x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

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");