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From: Johan Hovold <johan@kernel.org>
To: Ian Abbott <abbotti@mev.co.uk>,
	H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
	Johan Hovold <johan@kernel.org>,
	stable@vger.kernel.org
Subject: [PATCH v2 2/2] comedi: dt9812: fix DMA buffers on stack
Date: Wed, 27 Oct 2021 11:35:29 +0200	[thread overview]
Message-ID: <20211027093529.30896-3-johan@kernel.org> (raw)
In-Reply-To: <20211027093529.30896-1-johan@kernel.org>

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: stable@vger.kernel.org      # 2.6.29
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/comedi/drivers/dt9812.c | 115 ++++++++++++++++++++++++--------
 1 file changed, 86 insertions(+), 29 deletions(-)

diff --git a/drivers/comedi/drivers/dt9812.c b/drivers/comedi/drivers/dt9812.c
index 634f57730c1e..704b04d2980d 100644
--- a/drivers/comedi/drivers/dt9812.c
+++ b/drivers/comedi/drivers/dt9812.c
@@ -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!! */
-	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_digital_in(struct comedi_device *dev, u8 *bits)
-- 
2.32.0


  parent reply	other threads:[~2021-10-27  9:37 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-27  9:35 [PATCH v2 0/2] comedi: misc fixes Johan Hovold
2021-10-27  9:35 ` [PATCH v2 1/2] comedi: ni_usb6501: fix NULL-deref in command paths Johan Hovold
2021-10-28  9:44   ` Ian Abbott
2021-10-27  9:35 ` Johan Hovold [this message]
2021-10-28  9:45   ` [PATCH v2 2/2] comedi: dt9812: fix DMA buffers on stack Ian Abbott

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