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=-6.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,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 C1805C43381 for ; Mon, 1 Apr 2019 17:15:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 91ABC20856 for ; Mon, 1 Apr 2019 17:15:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554138929; bh=rTiFpj/8Qx5DZxlRkCe9k3kQ3xDE78/nJy61eI+Wkoc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=gDgGmTfo1rFGkxnZVxqVrTQcPClE4LqDyBd+BLjP5MT+pYspexlEpJT3qIbihaDYx 9s+wgKIAnVvwg/rmn98KbzfwvrM1cy8FsT02U9Eq3PFklvWp1kTxchOyCQcSl3jByp fd5ofOMB7pdMnXb2FFuC/hhhHiPYX+g15KtNb6Io= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730897AbfDARP2 (ORCPT ); Mon, 1 Apr 2019 13:15:28 -0400 Received: from mail.kernel.org ([198.145.29.99]:39542 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729969AbfDARPX (ORCPT ); Mon, 1 Apr 2019 13:15:23 -0400 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 84D2121473; Mon, 1 Apr 2019 17:15:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554138922; bh=rTiFpj/8Qx5DZxlRkCe9k3kQ3xDE78/nJy61eI+Wkoc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Vyuxr4M3/Im7QTkFMp8Y1XfQwolzc+u9/um8drZoQtVVRsDlqzAE139SZhWhrVcDL p+vwaDiIczL3RGN0YBvhpZAp5Gf6jXUZwdPz3ic0nQxsSSnxILClHtEorcHRZIdDij FwdToBHWJM719JSMIMdBmdd+wa6dvneiCvyf4YfY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+d4503ae45b65c5bc1194@syzkaller.appspotmail.com, Takashi Iwai Subject: [PATCH 4.19 059/134] ALSA: pcm: Fix possible OOB access in PCM oss plugins Date: Mon, 1 Apr 2019 19:01:35 +0200 Message-Id: <20190401170050.115818456@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190401170044.243719205@linuxfoundation.org> References: <20190401170044.243719205@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore 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 4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Takashi Iwai commit ca0214ee2802dd47239a4e39fb21c5b00ef61b22 upstream. The PCM OSS emulation converts and transfers the data on the fly via "plugins". The data is converted over the dynamically allocated buffer for each plugin, and recently syzkaller caught OOB in this flow. Although the bisection by syzbot pointed out to the commit 65766ee0bf7f ("ALSA: oss: Use kvzalloc() for local buffer allocations"), this is merely a commit to replace vmalloc() with kvmalloc(), hence it can't be the cause. The further debug action revealed that this happens in the case where a slave PCM doesn't support only the stereo channels while the OSS stream is set up for a mono channel. Below is a brief explanation: At each OSS parameter change, the driver sets up the PCM hw_params again in snd_pcm_oss_change_params_lock(). This is also the place where plugins are created and local buffers are allocated. The problem is that the plugins are created before the final hw_params is determined. Namely, two snd_pcm_hw_param_near() calls for setting the period size and periods may influence on the final result of channels, rates, etc, too, while the current code has already created plugins beforehand with the premature values. So, the plugin believes that channels=1, while the actual I/O is with channels=2, which makes the driver reading/writing over the allocated buffer size. The fix is simply to move the plugin allocation code after the final hw_params call. Reported-by: syzbot+d4503ae45b65c5bc1194@syzkaller.appspotmail.com Cc: Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/core/oss/pcm_oss.c | 43 ++++++++++++++++++++++--------------------- 1 file changed, 22 insertions(+), 21 deletions(-) --- a/sound/core/oss/pcm_oss.c +++ b/sound/core/oss/pcm_oss.c @@ -940,6 +940,28 @@ static int snd_pcm_oss_change_params_loc oss_frame_size = snd_pcm_format_physical_width(params_format(params)) * params_channels(params) / 8; + err = snd_pcm_oss_period_size(substream, params, sparams); + if (err < 0) + goto failure; + + n = snd_pcm_plug_slave_size(substream, runtime->oss.period_bytes / oss_frame_size); + err = snd_pcm_hw_param_near(substream, sparams, SNDRV_PCM_HW_PARAM_PERIOD_SIZE, n, NULL); + if (err < 0) + goto failure; + + err = snd_pcm_hw_param_near(substream, sparams, SNDRV_PCM_HW_PARAM_PERIODS, + runtime->oss.periods, NULL); + if (err < 0) + goto failure; + + snd_pcm_kernel_ioctl(substream, SNDRV_PCM_IOCTL_DROP, NULL); + + err = snd_pcm_kernel_ioctl(substream, SNDRV_PCM_IOCTL_HW_PARAMS, sparams); + if (err < 0) { + pcm_dbg(substream->pcm, "HW_PARAMS failed: %i\n", err); + goto failure; + } + #ifdef CONFIG_SND_PCM_OSS_PLUGINS snd_pcm_oss_plugin_clear(substream); if (!direct) { @@ -974,27 +996,6 @@ static int snd_pcm_oss_change_params_loc } #endif - err = snd_pcm_oss_period_size(substream, params, sparams); - if (err < 0) - goto failure; - - n = snd_pcm_plug_slave_size(substream, runtime->oss.period_bytes / oss_frame_size); - err = snd_pcm_hw_param_near(substream, sparams, SNDRV_PCM_HW_PARAM_PERIOD_SIZE, n, NULL); - if (err < 0) - goto failure; - - err = snd_pcm_hw_param_near(substream, sparams, SNDRV_PCM_HW_PARAM_PERIODS, - runtime->oss.periods, NULL); - if (err < 0) - goto failure; - - snd_pcm_kernel_ioctl(substream, SNDRV_PCM_IOCTL_DROP, NULL); - - if ((err = snd_pcm_kernel_ioctl(substream, SNDRV_PCM_IOCTL_HW_PARAMS, sparams)) < 0) { - pcm_dbg(substream->pcm, "HW_PARAMS failed: %i\n", err); - goto failure; - } - if (runtime->oss.trigger) { sw_params->start_threshold = 1; } else {