From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933459AbdCJOkz (ORCPT ); Fri, 10 Mar 2017 09:40:55 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:35598 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755341AbdCJJLd (ORCPT ); Fri, 10 Mar 2017 04:11:33 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dmitry Vyukov , Takashi Iwai Subject: [PATCH 4.4 19/91] ALSA: timer: Reject user params with too small ticks Date: Fri, 10 Mar 2017 10:08:18 +0100 Message-Id: <20170310083901.722613970@linuxfoundation.org> X-Mailer: git-send-email 2.12.0 In-Reply-To: <20170310083900.730556986@linuxfoundation.org> References: <20170310083900.730556986@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Takashi Iwai commit 71321eb3f2d0df4e6c327e0b936eec4458a12054 upstream. When a user sets a too small ticks with a fine-grained timer like hrtimer, the kernel tries to fire up the timer irq too frequently. This may lead to the condensed locks, eventually the kernel spinlock lockup with warnings. For avoiding such a situation, we define a lower limit of the resolution, namely 1ms. When the user passes a too small tick value that results in less than that, the kernel returns -EINVAL now. Reported-by: Dmitry Vyukov Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/core/timer.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -1700,9 +1700,21 @@ static int snd_timer_user_params(struct return -EBADFD; if (copy_from_user(¶ms, _params, sizeof(params))) return -EFAULT; - if (!(t->hw.flags & SNDRV_TIMER_HW_SLAVE) && params.ticks < 1) { - err = -EINVAL; - goto _end; + if (!(t->hw.flags & SNDRV_TIMER_HW_SLAVE)) { + u64 resolution; + + if (params.ticks < 1) { + err = -EINVAL; + goto _end; + } + + /* Don't allow resolution less than 1ms */ + resolution = snd_timer_resolution(tu->timeri); + resolution *= params.ticks; + if (resolution < 1000000) { + err = -EINVAL; + goto _end; + } } if (params.queue_size > 0 && (params.queue_size < 32 || params.queue_size > 1024)) {