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 0BBB3C433FE for ; Mon, 17 Jan 2022 17:00:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241458AbiAQRA2 (ORCPT ); Mon, 17 Jan 2022 12:00:28 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44778 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241454AbiAQQ75 (ORCPT ); Mon, 17 Jan 2022 11:59:57 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 75524C06173E; Mon, 17 Jan 2022 08:59:57 -0800 (PST) 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 1639460EDB; Mon, 17 Jan 2022 16:59:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 90E74C36AEC; Mon, 17 Jan 2022 16:59:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1642438796; bh=vCWM391mahdHAJjL6H0oEHOo3B7sCwqL6vruq8eQ2u4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=sXff+/pw8VO7IZrrkg27mR8fXIqxDuzZ3jNlUetMKS8fvf8x8ECGBEhH4nYuNsxeO lUL9HRDrdTXVex9yj/nT7VQcruXBS2AgMWLj46Hw/G+V3Acpgl8SbgIkWY6U1bC9Kq 5I7ujLEsE5oejZ4qkpTiIBL4gCJRnClyHHKmwlpc/z24dhykVtdPXCK6tDjC1rkt9i cPVbJpSKKwZM+TC/FUBkeJSYGGBRAiYTiZV1SN5liqk9xipWR+ay26coTXZ3c2V3vY fD82q2B6sdr6m6E+fdinIzJPJrNJVrzEI91gJ3YZOq/FOqzgwRS6PwP2NwdZB9+g4I K/IYlOd6+LdNA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Takashi Iwai , Zqiang , syzbot+bb950e68b400ab4f65f8@syzkaller.appspotmail.com, Sasha Levin , perex@perex.cz, tiwai@suse.com, alsa-devel@alsa-project.org Subject: [PATCH AUTOSEL 5.16 25/52] ALSA: seq: Set upper limit of processed events Date: Mon, 17 Jan 2022 11:58:26 -0500 Message-Id: <20220117165853.1470420-25-sashal@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220117165853.1470420-1-sashal@kernel.org> References: <20220117165853.1470420-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Takashi Iwai [ Upstream commit 6fadb494a638d8b8a55864ecc6ac58194f03f327 ] Currently ALSA sequencer core tries to process the queued events as much as possible when they become dispatchable. If applications try to queue too massive events to be processed at the very same timing, the sequencer core would still try to process such all events, either in the interrupt context or via some notifier; in either away, it might be a cause of RCU stall or such problems. As a potential workaround for those problems, this patch adds the upper limit of the amount of events to be processed. The remaining events are processed in the next batch, so they won't be lost. For the time being, it's limited up to 1000 events per queue, which should be high enough for any normal usages. Reported-by: Zqiang Reported-by: syzbot+bb950e68b400ab4f65f8@syzkaller.appspotmail.com Link: https://lore.kernel.org/r/20211102033222.3849-1-qiang.zhang1211@gmail.com Link: https://lore.kernel.org/r/20211207165146.2888-1-tiwai@suse.de Signed-off-by: Takashi Iwai Signed-off-by: Sasha Levin --- sound/core/seq/seq_queue.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/sound/core/seq/seq_queue.c b/sound/core/seq/seq_queue.c index d6c02dea976c8..bc933104c3eea 100644 --- a/sound/core/seq/seq_queue.c +++ b/sound/core/seq/seq_queue.c @@ -235,12 +235,15 @@ struct snd_seq_queue *snd_seq_queue_find_name(char *name) /* -------------------------------------------------------- */ +#define MAX_CELL_PROCESSES_IN_QUEUE 1000 + void snd_seq_check_queue(struct snd_seq_queue *q, int atomic, int hop) { unsigned long flags; struct snd_seq_event_cell *cell; snd_seq_tick_time_t cur_tick; snd_seq_real_time_t cur_time; + int processed = 0; if (q == NULL) return; @@ -263,6 +266,8 @@ void snd_seq_check_queue(struct snd_seq_queue *q, int atomic, int hop) if (!cell) break; snd_seq_dispatch_event(cell, atomic, hop); + if (++processed >= MAX_CELL_PROCESSES_IN_QUEUE) + goto out; /* the rest processed at the next batch */ } /* Process time queue... */ @@ -272,14 +277,19 @@ void snd_seq_check_queue(struct snd_seq_queue *q, int atomic, int hop) if (!cell) break; snd_seq_dispatch_event(cell, atomic, hop); + if (++processed >= MAX_CELL_PROCESSES_IN_QUEUE) + goto out; /* the rest processed at the next batch */ } + out: /* free lock */ spin_lock_irqsave(&q->check_lock, flags); if (q->check_again) { q->check_again = 0; - spin_unlock_irqrestore(&q->check_lock, flags); - goto __again; + if (processed < MAX_CELL_PROCESSES_IN_QUEUE) { + spin_unlock_irqrestore(&q->check_lock, flags); + goto __again; + } } q->check_blocked = 0; spin_unlock_irqrestore(&q->check_lock, flags); -- 2.34.1