tree bc2bd6230ae9e76e859e3724a2751de941db5742
parent b30d2b5deba5c198db738318cc32d23f515bb80e
author Martijn Coenen <maco@android.com> 1515148027 +0100
committer Martijn Coenen <maco@google.com> 1517918501 +0000

UPSTREAM: ANDROID: binder: remove waitqueue when thread exits.

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.

(cherry picked from commit f5cb779ba16334b45ba8946d6bfa6d9834d1527f)

Change-Id: Ib34b1cbb8ab2192d78c3d9956b2f963a66ecad2e
Signed-off-by: Martijn Coenen <maco@android.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: stable <stable@vger.kernel.org> # 4.14
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>