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