3.2.47-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Xi Wang <xi.wang@xxxxxxxxx>
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 <tiwai@xxxxxxx>
Signed-off-by: Xi Wang <xi.wang@xxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
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)
--
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