From patchwork Tue Oct 27 13:51:40 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 307079 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8628BC388F9 for ; Tue, 27 Oct 2020 17:37:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2712E20878 for ; Tue, 27 Oct 2020 17:37:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603820231; bh=1NVx5rLyal8hpuvHe85OB/FAzDsAwKW3xaNGwbHZY2E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=mOS2p4YATJV/GL7ORNS6jq+XQIVwzo+MZ1W7FJE1X/E7jDdTMvaol88RKMiPjJxlM eFfI/F0i9gsEOil/86Q1gWaEEI4iea7CeuNaIPvcJy7to33VCZaOB0HxZEp1LIYrQY Yb9dKMfCmmCEjSB4HrjzZsDywfxoUjbABWfRf+tE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1820667AbgJ0RhK (ORCPT ); Tue, 27 Oct 2020 13:37:10 -0400 Received: from mail.kernel.org ([198.145.29.99]:34478 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760653AbgJ0Ofm (ORCPT ); Tue, 27 Oct 2020 10:35:42 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (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 4617B22202; Tue, 27 Oct 2020 14:35:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603809340; bh=1NVx5rLyal8hpuvHe85OB/FAzDsAwKW3xaNGwbHZY2E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zNwnW+XjKvrEMpdVxtJc+4qSZhZKWM7nFFatEY2aCsEeNpz24v8VWTxOSpTAUw/cl jSghJACd9vyF8UCK0GDKN868cKk8qCPO+3CHXVjIhbkd2vumoq1Lha7FfvwoI8Pgp0 TjVGqjCZot7/koJDkUYaPxhOfcNG0z/+YPi1yq8Y= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Pavel Machek , Takashi Iwai , Sasha Levin Subject: [PATCH 5.4 162/408] ALSA: seq: oss: Avoid mutex lock for a long-time ioctl Date: Tue, 27 Oct 2020 14:51:40 +0100 Message-Id: <20201027135502.611856996@linuxfoundation.org> X-Mailer: git-send-email 2.29.1 In-Reply-To: <20201027135455.027547757@linuxfoundation.org> References: <20201027135455.027547757@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Takashi Iwai [ Upstream commit 2759caad2600d503c3b0ed800e7e03d2cd7a4c05 ] Recently we applied a fix to cover the whole OSS sequencer ioctls with the mutex for dealing with the possible races. This works fine in general, but in theory, this may lead to unexpectedly long stall if an ioctl like SNDCTL_SEQ_SYNC is issued and an event with the far future timestamp was queued. For fixing such a potential stall, this patch changes the mutex lock applied conditionally excluding such an ioctl command. Also, change the mutex_lock() with the interruptible version for user to allow escaping from the big-hammer mutex. Fixes: 80982c7e834e ("ALSA: seq: oss: Serialize ioctls") Suggested-by: Pavel Machek Link: https://lore.kernel.org/r/20200922083856.28572-1-tiwai@suse.de Signed-off-by: Takashi Iwai Signed-off-by: Sasha Levin --- sound/core/seq/oss/seq_oss.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/sound/core/seq/oss/seq_oss.c b/sound/core/seq/oss/seq_oss.c index c8b9c0b315d8f..250a92b187265 100644 --- a/sound/core/seq/oss/seq_oss.c +++ b/sound/core/seq/oss/seq_oss.c @@ -174,9 +174,12 @@ odev_ioctl(struct file *file, unsigned int cmd, unsigned long arg) if (snd_BUG_ON(!dp)) return -ENXIO; - mutex_lock(®ister_mutex); + if (cmd != SNDCTL_SEQ_SYNC && + mutex_lock_interruptible(®ister_mutex)) + return -ERESTARTSYS; rc = snd_seq_oss_ioctl(dp, cmd, arg); - mutex_unlock(®ister_mutex); + if (cmd != SNDCTL_SEQ_SYNC) + mutex_unlock(®ister_mutex); return rc; }