ALSA: usb-audio: avoid integer overflow in create_fixed_stream_quirk()

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>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/usb/card.h b/sound/usb/card.h
index a39edcc..da5fa1a 100644 (file)
--- 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 (file)
--- 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 (file)
--- 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);