[ 05/48] USB: cdc-wdm: fix buffer overflow

Greg Kroah-Hartman
2013-03-18T21:44:46Z

From: Oliver Neukum <oneukum@suse.de>

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>

---
drivers/usb/class/cdc-wdm.c | 23 ++++++++++++++++++++---
1 file changed, 20 insertions(+), 3 deletions(-)

--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -81,6 +81,7 @@ 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

@@ -180,6 +181,7 @@ static void wdm_in_callback(struct 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);
@@ -210,9 +212,17 @@ static void wdm_in_callback(struct 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);

@@ -457,6 +467,11 @@ 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)) {
@@ -500,6 +515,7 @@ 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);
@@ -1023,6 +1039,7 @@ static int wdm_post_reset(struct usb_int
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);