[PATCH 3.4 018/172] USB: fix use-after-free bug in usb_hcd_unlink_urb()

lizf
2015-06-16T08:40:06Z

From: Alan Stern <stern@rowland.harvard.edu>

3.4.108-rc1 review patch. If anyone has any objections, please let me know.

------------------

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: Zefan Li <lizefan@huawei.com>
---
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 6baeada..f1d0e3c 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -1528,6 +1528,7 @@ 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;

@@ -1539,20 +1540,19 @@ 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;
}

--
1.9.1