Re: [PATCH] r8a66597: Fix a possible concurrency use-after-free bug in r8a66597_endpoint_disable()
From: Greg KH
Date: Tue Dec 18 2018 - 06:11:55 EST
On Tue, Dec 18, 2018 at 06:00:20PM +0800, Jia-Ju Bai wrote:
> 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:
> kfree(hep->hcpriv) (line 1995 in Linux-4.19)
> This variable is read by r8a66597_urb_enqueue() via the call path:
> 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 <baijiaju1990@xxxxxxxxx>
> 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,
> 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?
Otherwise this seems to look good to me.