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Commit a5d6edaa authored by Jia-Ju Bai's avatar Jia-Ju Bai Committed by Greg Kroah-Hartman
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usb: r8a66597: Fix a possible concurrency use-after-free bug in r8a66597_endpoint_disable() 



commit c85400f886e3d41e69966470879f635a2b50084c upstream.

The function r8a66597_endpoint_disable() and r8a66597_urb_enqueue() may
be concurrently executed.
The two functions both access a possible shared variable "hep->hcpriv".

This shared variable is freed by r8a66597_endpoint_disable() via the
call path:
r8a66597_endpoint_disable
  kfree(hep->hcpriv) (line 1995 in Linux-4.19)

This variable is read by r8a66597_urb_enqueue() via the call path:
r8a66597_urb_enqueue
  spin_lock_irqsave(&r8a66597->lock)
  init_pipe_info
    enable_r8a66597_pipe
      pipe = hep->hcpriv (line 802 in Linux-4.19)

The read operation is protected by a spinlock, but the free operation
is not protected by this spinlock, thus a concurrency use-after-free bug
may occur.

To fix this bug, the spin-lock and spin-unlock function calls in
r8a66597_endpoint_disable() are moved to protect the free operation.

Signed-off-by: default avatarJia-Ju Bai <baijiaju1990@gmail.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent bef58542

drivers/usb/host/r8a66597-hcd.c

+4 −1
Original line number Diff line number Diff line
@@ -1990,6 +1990,8 @@ static int r8a66597_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, 


static void r8a66597_endpoint_disable(struct usb_hcd *hcd,

				      struct usb_host_endpoint *hep)

__acquires(r8a66597->lock)

__releases(r8a66597->lock)

{

	struct r8a66597 *r8a66597 = hcd_to_r8a66597(hcd);

	struct r8a66597_pipe *pipe = (struct r8a66597_pipe *)hep->hcpriv;
@@ -2002,13 +2004,14 @@ static void r8a66597_endpoint_disable(struct usb_hcd *hcd, 
		return;

	pipenum = pipe->info.pipenum;



	spin_lock_irqsave(&r8a66597->lock, flags);

	if (pipenum == 0) {

		kfree(hep->hcpriv);

		hep->hcpriv = NULL;

		spin_unlock_irqrestore(&r8a66597->lock, flags);

		return;

	}



	spin_lock_irqsave(&r8a66597->lock, flags);

	pipe_stop(r8a66597, pipe);

	pipe_irq_disable(r8a66597, pipenum);

	disable_irq_empty(r8a66597, pipenum);