USB: cdc-wdm: fix buffer overflow

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@neukum.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index 97b2c55..fe8c04b 100644 (file)
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -70,6 +70,7 @@ 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
 
@@ -134,6 +135,7 @@ 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);
@@ -164,9 +166,17 @@ 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);
 
@@ -433,6 +443,11 @@ 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)) {
@@ -472,6 +487,7 @@ retry:
                        spin_unlock_irq(&desc->iuspin);
                        goto retry;
                }
+
                if (!desc->reslength) { /* zero length read */
                        dev_dbg(&desc->intf->dev, "%s: zero length - clearing WDM_READ\n", __func__);
                        clear_bit(WDM_READ, &desc->flags);
@@ -926,6 +942,7 @@ 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->wlock);
        mutex_unlock(&desc->rlock);