Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753806AbdFLPcI (ORCPT ); Mon, 12 Jun 2017 11:32:08 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:40552 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753775AbdFLPcF (ORCPT ); Mon, 12 Jun 2017 11:32:05 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Alexander Potapenko , Takashi Iwai Subject: [PATCH 4.11 134/150] ALSA: timer: Fix race between read and ioctl Date: Mon, 12 Jun 2017 17:25:41 +0200 Message-Id: <20170612152525.609420916@linuxfoundation.org> X-Mailer: git-send-email 2.13.1 In-Reply-To: <20170612152519.404936272@linuxfoundation.org> References: <20170612152519.404936272@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 Content-Length: 2302 Lines: 73 4.11-stable review patch. If anyone has any objections, please let me know. ------------------ From: Takashi Iwai commit d11662f4f798b50d8c8743f433842c3e40fe3378 upstream. The read from ALSA timer device, the function snd_timer_user_tread(), may access to an uninitialized struct snd_timer_user fields when the read is concurrently performed while the ioctl like snd_timer_user_tselect() is invoked. We have already fixed the races among ioctls via a mutex, but we seem to have forgotten the race between read vs ioctl. This patch simply applies (more exactly extends the already applied range of) tu->ioctl_lock in snd_timer_user_tread() for closing the race window. Reported-by: Alexander Potapenko Tested-by: Alexander Potapenko Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/core/timer.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -1964,6 +1964,7 @@ static ssize_t snd_timer_user_read(struc tu = file->private_data; unit = tu->tread ? sizeof(struct snd_timer_tread) : sizeof(struct snd_timer_read); + mutex_lock(&tu->ioctl_lock); spin_lock_irq(&tu->qlock); while ((long)count - result >= unit) { while (!tu->qused) { @@ -1979,7 +1980,9 @@ static ssize_t snd_timer_user_read(struc add_wait_queue(&tu->qchange_sleep, &wait); spin_unlock_irq(&tu->qlock); + mutex_unlock(&tu->ioctl_lock); schedule(); + mutex_lock(&tu->ioctl_lock); spin_lock_irq(&tu->qlock); remove_wait_queue(&tu->qchange_sleep, &wait); @@ -1999,7 +2002,6 @@ static ssize_t snd_timer_user_read(struc tu->qused--; spin_unlock_irq(&tu->qlock); - mutex_lock(&tu->ioctl_lock); if (tu->tread) { if (copy_to_user(buffer, &tu->tqueue[qhead], sizeof(struct snd_timer_tread))) @@ -2009,7 +2011,6 @@ static ssize_t snd_timer_user_read(struc sizeof(struct snd_timer_read))) err = -EFAULT; } - mutex_unlock(&tu->ioctl_lock); spin_lock_irq(&tu->qlock); if (err < 0) @@ -2019,6 +2020,7 @@ static ssize_t snd_timer_user_read(struc } _error: spin_unlock_irq(&tu->qlock); + mutex_unlock(&tu->ioctl_lock); return result > 0 ? result : err; }