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, 166 insertions, 0 deletions

diff --git a/drivers/hid/hid-maltron.c b/drivers/hid/hid-maltron.c
new file mode 100644
index 000000000..f0aad1ba2
--- /dev/null
+++ b/drivers/hid/hid-maltron.c
@@ -0,0 +1,166 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * HID driver for Maltron L90
+ *
+ * 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) 2008 Jiri Slaby
+ * Copyright (c) 2012 David Dillow <dave@thedillows.org>
+ * Copyright (c) 2006-2013 Jiri Kosina
+ * Copyright (c) 2013 Colin Leitner <colin.leitner@gmail.com>
+ * Copyright (c) 2014-2016 Frank Praznik <frank.praznik@gmail.com>
+ * Copyright (c) 2010 Richard Nauber <Richard.Nauber@gmail.com>
+ * Copyright (c) 2016 Yuxuan Shui <yshuiv7@gmail.com>
+ * Copyright (c) 2018 William Whistler <wtbw@wtbw.co.uk>
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+/* The original buggy USB descriptor */
+static const u8 maltron_rdesc_o[] = {
+	0x05, 0x01,        /* Usage Page (Generic Desktop Ctrls) */
+	0x09, 0x80,        /* Usage (Sys Control)                */
+	0xA1, 0x01,        /* Collection (Application)           */
+	0x85, 0x02,        /*   Report ID (2)                    */
+	0x75, 0x01,        /*   Report Size (1)                  */
+	0x95, 0x01,        /*   Report Count (1)                 */
+	0x15, 0x00,        /*   Logical Minimum (0)              */
+	0x25, 0x01,        /*   Logical Maximum (1)              */
+	0x09, 0x82,        /*   Usage (Sys Sleep)                */
+	0x81, 0x06,        /*   Input (Data,Var,Rel)             */
+	0x09, 0x82,        /*   Usage (Sys Sleep)                */
+	0x81, 0x06,        /*   Input (Data,Var,Rel)             */
+	0x09, 0x83,        /*   Usage (Sys Wake Up)              */
+	0x81, 0x06,        /*   Input (Data,Var,Rel)             */
+	0x75, 0x05,        /*   Report Size (5)                  */
+	0x81, 0x01,        /*   Input (Const,Array,Abs)          */
+	0xC0,              /* End Collection                     */
+	0x05, 0x0C,        /* Usage Page (Consumer)              */
+	0x09, 0x01,        /* Usage (Consumer Control)           */
+	0xA1, 0x01,        /* Collection (Application)           */
+	0x85, 0x03,        /*   Report ID (3)                    */
+	0x95, 0x01,        /*   Report Count (1)                 */
+	0x75, 0x10,        /*   Report Size (16)                 */
+	0x19, 0x00,        /*   Usage Minimum (Unassigned)       */
+	0x2A, 0xFF, 0x7F,  /*   Usage Maximum (0x7FFF)           */
+	0x81, 0x00,        /*   Input (Data,Array,Abs)           */
+	0xC0,              /* End Collection                     */
+	0x06, 0x7F, 0xFF,  /* Usage Page (Vendor Defined 0xFF7F) */
+	0x09, 0x01,        /* Usage (0x01)                       */
+	0xA1, 0x01,        /* Collection (Application)           */
+	0x85, 0x04,        /*   Report ID (4)                    */
+	0x95, 0x01,        /*   Report Count (1)                 */
+	0x75, 0x10,        /*   Report Size (16)                 */
+	0x19, 0x00,        /*   Usage Minimum (0x00)             */
+	0x2A, 0xFF, 0x7F,  /*   Usage Maximum (0x7FFF)           */
+	0x81, 0x00,        /*   Input (Data,Array,Abs)           */
+	0x75, 0x02,        /*   Report Size (2)                  */
+	0x25, 0x02,        /*   Logical Maximum (2)              */
+	0x09, 0x90,        /*   Usage (0x90)                     */
+	0xB1, 0x02,        /*   Feature (Data,Var,Abs)           */
+	0x75, 0x06,        /*   Report Size (6)                  */
+	0xB1, 0x01,        /*   Feature (Const,Array,Abs)        */
+	0x75, 0x01,        /*   Report Size (1)                  */
+	0x25, 0x01,        /*   Logical Maximum (1)              */
+	0x05, 0x08,        /*   Usage Page (LEDs)                */
+	0x09, 0x2A,        /*   Usage (On-Line)                  */
+	0x91, 0x02,        /*   Output (Data,Var,Abs)            */
+	0x09, 0x4B,        /*   Usage (Generic Indicator)        */
+	0x91, 0x02,        /*   Output (Data,Var,Abs)            */
+	0x75, 0x06,        /*   Report Size (6)                  */
+	0x95, 0x01,        /*   Report Count (1)                 */
+	0x91, 0x01,        /*   Output (Const,Array,Abs)         */
+	0xC0               /* End Collection                     */
+};
+
+/* The patched descriptor, allowing media key events to be accepted as valid */
+static const u8 maltron_rdesc[] = {
+	0x05, 0x01,        /* Usage Page (Generic Desktop Ctrls) */
+	0x09, 0x80,        /* Usage (Sys Control)                */
+	0xA1, 0x01,        /* Collection (Application)           */
+	0x85, 0x02,        /*   Report ID (2)                    */
+	0x75, 0x01,        /*   Report Size (1)                  */
+	0x95, 0x01,        /*   Report Count (1)                 */
+	0x15, 0x00,        /*   Logical Minimum (0)              */
+	0x25, 0x01,        /*   Logical Maximum (1)              */
+	0x09, 0x82,        /*   Usage (Sys Sleep)                */
+	0x81, 0x06,        /*   Input (Data,Var,Rel)             */
+	0x09, 0x82,        /*   Usage (Sys Sleep)                */
+	0x81, 0x06,        /*   Input (Data,Var,Rel)             */
+	0x09, 0x83,        /*   Usage (Sys Wake Up)              */
+	0x81, 0x06,        /*   Input (Data,Var,Rel)             */
+	0x75, 0x05,        /*   Report Size (5)                  */
+	0x81, 0x01,        /*   Input (Const,Array,Abs)          */
+	0xC0,              /* End Collection                     */
+	0x05, 0x0C,        /* Usage Page (Consumer)              */
+	0x09, 0x01,        /* Usage (Consumer Control)           */
+	0xA1, 0x01,        /* Collection (Application)           */
+	0x85, 0x03,        /*   Report ID (3)                    */
+	0x15, 0x00,        /*   Logical Minimum (0)              - changed */
+	0x26, 0xFF, 0x7F,  /*   Logical Maximum (32767)          - changed */
+	0x95, 0x01,        /*   Report Count (1)                 */
+	0x75, 0x10,        /*   Report Size (16)                 */
+	0x19, 0x00,        /*   Usage Minimum (Unassigned)       */
+	0x2A, 0xFF, 0x7F,  /*   Usage Maximum (0x7FFF)           */
+	0x81, 0x00,        /*   Input (Data,Array,Abs)           */
+	0xC0,              /* End Collection                     */
+	0x06, 0x7F, 0xFF,  /* Usage Page (Vendor Defined 0xFF7F) */
+	0x09, 0x01,        /* Usage (0x01)                       */
+	0xA1, 0x01,        /* Collection (Application)           */
+	0x85, 0x04,        /*   Report ID (4)                    */
+	0x95, 0x01,        /*   Report Count (1)                 */
+	0x75, 0x10,        /*   Report Size (16)                 */
+	0x19, 0x00,        /*   Usage Minimum (0x00)             */
+	0x2A, 0xFF, 0x7F,  /*   Usage Maximum (0x7FFF)           */
+	0x81, 0x00,        /*   Input (Data,Array,Abs)           */
+	0x75, 0x02,        /*   Report Size (2)                  */
+	0x25, 0x02,        /*   Logical Maximum (2)              */
+	0x09, 0x90,        /*   Usage (0x90)                     */
+	0xB1, 0x02,        /*   Feature (Data,Var,Abs)           */
+	0x75, 0x06,        /*   Report Size (6)                  */
+	0xB1, 0x01,        /*   Feature (Const,Array,Abs)        */
+	0x75, 0x01,        /*   Report Size (1)                  */
+	0x25, 0x01,        /*   Logical Maximum (1)              */
+	0x05, 0x08,        /*   Usage Page (LEDs)                */
+	0x09, 0x2A,        /*   Usage (On-Line)                  */
+	0x91, 0x02,        /*   Output (Data,Var,Abs)            */
+	0x09, 0x4B,        /*   Usage (Generic Indicator)        */
+	0x91, 0x02,        /*   Output (Data,Var,Abs)            */
+	0x75, 0x06,        /*   Report Size (6)                  */
+	0x95, 0x01,        /*   Report Count (1)                 */
+	0x91, 0x01,        /*   Output (Const,Array,Abs)         */
+	0xC0               /* End Collection                     */
+};
+
+static const __u8 *maltron_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+					unsigned int *rsize)
+{
+	if (*rsize == sizeof(maltron_rdesc_o) &&
+	    !memcmp(maltron_rdesc_o, rdesc, sizeof(maltron_rdesc_o))) {
+		hid_info(hdev, "Replacing Maltron L90 keyboard report descriptor\n");
+		*rsize = sizeof(maltron_rdesc);
+		return maltron_rdesc;
+	}
+	return rdesc;
+}
+
+static const struct hid_device_id maltron_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ALCOR, USB_DEVICE_ID_ALCOR_MALTRON_KB)},
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, maltron_devices);
+
+static struct hid_driver maltron_driver = {
+	.name = "maltron",
+	.id_table = maltron_devices,
+	.report_fixup = maltron_report_fixup
+};
+module_hid_driver(maltron_driver);
+
+MODULE_DESCRIPTION("HID driver for Maltron L90");
+MODULE_LICENSE("GPL");