From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756567Ab2ADRk6 (ORCPT ); Wed, 4 Jan 2012 12:40:58 -0500 Received: from mail-qy0-f174.google.com ([209.85.216.174]:45329 "EHLO mail-qy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751875Ab2ADRk5 (ORCPT ); Wed, 4 Jan 2012 12:40:57 -0500 From: Xi Wang To: Jaroslav Kysela , Takashi Iwai , Clemens Ladisch , Daniel Mack , Wolfgang Breyha Cc: alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org, Xi Wang Subject: [PATCH] ALSA: usb-audio: fix possible hang and overflow in parse_uac2_sample_rate_range() Date: Wed, 4 Jan 2012 12:39:09 -0500 Message-Id: <1325698749-5353-1-git-send-email-xi.wang@gmail.com> X-Mailer: git-send-email 1.7.5.4 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 avoid overflow. Signed-off-by: Xi Wang --- sound/usb/format.c | 5 ++++- 1 files changed, 4 insertions(+), 1 deletions(-) diff --git a/sound/usb/format.c b/sound/usb/format.c index 89421d1..a99de67 100644 --- a/sound/usb/format.c +++ b/sound/usb/format.c @@ -226,7 +226,7 @@ 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 +253,9 @@ static int parse_uac2_sample_rate_range(struct audioformat *fp, int nr_triplets, fp->rates |= snd_pcm_rate_to_rate_bit(rate); nr_rates++; + /* avoid overflow */ + if (nr_rates == KMALLOC_MAX_SIZE / sizeof(int)) + break; /* avoid endless loop */ if (res == 0) -- 1.7.5.4