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ANDROID: binder: remove waitqueue when thread exits.

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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>
Cc: stable <stable@vger.kernel.org> # 4.14
[backport BINDER_LOOPER_STATE_POLL logic as well]
Signed-off-by: Mattias Nissler <mnissler@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Martijn Coenen 2018-01-05 11:27:07 +01:00 committed by Greg Kroah-Hartman
parent 9add3e08a8
commit 80eb98a4ee
1 changed files with 16 additions and 1 deletions
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17
drivers/android/binder.c
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@ -334,7 +334,8 @@ enum {
BINDER_LOOPER_STATE_EXITED = 0x04,
BINDER_LOOPER_STATE_INVALID = 0x08,
BINDER_LOOPER_STATE_WAITING = 0x10,
BINDER_LOOPER_STATE_NEED_RETURN = 0x20
BINDER_LOOPER_STATE_NEED_RETURN = 0x20,
BINDER_LOOPER_STATE_POLL = 0x40,
};
struct binder_thread {
@ -2610,6 +2611,18 @@ static int binder_free_thread(struct binder_proc *proc,
} else
BUG();
}
/*
* 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 global lock.
*/
if ((thread->looper & BINDER_LOOPER_STATE_POLL) &&
waitqueue_active(&thread->wait)) {
wake_up_poll(&thread->wait, POLLHUP | POLLFREE);
}
if (send_reply)
binder_send_failed_reply(send_reply, BR_DEAD_REPLY);
binder_release_work(&thread->todo);
@ -2633,6 +2646,8 @@ static unsigned int binder_poll(struct file *filp,
return POLLERR;
}
thread->looper |= BINDER_LOOPER_STATE_POLL;
wait_for_proc_work = thread->transaction_stack == NULL &&
list_empty(&thread->todo) && thread->return_error == BR_OK;