On Fri, Sep 22, 2017 at 3:19 PM, Takashi Iwai tiwai@suse.de 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@google.com
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@googlegroups.com. For more options, visit https://groups.google.com/d/optout.