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SubjectRe: [ 111/184] USB: cdc-wdm: fix buffer overflow
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On Tue, 2013-06-04 at 19:23 +0200, Willy Tarreau wrote:
> 2.6.32-longterm review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> 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>
> [bwh: Backported to 2.6.32: adjust context]

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

> Signed-off-by: Willy Tarreau <w@1wt.eu>
> ---
> 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 37f2899..01ae519 100644
> --- a/drivers/usb/class/cdc-wdm.c
> +++ b/drivers/usb/class/cdc-wdm.c
> @@ -52,6 +52,7 @@ MODULE_DEVICE_TABLE (usb, wdm_ids);
> #define WDM_READ 4
> #define WDM_INT_STALL 5
> #define WDM_POLL_RUNNING 6
> +#define WDM_OVERFLOW 10
>
>
> #define WDM_MAX 16
> @@ -115,6 +116,7 @@ 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);
>
> @@ -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;
> + }
> + }
> wake_up(&desc->wait);
>
> set_bit(WDM_READ, &desc->flags);
> @@ -398,6 +408,11 @@ 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)) {
> @@ -440,6 +455,7 @@ 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);
> @@ -844,6 +860,7 @@ 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->plock);
> return 0;

--
Ben Hutchings
Theory and practice are closer in theory than in practice.
- John Levine, moderator of comp.compilers
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