From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xi Wang Subject: [PATCH v2] ALSA: usb-audio: fix possible hang and overflow in parse_uac2_sample_rate_range() Date: Sun, 08 Jan 2012 09:02:52 -0500 Message-ID: <4F09A20C.7090705@gmail.com> References: <1325698749-5353-1-git-send-email-xi.wang@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-iy0-f179.google.com (mail-iy0-f179.google.com [209.85.210.179]) by alsa0.perex.cz (Postfix) with ESMTP id 7FCFB1038FA for ; Sun, 8 Jan 2012 15:02:58 +0100 (CET) Received: by iaae16 with SMTP id e16so5329687iaa.38 for ; Sun, 08 Jan 2012 06:02:57 -0800 (PST) In-Reply-To: <1325698749-5353-1-git-send-email-xi.wang@gmail.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: alsa-devel-bounces@alsa-project.org Errors-To: alsa-devel-bounces@alsa-project.org To: Takashi Iwai , Jaroslav Kysela , Clemens Ladisch , Daniel Mack , Wolfgang Breyha Cc: alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org, Xi Wang List-Id: alsa-devel@alsa-project.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