Re: [PATCH 4.14] can: bcm: fix UAF of bcm op

[Greg KH <gregkh@linuxfoundation.org>]

On Sat, Jan 22, 2022 at 06:25:06PM +0800, Ziyang Xuan wrote:
> Stopping tasklet and hrtimer rely on the active state of tasklet and
> hrtimer sequentially in bcm_remove_op(), the op object will be freed
> if they are all unactive. Assume the hrtimer timeout is short, the
> hrtimer cb has been excuted after tasklet conditional judgment which
> must be false after last round tasklet_kill() and before condition
> hrtimer_active(), it is false when execute to hrtimer_active(). Bug
> is triggerd, because the stopping action is end and the op object
> will be freed, but the tasklet is scheduled. The resources of the op
> object will occur UAF bug.
> 
> Move hrtimer_cancel() behind tasklet_kill() and switch 'while () {...}'
> to 'do {...} while ()' to fix the op UAF problem.
> 
> Fixes: a06393ed0316 ("can: bcm: fix hrtimer/tasklet termination in bcm op removal")
> Reported-by: syzbot+5ca851459ed04c778d1d@syzkaller.appspotmail.com
> Cc: stable@vger.kernel.org
> Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
> ---
>  net/can/bcm.c | 20 ++++++++++----------
>  1 file changed, 10 insertions(+), 10 deletions(-)

What is the git commit id of this change in Linus's tree?

thanks,

greg k-h