From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752297Ab2AHOC7 (ORCPT ); Sun, 8 Jan 2012 09:02:59 -0500 Received: from mail-iy0-f174.google.com ([209.85.210.174]:56947 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750917Ab2AHOC5 (ORCPT ); Sun, 8 Jan 2012 09:02:57 -0500 Message-ID: <4F09A20C.7090705@gmail.com> Date: Sun, 08 Jan 2012 09:02:52 -0500 From: Xi Wang User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:8.0) Gecko/20111105 Thunderbird/8.0 MIME-Version: 1.0 To: Takashi Iwai , Jaroslav Kysela , Clemens Ladisch , Daniel Mack , Wolfgang Breyha CC: alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org, Xi Wang Subject: [PATCH v2] ALSA: usb-audio: fix possible hang and overflow in parse_uac2_sample_rate_range() References: <1325698749-5353-1-git-send-email-xi.wang@gmail.com> In-Reply-To: <1325698749-5353-1-git-send-email-xi.wang@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org A malicious USB device may feed in carefully crafted min/max/res values, so that the inner loop in parse_uac2_sample_rate_range() could run for a long time or even never terminate, e.g., given max = INT_MAX. Also nr_rates could be a large integer, which causes an integer overflow in the subsequent call to kmalloc() in parse_audio_format_rates_v2(). Thus, kmalloc() would allocate a smaller buffer than expected, leading to a memory corruption. To exploit the two vulnerabilities, an attacker needs physical access to the machine to plug in a malicious USB device. This patch makes two changes. 1) The type of "rate" is changed to unsigned int, so that the loop could stop once "rate" is larger than INT_MAX. 2) Limit nr_rates to 1024. Suggested-by: Takashi Iwai Signed-off-by: Xi Wang --- sound/usb/format.c | 8 +++++++- 1 files changed, 7 insertions(+), 1 deletions(-) diff --git a/sound/usb/format.c b/sound/usb/format.c index 89421d1..e09aba1 100644 --- a/sound/usb/format.c +++ b/sound/usb/format.c @@ -209,6 +209,8 @@ static int parse_audio_format_rates_v1(struct snd_usb_audio *chip, struct audiof return 0; } +#define MAX_UAC2_NR_RATES 1024 + /* * Helper function to walk the array of sample rate triplets reported by * the device. The problem is that we need to parse whole array first to @@ -226,7 +228,7 @@ static int parse_uac2_sample_rate_range(struct audioformat *fp, int nr_triplets, int min = combine_quad(&data[2 + 12 * i]); int max = combine_quad(&data[6 + 12 * i]); int res = combine_quad(&data[10 + 12 * i]); - int rate; + unsigned int rate; if ((max < 0) || (min < 0) || (res < 0) || (max < min)) continue; @@ -253,6 +255,10 @@ static int parse_uac2_sample_rate_range(struct audioformat *fp, int nr_triplets, fp->rates |= snd_pcm_rate_to_rate_bit(rate); nr_rates++; + if (nr_rates >= MAX_UAC2_NR_RATES) { + snd_printk(KERN_ERR "invalid uac2 rates\n"); + break; + } /* avoid endless loop */ if (res == 0) -- 1.7.5.4