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USB: cdc-wdm: fix buffer overflow

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>
CC: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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1 parent a57e82a commit c0f5ecee4e741667b2493c742b60b6218d40b3aa Oliver Neukum committed with gregkh Mar 12, 2013
Showing with 20 additions and 3 deletions.
  1. +20 −3 drivers/usb/class/cdc-wdm.c
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23 drivers/usb/class/cdc-wdm.c
@@ -56,6 +56,7 @@ MODULE_DEVICE_TABLE (usb, wdm_ids);
#define WDM_RESPONDING 7
#define WDM_SUSPENDING 8
#define WDM_RESETTING 9
+#define WDM_OVERFLOW 10
#define WDM_MAX 16
@@ -155,6 +156,7 @@ 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);
@@ -185,9 +187,17 @@ 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);
@@ -435,6 +445,11 @@ static ssize_t wdm_read
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)) {
@@ -478,6 +493,7 @@ static ssize_t wdm_read
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);
@@ -1004,6 +1020,7 @@ static int wdm_post_reset(struct usb_interface *intf)
struct wdm_device *desc = wdm_find_device(intf);
int rv;
+ clear_bit(WDM_OVERFLOW, &desc->flags);
clear_bit(WDM_RESETTING, &desc->flags);
rv = recover_from_urb_loss(desc);
mutex_unlock(&desc->wlock);

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