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[209.132.180.67]) by mx.google.com with ESMTP id n14si7513902edv.377.2019.10.07.02.38.38; Mon, 07 Oct 2019 02:39:03 -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=xhb9NYnl; 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 S1727345AbfJGJiY (ORCPT + 99 others); Mon, 7 Oct 2019 05:38:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:58250 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726010AbfJGJiY (ORCPT ); Mon, 7 Oct 2019 05:38:24 -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 51B1C21655; Mon, 7 Oct 2019 09:38:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570441101; bh=3zhwfHIcLxbbQ+KpMXuhI+igbeHR1uDpFIhjOQRNKws=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=xhb9NYnljNV1xaVQoNXkMjTFv8xFVwvlhvXK4T26Gs97v9UHxKRdpu+nh7lconEFf LaCA52oK2CY9iuiQSync4Amm0bhSZeC0dviaQ3ejyxtBkyzHUoF8aKDt+3Ed3clXCW TS3MgAFsmDHpRMFHKaLl8QSae5HIAOztyxbzJvYY= Date: Mon, 7 Oct 2019 11:38:19 +0200 From: Greg Kroah-Hartman To: Martijn Coenen Cc: LKML , stable@vger.kernel.org, syzbot , Mattias Nissler Subject: Re: [PATCH 4.9 30/47] ANDROID: binder: remove waitqueue when thread exits. Message-ID: <20191007093819.GA84909@kroah.com> References: <20191006172016.873463083@linuxfoundation.org> <20191006172018.480360174@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Mon, Oct 07, 2019 at 11:33:53AM +0200, Martijn Coenen wrote: > On Sun, Oct 6, 2019 at 7:23 PM 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. > > This should be "global lock" in 4.9 and 4.4 :) I'll go update the comment now, thanks! > Otherwise LGTM, thanks! thanks for the review. greg k-h