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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E65EFC6FA82 for ; Tue, 13 Sep 2022 15:45:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233704AbiIMPp2 (ORCPT ); Tue, 13 Sep 2022 11:45:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45218 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234609AbiIMPor (ORCPT ); Tue, 13 Sep 2022 11:44:47 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A8B1540555; Tue, 13 Sep 2022 07:48:41 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 3E7C7614EF; Tue, 13 Sep 2022 14:36:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5073DC433D6; Tue, 13 Sep 2022 14:36:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1663079809; bh=+XPBrIOIZ3AEbHVdiyGfUYR8D1RWCPPH5kCaPunTPDE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=oEXoUr7GVMYKlCG8iFevTanV3TAPWuOjl8JFe5z1EHP1Brgp5vIf0PAO6ELPEL717 R7DAv6IAnWru5c0PNviE37HkiRN+AxxdnRXCgnFsV7va6NAkanw5M1EQ8F0LgpoOQ+ zBjz+Iz9/NP//psP+E3aFcP3T8NwoB+IDP3mmZCw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Abhishek Shah , Takashi Iwai Subject: [PATCH 4.9 21/42] ALSA: seq: oss: Fix data-race for max_midi_devs access Date: Tue, 13 Sep 2022 16:07:52 +0200 Message-Id: <20220913140343.344878143@linuxfoundation.org> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20220913140342.228397194@linuxfoundation.org> References: <20220913140342.228397194@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Takashi Iwai commit 22dec134dbfa825b963f8a1807ad19b943e46a56 upstream. ALSA OSS sequencer refers to a global variable max_midi_devs at creating a new port, storing it to its own field. Meanwhile this variable may be changed by other sequencer events at snd_seq_oss_midi_check_exit_port() in parallel, which may cause a data race. OTOH, this data race itself is almost harmless, as the access to the MIDI device is done via get_mdev() and it's protected with a refcount, hence its presence is guaranteed. Though, it's sill better to address the data-race from the code sanity POV, and this patch adds the proper spinlock for the protection. Reported-by: Abhishek Shah Cc: Link: https://lore.kernel.org/r/CAEHB2493pZRXs863w58QWnUTtv3HHfg85aYhLn5HJHCwxqtHQg@mail.gmail.com Link: https://lore.kernel.org/r/20220823072717.1706-1-tiwai@suse.de Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/core/seq/oss/seq_oss_midi.c | 2 ++ 1 file changed, 2 insertions(+) --- a/sound/core/seq/oss/seq_oss_midi.c +++ b/sound/core/seq/oss/seq_oss_midi.c @@ -280,7 +280,9 @@ snd_seq_oss_midi_clear_all(void) void snd_seq_oss_midi_setup(struct seq_oss_devinfo *dp) { + spin_lock_irq(®ister_lock); dp->max_mididev = max_midi_devs; + spin_unlock_irq(®ister_lock); } /*