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[209.132.180.67]) by mx.google.com with ESMTP id i3si6817257edq.163.2019.10.06.11.24.49; Sun, 06 Oct 2019 11:25:13 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=UprVc3I+; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726826AbfJFSYh (ORCPT + 99 others); Sun, 6 Oct 2019 14:24:37 -0400 Received: from mail.kernel.org ([198.145.29.99]:33028 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726516AbfJFSYg (ORCPT ); Sun, 6 Oct 2019 14:24:36 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0E59420700; Sun, 6 Oct 2019 18:24:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570386275; bh=txN7MuJe7LCPNmbcBl6KP9WG9kKAMumQZHAcbcAhBlE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=UprVc3I+KtdbmOIjUASkc/FwIkdLRjWkCkg++D5j6MuU9FntBFtntacno2O5KioJz 16mAJf47JfYdK+qp1AMnNfdTT1DBcCsLV2tgINkoxKRwhWCtaT+0Ab0FjWhKhg2Uka 6eUbhoyaBxLxVEZENv/MRM2h+xxVFaVdhZJb8vp4= Date: Sun, 6 Oct 2019 20:24:33 +0200 From: Greg Kroah-Hartman To: Todd Kjos , Martijn Coenen Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, syzbot , Mattias Nissler Subject: Re: [PATCH 4.9 30/47] ANDROID: binder: remove waitqueue when thread exits. Message-ID: <20191006182433.GA217738@kroah.com> References: <20191006172016.873463083@linuxfoundation.org> <20191006172018.480360174@linuxfoundation.org> <20191006173202.GA832@sol.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191006173202.GA832@sol.localdomain> User-Agent: Mutt/1.12.2 (2019-09-21) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Oct 06, 2019 at 10:32:02AM -0700, Eric Biggers wrote: > On Sun, Oct 06, 2019 at 07:21:17PM +0200, Greg Kroah-Hartman wrote: > > From: Martijn Coenen > > > > 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 > > Reported-by: syzbot > > Cc: stable # 4.14 > > [backport BINDER_LOOPER_STATE_POLL logic as well] > > Signed-off-by: Mattias Nissler > > Signed-off-by: Greg Kroah-Hartman > > --- > > drivers/android/binder.c | 17 ++++++++++++++++- > > 1 file changed, 16 insertions(+), 1 deletion(-) > > > > --- a/drivers/android/binder.c > > +++ b/drivers/android/binder.c > > @@ -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 { > > @@ -2628,6 +2629,18 @@ static int binder_free_thread(struct bin > > } 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 inner 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); > > @@ -2651,6 +2664,8 @@ static unsigned int binder_poll(struct f > > 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; > > > > Are you sure this backport is correct, given that in 4.9, binder_poll() > sometimes uses proc->wait instead of thread->wait?: > > wait_for_proc_work = thread->transaction_stack == NULL && > list_empty(&thread->todo) && thread->return_error == BR_OK; > > binder_unlock(__func__); > > if (wait_for_proc_work) { > if (binder_has_proc_work(proc, thread)) > return POLLIN; > poll_wait(filp, &proc->wait, wait); > if (binder_has_proc_work(proc, thread)) > return POLLIN; > } else { > if (binder_has_thread_work(thread)) > return POLLIN; > poll_wait(filp, &thread->wait, wait); > if (binder_has_thread_work(thread)) > return POLLIN; > } > return 0; I _think_ the backport is correct, and I know someone has verified that the 4.4.y backport works properly and I don't see much difference here from that version. But I will defer to Todd and Martijn here, as they know this code _WAY_ better than I do. The codebase has changed a lot from 4.9.y to 4.14.y so it makes it hard to do equal comparisons simply. Todd and Martijn, thoughts? thanks, greg k-h