At Tue, 14 Feb 2012 05:18:48 -0500, Xi Wang wrote:

A malicious USB device could feed in a large nr_rates value. This would cause the subsequent call to kmemdup() to allocate a smaller buffer than expected, leading to out-of-bounds access.

This patch validates the nr_rates value and reuses the limit introduced in commit 4fa0e81b ("ALSA: usb-audio: fix possible hang and overflow in parse_uac2_sample_rate_range()").

Signed-off-by: Xi Wang xi.wang@gmail.com

Thanks, applied now.

Takashi

---

sound/usb/card.h | 1 + sound/usb/format.c | 4 +--- sound/usb/quirks.c | 6 +++++- 3 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/sound/usb/card.h b/sound/usb/card.h index a39edcc..da5fa1a 100644 --- a/sound/usb/card.h +++ b/sound/usb/card.h @@ -1,6 +1,7 @@ #ifndef __USBAUDIO_CARD_H #define __USBAUDIO_CARD_H

+#define MAX_NR_RATES 1024 #define MAX_PACKS 20 #define MAX_PACKS_HS (MAX_PACKS * 8) /* in high speed mode */ #define MAX_URBS 8 diff --git a/sound/usb/format.c b/sound/usb/format.c index e09aba1..ddfef57 100644 --- a/sound/usb/format.c +++ b/sound/usb/format.c @@ -209,8 +209,6 @@ 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

@@ -255,7 +253,7 @@ 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) {
  

• 	if (nr_rates >= MAX_NR_RATES) {
  	snd_printk(KERN_ERR "invalid uac2 rates\n");
  	break;
  }
  

diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c index a3ddac0..2781726 100644 --- a/sound/usb/quirks.c +++ b/sound/usb/quirks.c @@ -132,10 +132,14 @@ static int create_fixed_stream_quirk(struct snd_usb_audio *chip, unsigned *rate_table = NULL;

fp = kmemdup(quirk->data, sizeof(*fp), GFP_KERNEL);

• if (! fp) {

• if (!fp) { snd_printk(KERN_ERR "cannot memdup\n"); return -ENOMEM; }
• if (fp->nr_rates > MAX_NR_RATES) {

• kfree(fp);
  

• return -EINVAL;
  

• } if (fp->nr_rates > 0) { rate_table = kmemdup(fp->rate_table, sizeof(int) * fp->nr_rates, GFP_KERNEL);

-- 1.7.5.4