[PATCH 3.12 024/142] USB: whiteheat: Added bounds checking for bulk command response

[Jiri Slaby]

From: James Forshaw <forshaw@xxxxxxxxxx>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 6817ae225cd650fb1c3295d769298c38b1eba818 upstream.

This patch fixes a potential security issue in the whiteheat USB driver
which might allow a local attacker to cause kernel memory corrpution. This
is due to an unchecked memcpy into a fixed size buffer (of 64 bytes). On
EHCI and XHCI busses it's possible to craft responses greater than 64
bytes leading a buffer overflow.

Signed-off-by: James Forshaw <forshaw@xxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
 drivers/usb/serial/whiteheat.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/serial/whiteheat.c b/drivers/usb/serial/whiteheat.c
index 36a7740e827c..cc5a430dc357 100644
--- a/drivers/usb/serial/whiteheat.c
+++ b/drivers/usb/serial/whiteheat.c
@@ -521,6 +521,10 @@ static void command_port_read_callback(struct urb *urb)
 		dev_dbg(&urb->dev->dev, "%s - command_info is NULL, exiting.\n", __func__);
 		return;
 	}
+	if (!urb->actual_length) {
+		dev_dbg(&urb->dev->dev, "%s - empty response, exiting.\n", __func__);
+		return;
+	}
 	if (status) {
 		dev_dbg(&urb->dev->dev, "%s - nonzero urb status: %d\n", __func__, status);
 		if (status != -ENOENT)
@@ -541,7 +545,8 @@ static void command_port_read_callback(struct urb *urb)
 		/* These are unsolicited reports from the firmware, hence no
 		   waiting command to wakeup */
 		dev_dbg(&urb->dev->dev, "%s - event received\n", __func__);
-	} else if (data[0] == WHITEHEAT_GET_DTR_RTS) {
+	} else if ((data[0] == WHITEHEAT_GET_DTR_RTS) &&
+		(urb->actual_length - 1 <= sizeof(command_info->result_buffer))) {
 		memcpy(command_info->result_buffer, &data[1],
 						urb->actual_length - 1);
 		command_info->command_finished = WHITEHEAT_CMD_COMPLETE;
-- 
2.1.0

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