From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail4.comsite.net (mail4.comsite.net [205.238.176.238]) by ozlabs.org (Postfix) with ESMTP id 2BDB01007D1 for ; Fri, 25 Mar 2011 02:14:41 +1100 (EST) From: Milton Miller Message-id: Subject: Re: hvc_console: Don't access hvc_task if not initialised To: Amit Shah References: In-Reply-To: Date: Thu, 24 Mar 2011 08:58:04 -0600 Cc: Rusty Russell , linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, greg@kroah.com, Amit Shah List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , [removed stable list from discussion] On Thu, 24 Mar 2011 07:29:58 -0000, Amit Shah wrote: > hvc_open() can be called without having any backing device. This > results in a call to hvc_kick() which calls wake_up_process on a NULL > pointer. How is hvc_open called without a hvc_driver registered to the tty layer? > Ensure hvc is initialised by checking for a non-NULL hvc_task > before waking up the hvc thread. No if the task is missing the subsystem is really stuck. Put a check in open and refuse to open. > > This was found by an autotest run for virtio_console without having a > console backend. > stack trace please > CC: stable@kernel.org > Signed-off-by: Amit Shah > > --- > drivers/tty/hvc/hvc_console.c | 3 +++ > 1 files changed, 3 insertions(+), 0 deletions(-) > > diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c > index e9cba13..b2cb5cc 100644 > --- a/drivers/tty/hvc/hvc_console.c > +++ b/drivers/tty/hvc/hvc_console.c > @@ -286,6 +286,9 @@ EXPORT_SYMBOL_GPL(hvc_instantiate); > /* Wake the sleeping khvcd */ > void hvc_kick(void) > { > + if (!hvc_task) > + return; > + > hvc_kicked = 1; > wake_up_process(hvc_task); > }