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authorMartijn Coenen <maco@android.com>2018-01-05 11:27:07 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-02-03 17:39:22 +0100
commit7a3cee43e935b9d526ad07f20bf005ba7e74d05b (patch)
parent2ba5966eddefdf04306bd1da36811c8b83a9664d (diff)
ANDROID: binder: remove waitqueue when thread exits.
commit f5cb779ba16334b45ba8946d6bfa6d9834d1527f upstream. 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@android.com> Reported-by: syzbot <syzkaller@googlegroups.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 12 insertions, 0 deletions
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index a340766b51fe..2ef8bd29e188 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -4302,6 +4302,18 @@ static int binder_thread_release(struct binder_proc *proc,
if (t)
+ /*
+ * If this thread used poll, make sure we remove the waitqueue
+ * from any epoll data structures holding it with POLLFREE.
+ * waitqueue_active() is safe to use here because we're holding
+ * the inner lock.
+ */
+ if ((thread->looper & BINDER_LOOPER_STATE_POLL) &&
+ waitqueue_active(&thread->wait)) {
+ wake_up_poll(&thread->wait, POLLHUP | POLLFREE);
+ }
if (send_reply)