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 X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,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 8635DC17441 for ; Mon, 11 Nov 2019 18:40:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5A26921655 for ; Mon, 11 Nov 2019 18:40:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573497650; bh=5shsiuGVpMOzq5flnd+ZIoIzHgqAS7cOLYrX4/j23uI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=oYqzFT2YjrxSyOprF7R/x2et1TeKtusVmsNtsgHad6+Tz4SVrSxdaltK5jByYlUYf z5bwxIR/3Xlw4C8L4cXC0eN2WaIoP8cGbOS4X9ELHX4ArmwPBpU9ZkRws1QPzMZe6x yIaob//SDqSd72e/zPb4irP2/E/AF4lt0dUKMd7w= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728822AbfKKSkt (ORCPT ); Mon, 11 Nov 2019 13:40:49 -0500 Received: from mail.kernel.org ([198.145.29.99]:59934 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727854AbfKKSkp (ORCPT ); Mon, 11 Nov 2019 13:40:45 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 8D3AA21655; Mon, 11 Nov 2019 18:40:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573497645; bh=5shsiuGVpMOzq5flnd+ZIoIzHgqAS7cOLYrX4/j23uI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EKjZ3oXbL/ibvl2nsuaudyGtD2xSJdD3XLsD0mrNYpGECQVJiGl/0C/SyIgFRdbJx fGGXle0kU6KNs2rbvuhuFzZSDXeZcne4HpVez5fKKZcQMm7D2HsCSXvfQuon0x7b3u CJP6JVyutgvbUdpWfbd3tGF81vN1EF3HXLU4OKEE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Takashi Iwai , Tristan Madani Subject: [PATCH 4.19 016/125] ALSA: timer: Fix incorrectly assigned timer instance Date: Mon, 11 Nov 2019 19:27:35 +0100 Message-Id: <20191111181441.922397171@linuxfoundation.org> X-Mailer: git-send-email 2.24.0 In-Reply-To: <20191111181438.945353076@linuxfoundation.org> References: <20191111181438.945353076@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Takashi Iwai commit e7af6307a8a54f0b873960b32b6a644f2d0fbd97 upstream. The clean up commit 41672c0c24a6 ("ALSA: timer: Simplify error path in snd_timer_open()") unified the error handling code paths with the standard goto, but it introduced a subtle bug: the timer instance is stored in snd_timer_open() incorrectly even if it returns an error. This may eventually lead to UAF, as spotted by fuzzer. The culprit is the snd_timer_open() code checks the SNDRV_TIMER_IFLG_EXCLUSIVE flag with the common variable timeri. This variable is supposed to be the newly created instance, but we (ab-)used it for a temporary check before the actual creation of a timer instance. After that point, there is another check for the max number of instances, and it bails out if over the threshold. Before the refactoring above, it worked fine because the code returned directly from that point. After the refactoring, however, it jumps to the unified error path that stores the timeri variable in return -- even if it returns an error. Unfortunately this stored value is kept in the caller side (snd_timer_user_tselect()) in tu->timeri. This causes inconsistency later, as if the timer was successfully assigned. In this patch, we fix it by not re-using timeri variable but a temporary variable for testing the exclusive connection, so timeri remains NULL at that point. Fixes: 41672c0c24a6 ("ALSA: timer: Simplify error path in snd_timer_open()") Reported-and-tested-by: Tristan Madani Cc: Link: https://lore.kernel.org/r/20191106165547.23518-1-tiwai@suse.de Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/core/timer.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -298,11 +298,11 @@ int snd_timer_open(struct snd_timer_inst goto unlock; } if (!list_empty(&timer->open_list_head)) { - timeri = list_entry(timer->open_list_head.next, + struct snd_timer_instance *t = + list_entry(timer->open_list_head.next, struct snd_timer_instance, open_list); - if (timeri->flags & SNDRV_TIMER_IFLG_EXCLUSIVE) { + if (t->flags & SNDRV_TIMER_IFLG_EXCLUSIVE) { err = -EBUSY; - timeri = NULL; goto unlock; } }