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authorMartijn Coenen <maco@android.com>2018-02-16 11:47:15 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-02-16 13:16:38 +0300
commit5eeb2ca02a2f6084fc57ae5c244a38baab07033a (patch)
tree86ee4c41c581810a860fc963293da1bed7724798 /drivers/android/binder.c
parent8ca86f1639ec5890d400fff9211aca22d0a392eb (diff)
downloadlinux-5eeb2ca02a2f6084fc57ae5c244a38baab07033a.tar.xz
ANDROID: binder: synchronize_rcu() when using POLLFREE.
To prevent races with ep_remove_waitqueue() removing the waitqueue at the same time. Reported-by: syzbot+a2a3c4909716e271487e@syzkaller.appspotmail.com Signed-off-by: Martijn Coenen <maco@android.com> Cc: stable <stable@vger.kernel.org> # 4.14+ Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/android/binder.c')
-rw-r--r--drivers/android/binder.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index a85f9033b57e..764b63a5aade 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -4382,6 +4382,15 @@ static int binder_thread_release(struct binder_proc *proc,
binder_inner_proc_unlock(thread->proc);
+ /*
+ * This is needed to avoid races between wake_up_poll() above and
+ * and ep_remove_waitqueue() called for other reasons (eg the epoll file
+ * descriptor being closed); ep_remove_waitqueue() holds an RCU read
+ * lock, so we can be sure it's done after calling synchronize_rcu().
+ */
+ if (thread->looper & BINDER_LOOPER_STATE_POLL)
+ synchronize_rcu();
+
if (send_reply)
binder_send_failed_reply(send_reply, BR_DEAD_REPLY);
binder_release_work(proc, &thread->todo);