On 2018/12/18 19:11, Greg KH wrote:

On Tue, Dec 18, 2018 at 06:00:20PM +0800, Jia-Ju Bai wrote:

quoted

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: Jia-Ju Bai <redacted>
---
  drivers/usb/host/r8a66597-hcd.c | 3 ++-
  1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/host/r8a66597-hcd.c b/drivers/usb/host/r8a66597-hcd.c
index 984892dd72f5..1495ce14ad22 100644
--- a/drivers/usb/host/r8a66597-hcd.c
+++ b/drivers/usb/host/r8a66597-hcd.c

@@ -1991,13 +1991,14 @@ static void r8a66597_endpoint_disable(struct usb_hcd *hcd,
  		return;
  	pipenum = pipe->info.pipenum;
  
+	spin_lock_irqsave(&r8a66597->lock, flags);

Don't you also need the __aquires/__releases markings on this function
in order to properly annotate it, like the rest of the driver has?

Okay, thanks for this suggestion :)
I will send a v2 patch.


Best wishes,
Jia-Ju Bai