From mboxrd@z Thu Jan 1 00:00:00 1970 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=unavailable 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 92338C388F9 for ; Tue, 27 Oct 2020 17:37:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4C68D21D24 for ; Tue, 27 Oct 2020 17:37:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603820240; bh=1NVx5rLyal8hpuvHe85OB/FAzDsAwKW3xaNGwbHZY2E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=BsGaps+P94zlikNCsYXll+bJ82WaTVA3wfp36u1tcXGB43Gf49bFmNPnBzNBJ4js6 vMBVn0HHcQ95ucQjxK9DGDx52mYZs+sgsp/YVzfHwXk+FVEdi82S7af0zUwA95tDr5 oSw6oTqmSchFCSRQBLFIxPxbKrKd0rtlak714+M0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1820688AbgJ0RhO (ORCPT ); Tue, 27 Oct 2020 13:37:14 -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 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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; } -- 2.25.1