| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.18 107/151] USB: fix use-after-free bug in usb_hcd_unlink_urb() | Date | Tue, 3 Mar 2015 22:14:01 -0800 |
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3.18-stable review patch. If anyone has any objections, please let me know.
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From: Alan Stern <stern@rowland.harvard.edu>
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 <stern@rowland.harvard.edu> Reported-by: Joe Lawrence <joe.lawrence@stratus.com> Tested-by: Joe Lawrence <joe.lawrence@stratus.com> Signed-off-by: Greg Kroah-Hartman <greg@kroah.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/usb/core/hcd.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-)
--- a/drivers/usb/core/hcd.c +++ b/drivers/usb/core/hcd.c @@ -1618,6 +1618,7 @@ static int unlink1(struct usb_hcd *hcd, 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; @@ -1629,20 +1630,19 @@ int usb_hcd_unlink_urb (struct urb *urb, 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; }
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