From patchwork Tue Oct 27 13:50:05 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 307200 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 CB669C4363A for ; Tue, 27 Oct 2020 17:13:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7753120657 for ; Tue, 27 Oct 2020 17:13:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603818783; bh=1NVx5rLyal8hpuvHe85OB/FAzDsAwKW3xaNGwbHZY2E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=uVAuUMpFEvjBZflGHgTa4coFRMwcRaHfbeIkV+GSNb7mum0vFGfk9tuuUjEOC5jeB oHpxmuwU2Kdnxc04yg7LaSIBQ9Xi7w1Ifo/P2CavyHEyeoVWmMSOokmAxQLFIDsufL +XniL/ZNf7b7n7fUKZ5fbRsuu0xR3CxYnJxc1yoU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1817073AbgJ0RNA (ORCPT ); Tue, 27 Oct 2020 13:13:00 -0400 Received: from mail.kernel.org ([198.145.29.99]:33106 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1784760AbgJ0O7l (ORCPT ); Tue, 27 Oct 2020 10:59:41 -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 3E08D20715; Tue, 27 Oct 2020 14:59:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603810781; bh=1NVx5rLyal8hpuvHe85OB/FAzDsAwKW3xaNGwbHZY2E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ie2XN2KEsiJSCUGCPPCUvKagEgme2VIR+9/i83YwjqYmzBFpYdsNX30mqKanQL8Sw KqqGG4/n6f/U14Z7084DSJv6WrPXdYBqsPLTrQaiZ5GFPdv9YFsWyDZihQ/l+HN9jg fUKjA5eY2uKh3tdI1DIX3qzi/nGDFRUrdyI9DuXs= 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 5.8 262/633] ALSA: seq: oss: Avoid mutex lock for a long-time ioctl Date: Tue, 27 Oct 2020 14:50:05 +0100 Message-Id: <20201027135534.953936199@linuxfoundation.org> X-Mailer: git-send-email 2.29.1 In-Reply-To: <20201027135522.655719020@linuxfoundation.org> References: <20201027135522.655719020@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; }