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, 191 insertions, 0 deletions

diff --git a/drivers/usb/serial/symbolserial.c b/drivers/usb/serial/symbolserial.c
new file mode 100644
index 000000000..8823671a9
--- /dev/null
+++ b/drivers/usb/serial/symbolserial.c
@@ -0,0 +1,191 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Symbol USB barcode to serial driver
+ *
+ * Copyright (C) 2013 Johan Hovold <jhovold@gmail.com>
+ * Copyright (C) 2009 Greg Kroah-Hartman <gregkh@suse.de>
+ * Copyright (C) 2009 Novell Inc.
+ */
+
+#include <linux/kernel.h>
+#include <linux/tty.h>
+#include <linux/slab.h>
+#include <linux/tty_flip.h>
+#include <linux/module.h>
+#include <linux/usb.h>
+#include <linux/usb/serial.h>
+
+static const struct usb_device_id id_table[] = {
+	{ USB_DEVICE(0x05e0, 0x0600) },
+	{ },
+};
+MODULE_DEVICE_TABLE(usb, id_table);
+
+struct symbol_private {
+	spinlock_t lock;	/* protects the following flags */
+	bool throttled;
+	bool actually_throttled;
+};
+
+static void symbol_int_callback(struct urb *urb)
+{
+	struct usb_serial_port *port = urb->context;
+	struct symbol_private *priv = usb_get_serial_port_data(port);
+	unsigned char *data = urb->transfer_buffer;
+	int status = urb->status;
+	unsigned long flags;
+	int result;
+	int data_length;
+
+	switch (status) {
+	case 0:
+		/* success */
+		break;
+	case -ECONNRESET:
+	case -ENOENT:
+	case -ESHUTDOWN:
+		/* this urb is terminated, clean up */
+		dev_dbg(&port->dev, "%s - urb shutting down with status: %d\n",
+			__func__, status);
+		return;
+	default:
+		dev_dbg(&port->dev, "%s - nonzero urb status received: %d\n",
+			__func__, status);
+		goto exit;
+	}
+
+	usb_serial_debug_data(&port->dev, __func__, urb->actual_length, data);
+
+	/*
+	 * Data from the device comes with a 1 byte header:
+	 *
+	 * <size of data> <data>...
+	 */
+	if (urb->actual_length > 1) {
+		data_length = data[0];
+		if (data_length > (urb->actual_length - 1))
+			data_length = urb->actual_length - 1;
+		tty_insert_flip_string(&port->port, &data[1], data_length);
+		tty_flip_buffer_push(&port->port);
+	} else {
+		dev_dbg(&port->dev, "%s - short packet\n", __func__);
+	}
+
+exit:
+	spin_lock_irqsave(&priv->lock, flags);
+
+	/* Continue trying to always read if we should */
+	if (!priv->throttled) {
+		result = usb_submit_urb(port->interrupt_in_urb, GFP_ATOMIC);
+		if (result)
+			dev_err(&port->dev,
+			    "%s - failed resubmitting read urb, error %d\n",
+							__func__, result);
+	} else
+		priv->actually_throttled = true;
+	spin_unlock_irqrestore(&priv->lock, flags);
+}
+
+static int symbol_open(struct tty_struct *tty, struct usb_serial_port *port)
+{
+	struct symbol_private *priv = usb_get_serial_port_data(port);
+	unsigned long flags;
+	int result = 0;
+
+	spin_lock_irqsave(&priv->lock, flags);
+	priv->throttled = false;
+	priv->actually_throttled = false;
+	spin_unlock_irqrestore(&priv->lock, flags);
+
+	/* Start reading from the device */
+	result = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
+	if (result)
+		dev_err(&port->dev,
+			"%s - failed resubmitting read urb, error %d\n",
+			__func__, result);
+	return result;
+}
+
+static void symbol_close(struct usb_serial_port *port)
+{
+	usb_kill_urb(port->interrupt_in_urb);
+}
+
+static void symbol_throttle(struct tty_struct *tty)
+{
+	struct usb_serial_port *port = tty->driver_data;
+	struct symbol_private *priv = usb_get_serial_port_data(port);
+
+	spin_lock_irq(&priv->lock);
+	priv->throttled = true;
+	spin_unlock_irq(&priv->lock);
+}
+
+static void symbol_unthrottle(struct tty_struct *tty)
+{
+	struct usb_serial_port *port = tty->driver_data;
+	struct symbol_private *priv = usb_get_serial_port_data(port);
+	int result;
+	bool was_throttled;
+
+	spin_lock_irq(&priv->lock);
+	priv->throttled = false;
+	was_throttled = priv->actually_throttled;
+	priv->actually_throttled = false;
+	spin_unlock_irq(&priv->lock);
+
+	if (was_throttled) {
+		result = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
+		if (result)
+			dev_err(&port->dev,
+				"%s - failed submitting read urb, error %d\n",
+							__func__, result);
+	}
+}
+
+static int symbol_port_probe(struct usb_serial_port *port)
+{
+	struct symbol_private *priv;
+
+	priv = kzalloc_obj(*priv);
+	if (!priv)
+		return -ENOMEM;
+
+	spin_lock_init(&priv->lock);
+
+	usb_set_serial_port_data(port, priv);
+
+	return 0;
+}
+
+static void symbol_port_remove(struct usb_serial_port *port)
+{
+	struct symbol_private *priv = usb_get_serial_port_data(port);
+
+	kfree(priv);
+}
+
+static struct usb_serial_driver symbol_device = {
+	.driver = {
+		.name =		"symbol",
+	},
+	.id_table =		id_table,
+	.num_ports =		1,
+	.num_interrupt_in =	1,
+	.port_probe =		symbol_port_probe,
+	.port_remove =		symbol_port_remove,
+	.open =			symbol_open,
+	.close =		symbol_close,
+	.throttle = 		symbol_throttle,
+	.unthrottle =		symbol_unthrottle,
+	.read_int_callback =	symbol_int_callback,
+};
+
+static struct usb_serial_driver * const serial_drivers[] = {
+	&symbol_device, NULL
+};
+
+module_usb_serial_driver(serial_drivers, id_table);
+
+MODULE_DESCRIPTION("Symbol USB barcode to serial driver");
+MODULE_LICENSE("GPL v2");