Re: [PATCH] ANDROID: binder: remove waitqueue when thread exits.

[Greg KH]

On Fri, Jan 05, 2018 at 11:27:07AM +0100, Martijn Coenen wrote:
> binder_poll() passes the thread->wait waitqueue that
> can be slept on for work. When a thread that uses
> epoll explicitly exits using BINDER_THREAD_EXIT,
> the waitqueue is freed, but it is never removed
> from the corresponding epoll data structure. When
> the process subsequently exits, the epoll cleanup
> code tries to access the waitlist, which results in
> a use-after-free.
> 
> Prevent this by using POLLFREE when the thread exits.
> 
> Signed-off-by: Martijn Coenen <maco@xxxxxxxxxxx>
> Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
> ---
>  drivers/android/binder.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)

Should this be a 4.15-final thing, as well as backported to any range of
older kernels?

thanks,

greg k-h