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, 90 insertions, 0 deletions

diff --git a/drivers/hid/hid-belkin.c b/drivers/hid/hid-belkin.c
new file mode 100644
index 000000000..84695115d
--- /dev/null
+++ b/drivers/hid/hid-belkin.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  HID driver for some belkin "special" devices
+ *
+ *  Copyright (c) 1999 Andreas Gal
+ *  Copyright (c) 2000-2005 Vojtech Pavlik <vojtech@suse.cz>
+ *  Copyright (c) 2005 Michael Haboustak <mike-@cinci.rr.com> for Concept2, Inc
+ *  Copyright (c) 2006-2007 Jiri Kosina
+ *  Copyright (c) 2008 Jiri Slaby
+ */
+
+/*
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+#define BELKIN_HIDDEV	0x01
+#define BELKIN_WKBD	0x02
+
+#define belkin_map_key_clear(c)	hid_map_usage_clear(hi, usage, bit, max, \
+					EV_KEY, (c))
+static int belkin_input_mapping(struct hid_device *hdev, struct hid_input *hi,
+		struct hid_field *field, struct hid_usage *usage,
+		unsigned long **bit, int *max)
+{
+	const struct hid_device_id *id = hid_get_drvdata(hdev);
+	unsigned long quirks = id->driver_data;
+
+	if ((usage->hid & HID_USAGE_PAGE) != HID_UP_CONSUMER ||
+			!(quirks & BELKIN_WKBD))
+		return 0;
+
+	switch (usage->hid & HID_USAGE) {
+	case 0x03a: belkin_map_key_clear(KEY_SOUND);		break;
+	case 0x03b: belkin_map_key_clear(KEY_CAMERA);		break;
+	case 0x03c: belkin_map_key_clear(KEY_DOCUMENTS);	break;
+	default:
+		return 0;
+	}
+	return 1;
+}
+
+static int belkin_probe(struct hid_device *hdev, const struct hid_device_id *id)
+{
+	unsigned long quirks = id->driver_data;
+	int ret;
+
+	hid_set_drvdata(hdev, (void *)id);
+
+	ret = hid_parse(hdev);
+	if (ret) {
+		hid_err(hdev, "parse failed\n");
+		goto err_free;
+	}
+
+	ret = hid_hw_start(hdev, HID_CONNECT_DEFAULT |
+		((quirks & BELKIN_HIDDEV) ? HID_CONNECT_HIDDEV_FORCE : 0));
+	if (ret) {
+		hid_err(hdev, "hw start failed\n");
+		goto err_free;
+	}
+
+	return 0;
+err_free:
+	return ret;
+}
+
+static const struct hid_device_id belkin_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_BELKIN, USB_DEVICE_ID_FLIP_KVM),
+		.driver_data = BELKIN_HIDDEV },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_LABTEC, USB_DEVICE_ID_LABTEC_WIRELESS_KEYBOARD),
+		.driver_data = BELKIN_WKBD },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, belkin_devices);
+
+static struct hid_driver belkin_driver = {
+	.name = "belkin",
+	.id_table = belkin_devices,
+	.input_mapping = belkin_input_mapping,
+	.probe = belkin_probe,
+};
+module_hid_driver(belkin_driver);
+
+MODULE_DESCRIPTION("HID driver for some belkin \"special\" devices");
+MODULE_LICENSE("GPL");