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, 41 insertions, 0 deletions

diff --git a/drivers/hid/hid-semitek.c b/drivers/hid/hid-semitek.c
new file mode 100644
index 000000000..4fbec5fd8
--- /dev/null
+++ b/drivers/hid/hid-semitek.c
@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  HID driver for Semitek keyboards
+ *
+ *  Copyright (c) 2021 Benjamin Moody
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+static const __u8 *semitek_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+					unsigned int *rsize)
+{
+	/* In the report descriptor for interface 2, fix the incorrect
+	   description of report ID 0x04 (the report contains a
+	   bitmask, not an array of keycodes.) */
+	if (*rsize == 0xcb && rdesc[0x83] == 0x81 && rdesc[0x84] == 0x00) {
+		hid_info(hdev, "fixing up Semitek report descriptor\n");
+		rdesc[0x84] = 0x02;
+	}
+	return rdesc;
+}
+
+static const struct hid_device_id semitek_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_SEMITEK, USB_DEVICE_ID_SEMITEK_KEYBOARD) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, semitek_devices);
+
+static struct hid_driver semitek_driver = {
+	.name = "semitek",
+	.id_table = semitek_devices,
+	.report_fixup = semitek_report_fixup,
+};
+module_hid_driver(semitek_driver);
+
+MODULE_DESCRIPTION("HID driver for Semitek keyboards");
+MODULE_LICENSE("GPL");