On Fri, Sep 22, 2017 at 3:19 PM, Takashi Iwai <tiwai@xxxxxxx> wrote:
> On Fri, 22 Sep 2017 14:56:06 +0200,
> Andrey Konovalov wrote:
>>
>> Hi!
>>
>> I've got the following report while fuzzing the kernel with syzkaller.
>>
>> On commit ebb2c2437d8008d46796902ff390653822af6cc4 (Sep 18).
>>
>> It seems that there's no check that control_header has enough space
>> for uac1_ac_header_descriptor in snd_usb_create_streams().
>
> Indeed, this might be an issue.
> Does the patch below fix the problem?
I believe it does. It does fix the crash with my reproducer.
I'm not sure if the (rest_bytes <= 0) check is actually needed though.
It seems that if snd_usb_find_csint_desc() returns a non-null value,
it'll always be within the buffer.
Tested-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
>
>
> Takashi
>
> ---
> diff --git a/sound/usb/card.c b/sound/usb/card.c
> index 3dc36d913550..fc969efbb37c 100644
> --- a/sound/usb/card.c
> +++ b/sound/usb/card.c
> @@ -221,6 +221,7 @@ static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
> struct usb_interface_descriptor *altsd;
> void *control_header;
> int i, protocol;
> + int rest_bytes;
>
> /* find audiocontrol interface */
> host_iface = &usb_ifnum_to_if(dev, ctrlif)->altsetting[0];
> @@ -235,6 +236,13 @@ static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
> return -EINVAL;
> }
>
> + rest_bytes = (void *)(host_iface->extra + host_iface->extralen) -
> + control_header;
> + if (rest_bytes <= 0) {
> + dev_err(&dev->dev, "invalid control header\n");
> + return -EINVAL;
> + }
> +
> switch (protocol) {
> default:
> dev_warn(&dev->dev,
> @@ -245,11 +253,21 @@ static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
> case UAC_VERSION_1: {
> struct uac1_ac_header_descriptor *h1 = control_header;
>
> + if (rest_bytes < sizeof(*h1)) {
> + dev_err(&dev->dev, "too short v1 buffer descriptor\n");
> + return -EINVAL;
> + }
> +
> if (!h1->bInCollection) {
> dev_info(&dev->dev, "skipping empty audio interface (v1)\n");
> return -EINVAL;
> }
>
> + if (rest_bytes < h1->bLength) {
> + dev_err(&dev->dev, "invalid buffer length (v1)\n");
> + return -EINVAL;
> + }
> +
> if (h1->bLength < sizeof(*h1) + h1->bInCollection) {
> dev_err(&dev->dev, "invalid UAC_HEADER (v1)\n");
> return -EINVAL;
>
> --
> You received this message because you are subscribed to the Google Groups "syzkaller" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller+unsubscribe@xxxxxxxxxxxxxxxx.
> For more options, visit https://groups.google.com/d/optout.
_______________________________________________
Alsa-devel mailing list
Alsa-devel@xxxxxxxxxxxxxxxx
http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
