From bdef0ae05e53c9681bdb3367ca1d461e8c2277f5 Mon Sep 17 00:00:00 2001 From: Benedikt Spranger Date: Fri, 12 Oct 2007 15:18:59 -0700 Subject: [PATCH] usb-gadget-ether: prevent oops caused by error interrupt race patch 5395353e0c8272fe73ac914acd7e4add0da2bef0 in mainline. Fix a longstanding race in the Ethernet gadget driver, which can cause an oops on device disconnect. The fix is just to make the TX path check whether its freelist is empty. That check is otherwise not necessary, since the queue is always stopped when that list empties (and restarted when request completion puts an entry back on that freelist). The race window starts when the network code decides to transmit a packet, and ends when hard_start_xmit() grabs the freelist lock. When disconnect() is called inside that window, it shuts down the TX queue and breaks the otherwise-solid assumption that packets are never sent through a TX queue that's stopped. Signed-off-by: Benedikt Spranger Signed-off-by: Thomas Gleixner Signed-off-by: David Brownell Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- drivers/usb/gadget/ether.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/usb/gadget/ether.c b/drivers/usb/gadget/ether.c index 593e23507b1a..d57de878a5f0 100644 --- a/drivers/usb/gadget/ether.c +++ b/drivers/usb/gadget/ether.c @@ -1989,8 +1989,20 @@ static int eth_start_xmit (struct sk_buff *skb, struct net_device *net) } spin_lock_irqsave(&dev->req_lock, flags); + /* + * this freelist can be empty if an interrupt triggered disconnect() + * and reconfigured the gadget (shutting down this queue) after the + * network stack decided to xmit but before we got the spinlock. + */ + if (list_empty(&dev->tx_reqs)) { + spin_unlock_irqrestore(&dev->req_lock, flags); + return 1; + } + req = container_of (dev->tx_reqs.next, struct usb_request, list); list_del (&req->list); + + /* temporarily stop TX queue when the freelist empties */ if (list_empty (&dev->tx_reqs)) netif_stop_queue (net); spin_unlock_irqrestore(&dev->req_lock, flags); -- 2.39.5