comedi: misc fixes

The driver uses endpoint-sized USB transfer buffers but had no sanity checks on the sizes. This can lead to zero-size-pointer dereferences or overflowed transfer buffers in ni6501_port_command() and ni6501_counter_command() if a (malicious) device has smaller max-packet sizes than expected (or when doing descriptor fuzz testing).

Add the missing sanity checks to probe().

Fixes a03bb00e50ab ("staging: comedi: add NI USB-6501 support")

Cc [email protected] # 3.18

Cc Luca Ellero <[email protected]>

Signed-off-by Johan Hovold <[email protected]>

---
  drivers/comedi/drivers/ni_usb6501.c | 10 ++++++++++
  1 file changed, 10 insertions(+)

drivers/comedi/drivers/ni_usb6501.c +4 -0

index 5b6d9d783b2f..c42987b74b1d 100644
@@ -144,6 +144,10 @@ static const u8 READ_COUNTER_RESPONSE[]	= {0x00, 0x01, 0x00, 0x10,
  					   0x00, 0x00, 0x00, 0x02,
  					   0x00, 0x00, 0x00, 0x00};
 
+/* Largest supported packets */
+static const size_t TX_MAX_SIZE	= sizeof(SET_PORT_DIR_REQUEST);
+static const size_t RX_MAX_SIZE	= sizeof(READ_PORT_RESPONSE);
+
  enum commands {
  	READ_PORT,
  	WRITE_PORT,

@@ -501,6 +505,12 @@ static int ni6501_find_endpoints(struct comedi_device *dev)
  	if (!devpriv->ep_rx || !devpriv->ep_tx)
  		return -ENODEV;

USB transfer buffers are typically mapped for DMA and must not be allocated on the stack or transfers will fail.

Allocate proper transfer buffers in the various command helpers and return an error on short transfers instead of acting on random stack data.

Note that this also fixes a stack info leak on systems where DMA is not used as 32 bytes are always sent to the device regardless of how short the command is.

Fixes 63274cd7d38a ("Staging: comedi: add usb dt9812 driver")

Cc [email protected] # 2.6.29

Signed-off-by Johan Hovold <[email protected]>

---
  drivers/comedi/drivers/dt9812.c | 115 ++++++++++++++++++++++++--------
  1 file changed, 86 insertions(+), 29 deletions(-)

drivers/comedi/drivers/dt9812.c +81 -27

index 634f57730c1e..704b04d2980d 100644
@@ -32,6 +32,7 @@
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/errno.h>
+#include <linux/slab.h>
  #include <linux/uaccess.h>
 
  #include "../comedi_usb.h"

@@ -237,22 +238,42 @@ static int dt9812_read_info(struct comedi_device *dev,
  {
  	struct usb_device *usb = comedi_to_usb_dev(dev);
  	struct dt9812_private *devpriv = dev->private;
-	struct dt9812_usb_cmd cmd;
+	struct dt9812_usb_cmd *cmd;
+	size_t tbuf_size;
  	int count, ret;
+	void *tbuf;
 
-	cmd.cmd = cpu_to_le32(DT9812_R_FLASH_DATA);
-	cmd.u.flash_data_info.address =
+	tbuf_size = max(sizeof(*cmd), buf_size);
+
+	tbuf = kzalloc(tbuf_size, GFP_KERNEL);
+	if (!tbuf)
+		return -ENOMEM;
+
+	cmd = tbuf;
+
+	cmd->cmd = cpu_to_le32(DT9812_R_FLASH_DATA);
+	cmd->u.flash_data_info.address =
  	    cpu_to_le16(DT9812_DIAGS_BOARD_INFO_ADDR + offset);
-	cmd.u.flash_data_info.numbytes = cpu_to_le16(buf_size);
+	cmd->u.flash_data_info.numbytes = cpu_to_le16(buf_size);
 
  	/* DT9812 only responds to 32 byte writes!! */
  	ret = usb_bulk_msg(usb, usb_sndbulkpipe(usb, devpriv->cmd_wr.addr),
-			   &cmd, 32, &count, DT9812_USB_TIMEOUT);
+			   cmd, sizeof(*cmd), &count, DT9812_USB_TIMEOUT);
  	if (ret)
-		return ret;
+		goto out;
+
+	ret = usb_bulk_msg(usb, usb_rcvbulkpipe(usb, devpriv->cmd_rd.addr),
+			   tbuf, buf_size, &count, DT9812_USB_TIMEOUT);
+	if (!ret) {
+		if (count == buf_size)
+			memcpy(buf, tbuf, buf_size);
+		else
+			ret = -EREMOTEIO;
+	}
+out:
+	kfree(tbuf);
 
-	return usb_bulk_msg(usb, usb_rcvbulkpipe(usb, devpriv->cmd_rd.addr),
-			    buf, buf_size, &count, DT9812_USB_TIMEOUT);
+	return ret;
  }
 
  static int dt9812_read_multiple_registers(struct comedi_device *dev,

@@ -261,22 +282,42 @@ static int dt9812_read_multiple_registers(struct comedi_device *dev,
  {
  	struct usb_device *usb = comedi_to_usb_dev(dev);
  	struct dt9812_private *devpriv = dev->private;
-	struct dt9812_usb_cmd cmd;
+	struct dt9812_usb_cmd *cmd;
  	int i, count, ret;
+	size_t buf_size;
+	void *buf;
 
-	cmd.cmd = cpu_to_le32(DT9812_R_MULTI_BYTE_REG);
-	cmd.u.read_multi_info.count = reg_count;
+	buf_size = max_t(size_t, sizeof(*cmd), reg_count);
+
+	buf = kzalloc(buf_size, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	cmd = buf;
+
+	cmd->cmd = cpu_to_le32(DT9812_R_MULTI_BYTE_REG);
+	cmd->u.read_multi_info.count = reg_count;
  	for (i = 0; i < reg_count; i++)
-		cmd.u.read_multi_info.address[i] = address[i];
+		cmd->u.read_multi_info.address[i] = address[i];
 
  	/* DT9812 only responds to 32 byte writes!! */
  	ret = usb_bulk_msg(usb, usb_sndbulkpipe(usb, devpriv->cmd_wr.addr),
-			   &cmd, 32, &count, DT9812_USB_TIMEOUT);
+			   cmd, sizeof(*cmd), &count, DT9812_USB_TIMEOUT);
  	if (ret)
-		return ret;
+		goto out;
+
+	ret = usb_bulk_msg(usb, usb_rcvbulkpipe(usb, devpriv->cmd_rd.addr),
+			   buf, reg_count, &count, DT9812_USB_TIMEOUT);
+	if (!ret) {
+		if (count == reg_count)
+			memcpy(value, buf, reg_count);
+		else
+			ret = -EREMOTEIO;
+	}
+out:
+	kfree(buf);
 
-	return usb_bulk_msg(usb, usb_rcvbulkpipe(usb, devpriv->cmd_rd.addr),
-			    value, reg_count, &count, DT9812_USB_TIMEOUT);
+	return ret;
  }
 
  static int dt9812_write_multiple_registers(struct comedi_device *dev,

@@ -285,19 +326,27 @@ static int dt9812_write_multiple_registers(struct comedi_device *dev,
  {
  	struct usb_device *usb = comedi_to_usb_dev(dev);
  	struct dt9812_private *devpriv = dev->private;
-	struct dt9812_usb_cmd cmd;
+	struct dt9812_usb_cmd *cmd;
  	int i, count;
+	int ret;
+
+	cmd = kzalloc(sizeof(*cmd), GFP_KERNEL);
+	if (!cmd)
+		return -ENOMEM;
 
-	cmd.cmd = cpu_to_le32(DT9812_W_MULTI_BYTE_REG);
-	cmd.u.read_multi_info.count = reg_count;
+	cmd->cmd = cpu_to_le32(DT9812_W_MULTI_BYTE_REG);
+	cmd->u.read_multi_info.count = reg_count;
  	for (i = 0; i < reg_count; i++) {
-		cmd.u.write_multi_info.write[i].address = address[i];
-		cmd.u.write_multi_info.write[i].value = value[i];
+		cmd->u.write_multi_info.write[i].address = address[i];
+		cmd->u.write_multi_info.write[i].value = value[i];
  	}
 
  	/* DT9812 only responds to 32 byte writes!! */
-	return usb_bulk_msg(usb, usb_sndbulkpipe(usb, devpriv->cmd_wr.addr),
-			    &cmd, 32, &count, DT9812_USB_TIMEOUT);
+	ret = usb_bulk_msg(usb, usb_sndbulkpipe(usb, devpriv->cmd_wr.addr),
+			   cmd, sizeof(*cmd), &count, DT9812_USB_TIMEOUT);
+	kfree(cmd);
+
+	return ret;
  }
 
  static int dt9812_rmw_multiple_registers(struct comedi_device *dev,

@@ -306,17 +355,25 @@ static int dt9812_rmw_multiple_registers(struct comedi_device *dev,
  {
  	struct usb_device *usb = comedi_to_usb_dev(dev);
  	struct dt9812_private *devpriv = dev->private;
-	struct dt9812_usb_cmd cmd;
+	struct dt9812_usb_cmd *cmd;
  	int i, count;
+	int ret;
+
+	cmd = kzalloc(sizeof(*cmd), GFP_KERNEL);
+	if (!cmd)
+		return -ENOMEM;
 
-	cmd.cmd = cpu_to_le32(DT9812_RMW_MULTI_BYTE_REG);
-	cmd.u.rmw_multi_info.count = reg_count;
+	cmd->cmd = cpu_to_le32(DT9812_RMW_MULTI_BYTE_REG);
+	cmd->u.rmw_multi_info.count = reg_count;
  	for (i = 0; i < reg_count; i++)
-		cmd.u.rmw_multi_info.rmw[i] = rmw[i];
+		cmd->u.rmw_multi_info.rmw[i] = rmw[i];
 
  	/* DT9812 only responds to 32 byte writes!! */