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| author | Xi Wang <xi.wang@gmail.com> | 2012-01-08 09:02:52 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-06-07 12:46:48 -0700 |
| commit | 44f059fb742aac78cffdab5e0d8fe0c9910c1ded (patch) | |
| tree | b3b6fc1cf6d587aff9061d90c2a0b95cc9d16f88 | |
| parent | 3b1a317977a8d16d743e8f85ed9a5a7f668b61d5 (diff) | |
| download | lwn-44f059fb742aac78cffdab5e0d8fe0c9910c1ded.tar.gz lwn-44f059fb742aac78cffdab5e0d8fe0c9910c1ded.zip | |
ALSA: usb-audio: fix possible hang and overflow in parse_uac2_sample_rate_range()
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@suse.de>
Signed-off-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Cc: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | 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 8d042dce0d16..be212a0a5f73 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) |