From patchwork Tue Oct 27 13:49:15 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 313109 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 B4020C5517A for ; Tue, 27 Oct 2020 13:58:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7AC69218AC for ; Tue, 27 Oct 2020 13:58:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603807110; bh=Fm8SMGoT1zLCKx2eTQJU65KETB+YjyUzs+tsSf8AAIo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=k2pjFj82YXb7bTqRw5ALoxjmcdOJCrred10eGKylA5GsS2JWLxV8dZP4zgALdG4hU SuLQ6e+axe8FxwJPXIUdGopIMCBbUUcgUP8uA5EJ4SlkfhIiEJllEkjbb5LZxsTTz+ SGF/U5y4Mc81gaUFuEs45rMaoHis8wox0/73XeX8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753095AbgJ0N63 (ORCPT ); Tue, 27 Oct 2020 09:58:29 -0400 Received: from mail.kernel.org ([198.145.29.99]:45758 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753084AbgJ0N63 (ORCPT ); Tue, 27 Oct 2020 09:58:29 -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 C0FCA2068D; Tue, 27 Oct 2020 13:58:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603807108; bh=Fm8SMGoT1zLCKx2eTQJU65KETB+YjyUzs+tsSf8AAIo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=P8dcj1VLUY5TPX+Y/PXLbZNgy8Db6lYCtoG7EFAUrzz1zorcv3XWeCTgPu02xR7eE xP5BuucmNeSWhyQqXpNzfwrRh2OtR68Kr5JmUyTOIHI8PuL0yy62+QB7rpg2IG6jgp udo7Arr0LZeq9w/5Mz9+popYBO2yCpr6Nb4XDe5k= 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 4.4 045/112] ALSA: seq: oss: Avoid mutex lock for a long-time ioctl Date: Tue, 27 Oct 2020 14:49:15 +0100 Message-Id: <20201027134902.692482951@linuxfoundation.org> X-Mailer: git-send-email 2.29.1 In-Reply-To: <20201027134900.532249571@linuxfoundation.org> References: <20201027134900.532249571@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 8044775999eda..4d1548b951c41 100644 --- a/sound/core/seq/oss/seq_oss.c +++ b/sound/core/seq/oss/seq_oss.c @@ -186,9 +186,12 @@ 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; }