From patchwork Tue Aug 23 07:27:16 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Takashi Iwai X-Patchwork-Id: 12951804 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 alsa0.perex.cz (alsa0.perex.cz [77.48.224.243]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 91C1DC32774 for ; Tue, 23 Aug 2022 07:28:48 +0000 (UTC) Received: from alsa1.perex.cz (alsa1.perex.cz [207.180.221.201]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by alsa0.perex.cz (Postfix) with ESMTPS id 9A8BB1638; Tue, 23 Aug 2022 09:27:56 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa0.perex.cz 9A8BB1638 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=alsa-project.org; s=default; t=1661239726; bh=+S1F+W8LpGSGfb/dGv+qNixD5KDYZaekjmHNYR4HEac=; h=From:To:Subject:Date:Cc:List-Id:List-Unsubscribe:List-Archive: List-Post:List-Help:List-Subscribe:From; b=RVji9gekHoi3EQob3/Dd/oiV0m4jqVIGwdUk6SwkwEIP6BWse7MrVYA70c5yw23O7 iwbpmWe3JXPG5u0cJakA7zLj0uKL74tVE7GYQXPJO2djBWGrzTOR3kjAuibNzcIKxt aYeB3N4aMUZQMudG626zqnY46e7wbGxio4Pig5bw= Received: from alsa1.perex.cz (localhost.localdomain [127.0.0.1]) by alsa1.perex.cz (Postfix) with ESMTP id ED08CF8030F; Tue, 23 Aug 2022 09:27:29 +0200 (CEST) Received: by alsa1.perex.cz (Postfix, from userid 50401) id 3181EF8020D; Tue, 23 Aug 2022 09:27:27 +0200 (CEST) Received: from smtp-out2.suse.de (smtp-out2.suse.de [IPv6:2001:67c:2178:6::1d]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by alsa1.perex.cz (Postfix) with ESMTPS id 26430F800A7 for ; Tue, 23 Aug 2022 09:27:19 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa1.perex.cz 26430F800A7 Authentication-Results: alsa1.perex.cz; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.b="e/F2nVTc"; dkim=permerror (0-bit key) header.d=suse.de header.i=@suse.de header.b="k4R5sjUE" Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 555AF20EAE; Tue, 23 Aug 2022 07:27:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1661239639; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=u+Vc+16iGhYLLsyieitjMYPGvpybqeJY2ZKKhBjouVw=; b=e/F2nVTcJQIAgxSBCPkoe+KleufrgC50Qd8LfQZ/bl9ROCr0pbIHHx+22GEk8eWI52G12z oAaXMOD+OImtCbspeP1+lDazS66E3t5fBR9QqMsJYafBQqHdFdD8XHHKS5mJIefwOJtfsb 1rebfiog8XhgIe5N8wQBQ0nzGNEmsN0= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1661239639; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=u+Vc+16iGhYLLsyieitjMYPGvpybqeJY2ZKKhBjouVw=; b=k4R5sjUEYdkeM3E4STCris9Xr3D0k/0qcMXoNw7FqEmYhLtqgGpUHHkq9xa2GBBjPUPQY3 JKZEAWIa2eQqnuCA== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 29CBA13AB7; Tue, 23 Aug 2022 07:27:19 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id fO80CVeBBGOUPAAAMHmgww (envelope-from ); Tue, 23 Aug 2022 07:27:19 +0000 From: Takashi Iwai To: alsa-devel@alsa-project.org Subject: [PATCH 1/2] ALSA: seq: oss: Fix data-race for max_midi_devs access Date: Tue, 23 Aug 2022 09:27:16 +0200 Message-Id: <20220823072717.1706-1-tiwai@suse.de> X-Mailer: git-send-email 2.35.3 MIME-Version: 1.0 Cc: Abhishek Shah , Gabriel Ryan X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: "Alsa-devel" 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 Signed-off-by: Takashi Iwai --- sound/core/seq/oss/seq_oss_midi.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/sound/core/seq/oss/seq_oss_midi.c b/sound/core/seq/oss/seq_oss_midi.c index 1e3bf086f867..07efb38f58ac 100644 --- a/sound/core/seq/oss/seq_oss_midi.c +++ b/sound/core/seq/oss/seq_oss_midi.c @@ -270,7 +270,9 @@ 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); } /*