From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753380Ab1AEXGn (ORCPT ); Wed, 5 Jan 2011 18:06:43 -0500 Received: from kroah.org ([198.145.64.141]:50842 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753347Ab1AEXGj (ORCPT ); Wed, 5 Jan 2011 18:06:39 -0500 X-Mailbox-Line: From gregkh@clark.site Wed Jan 5 15:03:26 2011 Message-Id: <20110105230326.581569920@clark.site> User-Agent: quilt/0.48-11.2 Date: Wed, 05 Jan 2011 15:00:49 -0800 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Anton Blanchard , Amit Shah , Rusty Russell Subject: [31/49] hvc_console: Fix race between hvc_close and hvc_remove, again In-Reply-To: <20110105230438.GA26241@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.32-longterm review patch. If anyone has any objections, please let us know. ------------------ From: Anton Blanchard commit 320718ee074acce5ffced6506cb51af1388942aa upstream. I don't claim to understand the tty layer, but it seems like hvc_open and hvc_close should be balanced in their kref reference counting. Right now we get a kref every call to hvc_open: if (hp->count++ > 0) { tty_kref_get(tty); <----- here spin_unlock_irqrestore(&hp->lock, flags); hvc_kick(); return 0; } /* else count == 0 */ tty->driver_data = hp; hp->tty = tty_kref_get(tty); <------ or here if hp->count was 0 But hvc_close has: tty_kref_get(tty); if (--hp->count == 0) { ... /* Put the ref obtained in hvc_open() */ tty_kref_put(tty); ... } tty_kref_put(tty); Since the outside kref get/put balance we only do a single kref_put when count reaches 0. The patch below changes things to call tty_kref_put once for every hvc_close call, and with that my machine boots fine. Signed-off-by: Anton Blanchard Acked-by: Amit Shah Signed-off-by: Rusty Russell Signed-off-by: Greg Kroah-Hartman --- drivers/char/hvc_console.c | 4 ---- 1 file changed, 4 deletions(-) --- a/drivers/char/hvc_console.c +++ b/drivers/char/hvc_console.c @@ -367,16 +367,12 @@ static void hvc_close(struct tty_struct hp = tty->driver_data; spin_lock_irqsave(&hp->lock, flags); - tty_kref_get(tty); if (--hp->count == 0) { /* We are done with the tty pointer now. */ hp->tty = NULL; spin_unlock_irqrestore(&hp->lock, flags); - /* Put the ref obtained in hvc_open() */ - tty_kref_put(tty); - if (hp->ops->notifier_del) hp->ops->notifier_del(hp, hp->data);