From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ming Lei Subject: [PATCH 1/2] usbnet: increase URB reference count before usb_unlink_urb Date: Thu, 22 Mar 2012 21:22:18 +0800 Message-ID: <1332422538-6597-1-git-send-email-tom.leiming@gmail.com> Cc: netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Ming Lei , stable-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, Sebastian Andrzej Siewior , Alan Stern , Oliver Neukum To: "David S. Miller" , Greg Kroah-Hartman Return-path: Sender: linux-usb-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: netdev.vger.kernel.org Commit 4231d47e6fe69f061f96c98c30eaf9fb4c14b96d(net/usbnet: avoid recursive locking in usbnet_stop()) fixes the recursive locking problem by releasing the skb queue lock, but it makes usb_unlink_urb racing with defer_bh, and the URB to being unlinked may be freed before or during calling usb_unlink_urb, so use-after-free problem may be triggerd inside usb_unlink_urb. The patch fixes the use-after-free problem by increasing URB reference count with skb queue lock held before calling usb_unlink_urb, so the URB won't be freed until return from usb_unlink_urb. Cc: stable-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org Cc: Sebastian Andrzej Siewior Cc: Alan Stern Cc: Oliver Neukum Reported-by: Dave Jones Signed-off-by: Ming Lei --- drivers/net/usb/usbnet.c | 9 +++++++++ 1 files changed, 9 insertions(+), 0 deletions(-) diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c index 4b8b52c..febfdce 100644 --- a/drivers/net/usb/usbnet.c +++ b/drivers/net/usb/usbnet.c @@ -589,6 +589,14 @@ static int unlink_urbs (struct usbnet *dev, struct sk_buff_head *q) entry = (struct skb_data *) skb->cb; urb = entry->urb; + /* + * Get reference count of the URB to avoid it to be + * freed during usb_unlink_urb, which may trigger + * use-after-free problem inside usb_unlink_urb since + * usb_unlink_urb is always racing with .complete + * handler(include defer_bh). + */ + usb_get_urb(urb); spin_unlock_irqrestore(&q->lock, flags); // during some PM-driven resume scenarios, // these (async) unlinks complete immediately @@ -597,6 +605,7 @@ static int unlink_urbs (struct usbnet *dev, struct sk_buff_head *q) netdev_dbg(dev->net, "unlink urb err, %d\n", retval); else count++; + usb_put_urb(urb); spin_lock_irqsave(&q->lock, flags); } spin_unlock_irqrestore (&q->lock, flags); -- 1.7.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html