From 52c28541efcc9d5bd0a4cb223aade27ed81422bb Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Fri, 30 Jan 2015 12:58:26 -0500 Subject: [PATCH] USB: fix use-after-free bug in usb_hcd_unlink_urb() commit c99197902da284b4b723451c1471c45b18537cde upstream. The usb_hcd_unlink_urb() routine in hcd.c contains two possible use-after-free errors. The dev_dbg() statement at the end of the routine dereferences urb and urb->dev even though both structures may have been deallocated. This patch fixes the problem by storing urb->dev in a local variable (avoiding the dereference of urb) and moving the dev_dbg() up before the usb_put_dev() call. Signed-off-by: Alan Stern Reported-by: Joe Lawrence Tested-by: Joe Lawrence Signed-off-by: Greg Kroah-Hartman Signed-off-by: Ben Hutchings --- drivers/usb/core/hcd.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c index c0ee52a3b9fb..eb2c3bd28db0 100644 --- a/drivers/usb/core/hcd.c +++ b/drivers/usb/core/hcd.c @@ -1542,6 +1542,7 @@ static int unlink1(struct usb_hcd *hcd, struct urb *urb, int status) int usb_hcd_unlink_urb (struct urb *urb, int status) { struct usb_hcd *hcd; + struct usb_device *udev = urb->dev; int retval = -EIDRM; unsigned long flags; @@ -1553,20 +1554,19 @@ int usb_hcd_unlink_urb (struct urb *urb, int status) spin_lock_irqsave(&hcd_urb_unlink_lock, flags); if (atomic_read(&urb->use_count) > 0) { retval = 0; - usb_get_dev(urb->dev); + usb_get_dev(udev); } spin_unlock_irqrestore(&hcd_urb_unlink_lock, flags); if (retval == 0) { hcd = bus_to_hcd(urb->dev->bus); retval = unlink1(hcd, urb, status); - usb_put_dev(urb->dev); + if (retval == 0) + retval = -EINPROGRESS; + else if (retval != -EIDRM && retval != -EBUSY) + dev_dbg(&udev->dev, "hcd_unlink_urb %p fail %d\n", + urb, retval); + usb_put_dev(udev); } - - if (retval == 0) - retval = -EINPROGRESS; - else if (retval != -EIDRM && retval != -EBUSY) - dev_dbg(&urb->dev->dev, "hcd_unlink_urb %p fail %d\n", - urb, retval); return retval; } -- 2.39.2