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, 113 insertions, 0 deletions

diff --git a/drivers/hid/hid-gembird.c b/drivers/hid/hid-gembird.c
new file mode 100644
index 000000000..20a8de766
--- /dev/null
+++ b/drivers/hid/hid-gembird.c
@@ -0,0 +1,113 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  HID driver for Gembird Joypad, "PC Game Controller"
+ *
+ *  Copyright (c) 2015 Red Hat, Inc
+ *  Copyright (c) 2015 Benjamin Tissoires
+ */
+
+/*
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+#define GEMBIRD_START_FAULTY_RDESC	8
+
+static const __u8 gembird_jpd_faulty_rdesc[] = {
+	0x75, 0x08,			/*   Report Size (8)		*/
+	0x95, 0x05,			/*   Report Count (5)		*/
+	0x15, 0x00,			/*   Logical Minimum (0)	*/
+	0x26, 0xff, 0x00,		/*   Logical Maximum (255)	*/
+	0x35, 0x00,			/*   Physical Minimum (0)	*/
+	0x46, 0xff, 0x00,		/*   Physical Maximum (255)	*/
+	0x09, 0x30,			/*   Usage (X)			*/
+	0x09, 0x31,			/*   Usage (Y)			*/
+	0x09, 0x32,			/*   Usage (Z)			*/
+	0x09, 0x32,			/*   Usage (Z)			*/
+	0x09, 0x35,			/*   Usage (Rz)			*/
+	0x81, 0x02,			/*   Input (Data,Var,Abs)	*/
+};
+
+/*
+ * we fix the report descriptor by:
+ * - marking the first Z axis as constant (so it is ignored by HID)
+ * - assign the original second Z to Rx
+ * - assign the original Rz to Ry
+ */
+static const __u8 gembird_jpd_fixed_rdesc[] = {
+	0x75, 0x08,			/*   Report Size (8)		*/
+	0x95, 0x02,			/*   Report Count (2)		*/
+	0x15, 0x00,			/*   Logical Minimum (0)	*/
+	0x26, 0xff, 0x00,		/*   Logical Maximum (255)	*/
+	0x35, 0x00,			/*   Physical Minimum (0)	*/
+	0x46, 0xff, 0x00,		/*   Physical Maximum (255)	*/
+	0x09, 0x30,			/*   Usage (X)			*/
+	0x09, 0x31,			/*   Usage (Y)			*/
+	0x81, 0x02,			/*   Input (Data,Var,Abs)	*/
+	0x95, 0x01,			/*   Report Count (1)		*/
+	0x09, 0x32,			/*   Usage (Z)			*/
+	0x81, 0x01,			/*   Input (Cnst,Arr,Abs)	*/
+	0x95, 0x02,			/*   Report Count (2)		*/
+	0x09, 0x33,			/*   Usage (Rx)			*/
+	0x09, 0x34,			/*   Usage (Ry)			*/
+	0x81, 0x02,			/*   Input (Data,Var,Abs)	*/
+};
+
+static const __u8 *gembird_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+		unsigned int *rsize)
+{
+	__u8 *new_rdesc;
+	/* delta_size is > 0 */
+	size_t delta_size = sizeof(gembird_jpd_fixed_rdesc) -
+			    sizeof(gembird_jpd_faulty_rdesc);
+	size_t new_size = *rsize + delta_size;
+
+	if (*rsize >= 31 && !memcmp(&rdesc[GEMBIRD_START_FAULTY_RDESC],
+				    gembird_jpd_faulty_rdesc,
+				    sizeof(gembird_jpd_faulty_rdesc))) {
+		new_rdesc = devm_kzalloc(&hdev->dev, new_size, GFP_KERNEL);
+		if (new_rdesc == NULL)
+			return rdesc;
+
+		dev_info(&hdev->dev,
+			 "fixing Gembird JPD-DualForce 2 report descriptor.\n");
+
+		/* start by copying the end of the rdesc */
+		memcpy(new_rdesc + delta_size, rdesc, *rsize);
+
+		/* add the correct beginning */
+		memcpy(new_rdesc, rdesc, GEMBIRD_START_FAULTY_RDESC);
+
+		/* replace the faulty part with the fixed one */
+		memcpy(new_rdesc + GEMBIRD_START_FAULTY_RDESC,
+		       gembird_jpd_fixed_rdesc,
+		       sizeof(gembird_jpd_fixed_rdesc));
+
+		*rsize = new_size;
+		rdesc = new_rdesc;
+	}
+
+	return rdesc;
+}
+
+static const struct hid_device_id gembird_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_GEMBIRD,
+			 USB_DEVICE_ID_GEMBIRD_JPD_DUALFORCE2) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, gembird_devices);
+
+static struct hid_driver gembird_driver = {
+	.name = "gembird",
+	.id_table = gembird_devices,
+	.report_fixup = gembird_report_fixup,
+};
+module_hid_driver(gembird_driver);
+
+MODULE_AUTHOR("Benjamin Tissoires <benjamin.tissoires@gmail.com>");
+MODULE_DESCRIPTION("HID Gembird joypad driver");
+MODULE_LICENSE("GPL");