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, 526 insertions, 0 deletions

diff --git a/drivers/usb/serial/ssu100.c b/drivers/usb/serial/ssu100.c
new file mode 100644
index 000000000..b0d51558b
--- /dev/null
+++ b/drivers/usb/serial/ssu100.c
@@ -0,0 +1,526 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * usb-serial driver for Quatech SSU-100
+ *
+ * based on ftdi_sio.c and the original serqt_usb.c from Quatech
+ *
+ */
+
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+#include <linux/module.h>
+#include <linux/serial.h>
+#include <linux/usb.h>
+#include <linux/usb/serial.h>
+#include <linux/serial_reg.h>
+
+#define QT_OPEN_CLOSE_CHANNEL       0xca
+#define QT_SET_GET_DEVICE           0xc2
+#define QT_SET_GET_REGISTER         0xc0
+#define QT_GET_SET_PREBUF_TRIG_LVL  0xcc
+#define QT_SET_ATF                  0xcd
+#define QT_GET_SET_UART             0xc1
+#define QT_TRANSFER_IN              0xc0
+#define QT_HW_FLOW_CONTROL_MASK     0xc5
+#define QT_SW_FLOW_CONTROL_MASK     0xc6
+
+#define  SERIAL_MSR_MASK            0xf0
+
+#define  SERIAL_CRTSCTS ((UART_MCR_RTS << 8) | UART_MSR_CTS)
+
+#define  SERIAL_EVEN_PARITY         (UART_LCR_PARITY | UART_LCR_EPAR)
+
+#define  MAX_BAUD_RATE              460800
+
+#define ATC_DISABLED                0x00
+#define DUPMODE_BITS        0xc0
+#define RR_BITS             0x03
+#define LOOPMODE_BITS       0x41
+#define RS232_MODE          0x00
+#define RTSCTS_TO_CONNECTOR 0x40
+#define CLKS_X4             0x02
+#define FULLPWRBIT          0x00000080
+#define NEXT_BOARD_POWER_BIT        0x00000004
+
+#define DRIVER_DESC "Quatech SSU-100 USB to Serial Driver"
+
+#define	USB_VENDOR_ID_QUATECH	0x061d	/* Quatech VID */
+#define QUATECH_SSU100	0xC020	/* SSU100 */
+
+static const struct usb_device_id id_table[] = {
+	{USB_DEVICE(USB_VENDOR_ID_QUATECH, QUATECH_SSU100)},
+	{}			/* Terminating entry */
+};
+MODULE_DEVICE_TABLE(usb, id_table);
+
+struct ssu100_port_private {
+	spinlock_t status_lock;
+	u8 shadowLSR;
+	u8 shadowMSR;
+};
+
+static inline int ssu100_control_msg(struct usb_device *dev,
+				     u8 request, u16 data, u16 index)
+{
+	return usb_control_msg(dev, usb_sndctrlpipe(dev, 0),
+			       request, 0x40, data, index,
+			       NULL, 0, 300);
+}
+
+static inline int ssu100_setdevice(struct usb_device *dev, u8 *data)
+{
+	u16 x = ((u16)(data[1] << 8) | (u16)(data[0]));
+
+	return ssu100_control_msg(dev, QT_SET_GET_DEVICE, x, 0);
+}
+
+
+static inline int ssu100_getdevice(struct usb_device *dev, u8 *data)
+{
+	int ret;
+
+	ret = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
+			      QT_SET_GET_DEVICE, 0xc0, 0, 0,
+			      data, 3, 300);
+	if (ret < 3) {
+		if (ret >= 0)
+			ret = -EIO;
+	}
+
+	return ret;
+}
+
+static inline int ssu100_getregister(struct usb_device *dev,
+				     unsigned short uart,
+				     unsigned short reg,
+				     u8 *data)
+{
+	int ret;
+
+	ret = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
+			      QT_SET_GET_REGISTER, 0xc0, reg,
+			      uart, data, sizeof(*data), 300);
+	if (ret < (int)sizeof(*data)) {
+		if (ret >= 0)
+			ret = -EIO;
+	}
+
+	return ret;
+}
+
+
+static inline int ssu100_setregister(struct usb_device *dev,
+				     unsigned short uart,
+				     unsigned short reg,
+				     u16 data)
+{
+	u16 value = (data << 8) | reg;
+
+	return usb_control_msg(dev, usb_sndctrlpipe(dev, 0),
+			       QT_SET_GET_REGISTER, 0x40, value, uart,
+			       NULL, 0, 300);
+
+}
+
+#define set_mctrl(dev, set)		update_mctrl((dev), (set), 0)
+#define clear_mctrl(dev, clear)	update_mctrl((dev), 0, (clear))
+
+/* these do not deal with device that have more than 1 port */
+static inline int update_mctrl(struct usb_device *dev, unsigned int set,
+			       unsigned int clear)
+{
+	unsigned urb_value;
+	int result;
+
+	if (((set | clear) & (TIOCM_DTR | TIOCM_RTS)) == 0) {
+		dev_dbg(&dev->dev, "%s - DTR|RTS not being set|cleared\n", __func__);
+		return 0;	/* no change */
+	}
+
+	clear &= ~set;	/* 'set' takes precedence over 'clear' */
+	urb_value = 0;
+	if (set & TIOCM_DTR)
+		urb_value |= UART_MCR_DTR;
+	if (set & TIOCM_RTS)
+		urb_value |= UART_MCR_RTS;
+
+	result = ssu100_setregister(dev, 0, UART_MCR, urb_value);
+	if (result < 0)
+		dev_dbg(&dev->dev, "%s Error from MODEM_CTRL urb\n", __func__);
+
+	return result;
+}
+
+static int ssu100_initdevice(struct usb_device *dev)
+{
+	u8 *data;
+	int result = 0;
+
+	data = kzalloc(3, GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	result = ssu100_getdevice(dev, data);
+	if (result < 0) {
+		dev_dbg(&dev->dev, "%s - get_device failed %i\n", __func__, result);
+		goto out;
+	}
+
+	data[1] &= ~FULLPWRBIT;
+
+	result = ssu100_setdevice(dev, data);
+	if (result < 0) {
+		dev_dbg(&dev->dev, "%s - setdevice failed %i\n", __func__, result);
+		goto out;
+	}
+
+	result = ssu100_control_msg(dev, QT_GET_SET_PREBUF_TRIG_LVL, 128, 0);
+	if (result < 0) {
+		dev_dbg(&dev->dev, "%s - set prebuffer level failed %i\n", __func__, result);
+		goto out;
+	}
+
+	result = ssu100_control_msg(dev, QT_SET_ATF, ATC_DISABLED, 0);
+	if (result < 0) {
+		dev_dbg(&dev->dev, "%s - set ATFprebuffer level failed %i\n", __func__, result);
+		goto out;
+	}
+
+	result = ssu100_getdevice(dev, data);
+	if (result < 0) {
+		dev_dbg(&dev->dev, "%s - get_device failed %i\n", __func__, result);
+		goto out;
+	}
+
+	data[0] &= ~(RR_BITS | DUPMODE_BITS);
+	data[0] |= CLKS_X4;
+	data[1] &= ~(LOOPMODE_BITS);
+	data[1] |= RS232_MODE;
+
+	result = ssu100_setdevice(dev, data);
+	if (result < 0) {
+		dev_dbg(&dev->dev, "%s - setdevice failed %i\n", __func__, result);
+		goto out;
+	}
+
+out:	kfree(data);
+	return result;
+
+}
+
+
+static void ssu100_set_termios(struct tty_struct *tty,
+		               struct usb_serial_port *port,
+		               const struct ktermios *old_termios)
+{
+	struct usb_device *dev = port->serial->dev;
+	struct ktermios *termios = &tty->termios;
+	u16 baud, divisor, remainder;
+	unsigned int cflag = termios->c_cflag;
+	u16 urb_value = 0; /* will hold the new flags */
+	int result;
+
+	if (cflag & PARENB) {
+		if (cflag & PARODD)
+			urb_value |= UART_LCR_PARITY;
+		else
+			urb_value |= SERIAL_EVEN_PARITY;
+	}
+
+	urb_value |= UART_LCR_WLEN(tty_get_char_size(cflag));
+
+	baud = tty_get_baud_rate(tty);
+	if (!baud)
+		baud = 9600;
+
+	dev_dbg(&port->dev, "%s - got baud = %d\n", __func__, baud);
+
+
+	divisor = MAX_BAUD_RATE / baud;
+	remainder = MAX_BAUD_RATE % baud;
+	if (((remainder * 2) >= baud) && (baud != 110))
+		divisor++;
+
+	urb_value = urb_value << 8;
+
+	result = ssu100_control_msg(dev, QT_GET_SET_UART, divisor, urb_value);
+	if (result < 0)
+		dev_dbg(&port->dev, "%s - set uart failed\n", __func__);
+
+	if (cflag & CRTSCTS)
+		result = ssu100_control_msg(dev, QT_HW_FLOW_CONTROL_MASK,
+					    SERIAL_CRTSCTS, 0);
+	else
+		result = ssu100_control_msg(dev, QT_HW_FLOW_CONTROL_MASK,
+					    0, 0);
+	if (result < 0)
+		dev_dbg(&port->dev, "%s - set HW flow control failed\n", __func__);
+
+	if (I_IXOFF(tty) || I_IXON(tty)) {
+		u16 x = ((u16)(START_CHAR(tty) << 8) | (u16)(STOP_CHAR(tty)));
+
+		result = ssu100_control_msg(dev, QT_SW_FLOW_CONTROL_MASK,
+					    x, 0);
+	} else
+		result = ssu100_control_msg(dev, QT_SW_FLOW_CONTROL_MASK,
+					    0, 0);
+
+	if (result < 0)
+		dev_dbg(&port->dev, "%s - set SW flow control failed\n", __func__);
+
+}
+
+
+static int ssu100_open(struct tty_struct *tty, struct usb_serial_port *port)
+{
+	struct usb_device *dev = port->serial->dev;
+	struct ssu100_port_private *priv = usb_get_serial_port_data(port);
+	u8 *data;
+	int result;
+	unsigned long flags;
+
+	data = kzalloc(2, GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	result = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
+				 QT_OPEN_CLOSE_CHANNEL,
+				 QT_TRANSFER_IN, 0x01,
+				 0, data, 2, 300);
+	if (result < 2) {
+		dev_dbg(&port->dev, "%s - open failed %i\n", __func__, result);
+		if (result >= 0)
+			result = -EIO;
+		kfree(data);
+		return result;
+	}
+
+	spin_lock_irqsave(&priv->status_lock, flags);
+	priv->shadowLSR = data[0];
+	priv->shadowMSR = data[1];
+	spin_unlock_irqrestore(&priv->status_lock, flags);
+
+	kfree(data);
+
+/* set to 9600 */
+	result = ssu100_control_msg(dev, QT_GET_SET_UART, 0x30, 0x0300);
+	if (result < 0)
+		dev_dbg(&port->dev, "%s - set uart failed\n", __func__);
+
+	if (tty)
+		ssu100_set_termios(tty, port, &tty->termios);
+
+	return usb_serial_generic_open(tty, port);
+}
+
+static int ssu100_attach(struct usb_serial *serial)
+{
+	return ssu100_initdevice(serial->dev);
+}
+
+static int ssu100_port_probe(struct usb_serial_port *port)
+{
+	struct ssu100_port_private *priv;
+
+	priv = kzalloc_obj(*priv);
+	if (!priv)
+		return -ENOMEM;
+
+	spin_lock_init(&priv->status_lock);
+
+	usb_set_serial_port_data(port, priv);
+
+	return 0;
+}
+
+static void ssu100_port_remove(struct usb_serial_port *port)
+{
+	struct ssu100_port_private *priv;
+
+	priv = usb_get_serial_port_data(port);
+	kfree(priv);
+}
+
+static int ssu100_tiocmget(struct tty_struct *tty)
+{
+	struct usb_serial_port *port = tty->driver_data;
+	struct usb_device *dev = port->serial->dev;
+	u8 *d;
+	int r;
+
+	d = kzalloc(2, GFP_KERNEL);
+	if (!d)
+		return -ENOMEM;
+
+	r = ssu100_getregister(dev, 0, UART_MCR, d);
+	if (r < 0)
+		goto mget_out;
+
+	r = ssu100_getregister(dev, 0, UART_MSR, d+1);
+	if (r < 0)
+		goto mget_out;
+
+	r = (d[0] & UART_MCR_DTR ? TIOCM_DTR : 0) |
+		(d[0] & UART_MCR_RTS ? TIOCM_RTS : 0) |
+		(d[1] & UART_MSR_CTS ? TIOCM_CTS : 0) |
+		(d[1] & UART_MSR_DCD ? TIOCM_CAR : 0) |
+		(d[1] & UART_MSR_RI ? TIOCM_RI : 0) |
+		(d[1] & UART_MSR_DSR ? TIOCM_DSR : 0);
+
+mget_out:
+	kfree(d);
+	return r;
+}
+
+static int ssu100_tiocmset(struct tty_struct *tty,
+			   unsigned int set, unsigned int clear)
+{
+	struct usb_serial_port *port = tty->driver_data;
+	struct usb_device *dev = port->serial->dev;
+
+	return update_mctrl(dev, set, clear);
+}
+
+static void ssu100_dtr_rts(struct usb_serial_port *port, int on)
+{
+	struct usb_device *dev = port->serial->dev;
+
+	/* Disable flow control */
+	if (!on) {
+		if (ssu100_setregister(dev, 0, UART_MCR, 0) < 0)
+			dev_err(&port->dev, "error from flowcontrol urb\n");
+	}
+	/* drop RTS and DTR */
+	if (on)
+		set_mctrl(dev, TIOCM_DTR | TIOCM_RTS);
+	else
+		clear_mctrl(dev, TIOCM_DTR | TIOCM_RTS);
+}
+
+static void ssu100_update_msr(struct usb_serial_port *port, u8 msr)
+{
+	struct ssu100_port_private *priv = usb_get_serial_port_data(port);
+	unsigned long flags;
+
+	spin_lock_irqsave(&priv->status_lock, flags);
+	priv->shadowMSR = msr;
+	spin_unlock_irqrestore(&priv->status_lock, flags);
+
+	if (msr & UART_MSR_ANY_DELTA) {
+		/* update input line counters */
+		if (msr & UART_MSR_DCTS)
+			port->icount.cts++;
+		if (msr & UART_MSR_DDSR)
+			port->icount.dsr++;
+		if (msr & UART_MSR_DDCD)
+			port->icount.dcd++;
+		if (msr & UART_MSR_TERI)
+			port->icount.rng++;
+		wake_up_interruptible(&port->port.delta_msr_wait);
+	}
+}
+
+static void ssu100_update_lsr(struct usb_serial_port *port, u8 lsr,
+			      char *tty_flag)
+{
+	struct ssu100_port_private *priv = usb_get_serial_port_data(port);
+	unsigned long flags;
+
+	spin_lock_irqsave(&priv->status_lock, flags);
+	priv->shadowLSR = lsr;
+	spin_unlock_irqrestore(&priv->status_lock, flags);
+
+	*tty_flag = TTY_NORMAL;
+	if (lsr & UART_LSR_BRK_ERROR_BITS) {
+		/* we always want to update icount, but we only want to
+		 * update tty_flag for one case */
+		if (lsr & UART_LSR_BI) {
+			port->icount.brk++;
+			*tty_flag = TTY_BREAK;
+			usb_serial_handle_break(port);
+		}
+		if (lsr & UART_LSR_PE) {
+			port->icount.parity++;
+			if (*tty_flag == TTY_NORMAL)
+				*tty_flag = TTY_PARITY;
+		}
+		if (lsr & UART_LSR_FE) {
+			port->icount.frame++;
+			if (*tty_flag == TTY_NORMAL)
+				*tty_flag = TTY_FRAME;
+		}
+		if (lsr & UART_LSR_OE) {
+			port->icount.overrun++;
+			tty_insert_flip_char(&port->port, 0, TTY_OVERRUN);
+		}
+	}
+
+}
+
+static void ssu100_process_read_urb(struct urb *urb)
+{
+	struct usb_serial_port *port = urb->context;
+	char *packet = urb->transfer_buffer;
+	char flag = TTY_NORMAL;
+	u32 len = urb->actual_length;
+	int i;
+	char *ch;
+
+	if ((len >= 4) &&
+	    (packet[0] == 0x1b) && (packet[1] == 0x1b) &&
+	    ((packet[2] == 0x00) || (packet[2] == 0x01))) {
+		if (packet[2] == 0x00)
+			ssu100_update_lsr(port, packet[3], &flag);
+		if (packet[2] == 0x01)
+			ssu100_update_msr(port, packet[3]);
+
+		len -= 4;
+		ch = packet + 4;
+	} else
+		ch = packet;
+
+	if (!len)
+		return;	/* status only */
+
+	if (port->sysrq) {
+		for (i = 0; i < len; i++, ch++) {
+			if (!usb_serial_handle_sysrq_char(port, *ch))
+				tty_insert_flip_char(&port->port, *ch, flag);
+		}
+	} else {
+		tty_insert_flip_string_fixed_flag(&port->port, ch, flag, len);
+	}
+
+	tty_flip_buffer_push(&port->port);
+}
+
+static struct usb_serial_driver ssu100_device = {
+	.driver = {
+		.name = "ssu100",
+	},
+	.description	     = DRIVER_DESC,
+	.id_table	     = id_table,
+	.num_ports	     = 1,
+	.open		     = ssu100_open,
+	.attach              = ssu100_attach,
+	.port_probe          = ssu100_port_probe,
+	.port_remove         = ssu100_port_remove,
+	.dtr_rts             = ssu100_dtr_rts,
+	.process_read_urb    = ssu100_process_read_urb,
+	.tiocmget            = ssu100_tiocmget,
+	.tiocmset            = ssu100_tiocmset,
+	.tiocmiwait          = usb_serial_generic_tiocmiwait,
+	.get_icount	     = usb_serial_generic_get_icount,
+	.set_termios         = ssu100_set_termios,
+};
+
+static struct usb_serial_driver * const serial_drivers[] = {
+	&ssu100_device, NULL
+};
+
+module_usb_serial_driver(serial_drivers, id_table);
+
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL v2");