[v2.6.34-stable 148/213] USB: cdc-wdm: fix buffer overflow

[Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>]

From: Oliver Neukum <oneukum@xxxxxxx>

                   -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
    If you see a problem with using this for longterm, please comment.
                   -------------------

commit c0f5ecee4e741667b2493c742b60b6218d40b3aa upstream.

The buffer for responses must not overflow.
If this would happen, set a flag, drop the data and return
an error after user space has read all remaining data.

Signed-off-by: Oliver Neukum <oliver@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
[PG: minor adjustment since RESET from 880442027569 isn't in .34]
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
---
 drivers/usb/class/cdc-wdm.c | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index 189141ca4e05..ce1af28e54ff 100644
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -54,6 +54,7 @@ MODULE_DEVICE_TABLE (usb, wdm_ids);
 #define WDM_POLL_RUNNING	6
 #define WDM_RESPONDING		7
 #define WDM_SUSPENDING		8
+#define WDM_OVERFLOW		10
 
 #define WDM_MAX			16
 
@@ -114,6 +115,7 @@ static void wdm_in_callback(struct urb *urb)
 {
 	struct wdm_device *desc = urb->context;
 	int status = urb->status;
+	int length = urb->actual_length;
 
 	spin_lock(&desc->iuspin);
 	clear_bit(WDM_RESPONDING, &desc->flags);
@@ -144,9 +146,17 @@ static void wdm_in_callback(struct urb *urb)
 	}
 
 	desc->rerr = status;
-	desc->reslength = urb->actual_length;
-	memmove(desc->ubuf + desc->length, desc->inbuf, desc->reslength);
-	desc->length += desc->reslength;
+	if (length + desc->length > desc->wMaxCommand) {
+		/* The buffer would overflow */
+		set_bit(WDM_OVERFLOW, &desc->flags);
+	} else {
+		/* we may already be in overflow */
+		if (!test_bit(WDM_OVERFLOW, &desc->flags)) {
+			memmove(desc->ubuf + desc->length, desc->inbuf, length);
+			desc->length += length;
+			desc->reslength = length;
+		}
+	}
 skip_error:
 	wake_up(&desc->wait);
 
@@ -410,6 +420,11 @@ retry:
 			rv = -ENODEV;
 			goto err;
 		}
+		if (test_bit(WDM_OVERFLOW, &desc->flags)) {
+			clear_bit(WDM_OVERFLOW, &desc->flags);
+			rv = -ENOBUFS;
+			goto err;
+		}
 		i++;
 		if (file->f_flags & O_NONBLOCK) {
 			if (!test_bit(WDM_READ, &desc->flags)) {
@@ -449,6 +464,7 @@ retry:
 			spin_unlock_irq(&desc->iuspin);
 			goto retry;
 		}
+
 		if (!desc->reslength) { /* zero length read */
 			spin_unlock_irq(&desc->iuspin);
 			goto retry;
@@ -860,6 +876,7 @@ static int wdm_post_reset(struct usb_interface *intf)
 	struct wdm_device *desc = usb_get_intfdata(intf);
 	int rv;
 
+	clear_bit(WDM_OVERFLOW, &desc->flags);
 	rv = recover_from_urb_loss(desc);
 	mutex_unlock(&desc->lock);
 	return 0;
-- 
1.8.5.2

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