFF, 0x00,  //     Physical Maximum (255)
+	0x75, 0x08,        //     Report Size (8)
+	0x95, 0x08,        //     Report Count (8)
+	0x81, 0x02,        //     Input (Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position)
+	0xC0,              //   End Collection
+	0xC0,              // End Collection
+};
+
+static const __u8 *pxrc_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+				     unsigned int *rsize)
+{
+	hid_info(hdev, "fixing up PXRC report descriptor\n");
+	*rsize = sizeof(pxrc_rdesc_fixed);
+	return pxrc_rdesc_fixed;
+}
+
+static int pxrc_raw_event(struct hid_device *hdev, struct hid_report *report,
+	 u8 *data, int size)
+{
+	struct pxrc_priv *priv = hid_get_drvdata(hdev);
+
+	if (priv->alternate)
+		priv->slider = data[7];
+	else
+		priv->dial = data[7];
+
+	data[1] = priv->slider;
+	data[7] = priv->dial;
+
+	priv->alternate = !priv->alternate;
+	return 0;
+}
+
+static int pxrc_probe(struct hid_device *hdev, const struct hid_device_id *id)
+{
+	int ret;
+	struct pxrc_priv *priv;
+
+	priv = devm_kzalloc(&hdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+	hid_set_drvdata(hdev, priv);
+
+	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 pxrc_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_MULTIPLE_1781, USB_DEVICE_ID_PHOENIXRC) },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(hid, pxrc_devices);
+
+static struct hid_driver pxrc_driver = {
+	.name = "hid-pxrc",
+	.id_table = pxrc_devices,
+	.report_fixup = pxrc_report_fixup,
+	.probe = pxrc_probe,
+	.raw_event = pxrc_raw_event,
+};
+module_hid_driver(pxrc_driver);
+
+MODULE_AUTHOR("Marcus Folkesson <marcus.folkesson@gmail.com>");
+MODULE_DESCRIPTION("HID driver for PXRC 8-axis flight controller");
+MODULE_LICENSE("GPL");