From nobody Mon Sep 8 08:44:19 2025 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 0560AC54EE9 for ; Tue, 13 Sep 2022 15:39:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233838AbiIMPjl (ORCPT ); Tue, 13 Sep 2022 11:39:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51230 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236697AbiIMPio (ORCPT ); Tue, 13 Sep 2022 11:38:44 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1A3C22AE9; Tue, 13 Sep 2022 07:44:30 -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 84953614D2; Tue, 13 Sep 2022 14:28:36 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8FB42C433D6; Tue, 13 Sep 2022 14:28:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1663079315; bh=K4dGkykxDeQfgG8iJRdoD0/3YR3v+GjHk/N6AhY71Gw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=RbZJbz9K+lULo5D5zUQEBEuH2m5uKLn4f6Xyl/ZtWGAb9XO/j1clgce4IX2jzqv+3 RgILUdC5J6j+GvDfStMeuFYN3G3jtpVvZ10ropKuGa9g6iSdNH0yzGC629civJVgnP 4Q5RuKRKjsnqzoQyVNoisHULdDPIW9hQK7lgDF/U= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Abhishek Shah , Takashi Iwai Subject: [PATCH 5.4 060/108] ALSA: seq: Fix data-race at module auto-loading Date: Tue, 13 Sep 2022 16:06:31 +0200 Message-Id: <20220913140356.202147261@linuxfoundation.org> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20220913140353.549108748@linuxfoundation.org> References: <20220913140353.549108748@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Takashi Iwai commit 3e7e04b747adea36f349715d9f0998eeebf15d72 upstream. It's been reported that there is a possible data-race accessing to the global card_requested[] array at ALSA sequencer core, which is used for determining whether to call request_module() for the card or not. This data race itself is almost harmless, as it might end up with one extra request_module() call for the already loaded module at most. But it's still better to fix. This patch addresses the possible data race of card_requested[] and client_requested[] arrays by replacing them with bitmask. It's an atomic operation and can work without locks. Reported-by: Abhishek Shah Cc: Link: https://lore.kernel.org/r/CAEHB24_ay6YzARpA1zgCsE7=3DH9CSJJzux618E=3D= Ka4h0YdKn=3DqA@mail.gmail.com Link: https://lore.kernel.org/r/20220823072717.1706-2-tiwai@suse.de Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/core/seq/seq_clientmgr.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) --- a/sound/core/seq/seq_clientmgr.c +++ b/sound/core/seq/seq_clientmgr.c @@ -121,13 +121,13 @@ struct snd_seq_client *snd_seq_client_us spin_unlock_irqrestore(&clients_lock, flags); #ifdef CONFIG_MODULES if (!in_interrupt()) { - static char client_requested[SNDRV_SEQ_GLOBAL_CLIENTS]; - static char card_requested[SNDRV_CARDS]; + static DECLARE_BITMAP(client_requested, SNDRV_SEQ_GLOBAL_CLIENTS); + static DECLARE_BITMAP(card_requested, SNDRV_CARDS); + if (clientid < SNDRV_SEQ_GLOBAL_CLIENTS) { int idx; =09 - if (!client_requested[clientid]) { - client_requested[clientid] =3D 1; + if (!test_and_set_bit(clientid, client_requested)) { for (idx =3D 0; idx < 15; idx++) { if (seq_client_load[idx] < 0) break; @@ -142,10 +142,8 @@ struct snd_seq_client *snd_seq_client_us int card =3D (clientid - SNDRV_SEQ_GLOBAL_CLIENTS) / SNDRV_SEQ_CLIENTS_PER_CARD; if (card < snd_ecards_limit) { - if (! card_requested[card]) { - card_requested[card] =3D 1; + if (!test_and_set_bit(card, card_requested)) snd_request_card(card); - } snd_seq_device_load_drivers(); } }