From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932147Ab3FPWb5 (ORCPT ); Sun, 16 Jun 2013 18:31:57 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:46288 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755463Ab3FPWIn (ORCPT ); Sun, 16 Jun 2013 18:08:43 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Xi Wang" , "Takashi Iwai" Date: Sun, 16 Jun 2013 23:01:37 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [13/83] ALSA: usb-audio: fix possible hang and overflow in parse_uac2_sample_rate_range() In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.101 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.47-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Xi Wang commit 4fa0e81b83503900be277e6273a79651b375e288 upstream. 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 Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings --- sound/usb/format.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) 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)