CVE-2017-16529: Out-of-bounds Read (CWE-125)
value: The snd_usb_create_streams function in sound/usb/card.c in the Linux kernel before 4.13.6 allows local users to cause a denial of service (out-of-bounds read and system crash) or possibly have unspecified other impact via a crafted USB device.
CWE description: The product reads data past the end, or before the beginning, of the intended buffer.
CVSS v3 base score: 6.6
Published: 2017-11-04T01:29Z
Repository: https://github.com/torvalds/linux
Language: C
Files changed: sound/usb/card.c
Commit date: 2017-09-22 16:21:31 +0200
Commit message: ALSA: usb-audio: Check out-of-bounds access by corrupted buffer descriptor

When a USB-audio device receives a maliciously adjusted or corrupted
buffer descriptor, the USB-audio driver may access an out-of-bounce
value at its parser.  This was detected by syzkaller, something like:

  BUG: KASAN: slab-out-of-bounds in usb_audio_probe+0x27b2/0x2ab0
  Read of size 1 at addr ffff88006b83a9e8 by task kworker/0:1/24
  CPU: 0 PID: 24 Comm: kworker/0:1 Not tainted 4.14.0-rc1-42251-gebb2c2437d80 #224
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
  Workqueue: usb_hub_wq hub_event
  Call Trace:
   __dump_stack lib/dump_stack.c:16
   dump_stack+0x292/0x395 lib/dump_stack.c:52
   print_address_description+0x78/0x280 mm/kasan/report.c:252
   kasan_report_error mm/kasan/report.c:351
   kasan_report+0x22f/0x340 mm/kasan/report.c:409
   __asan_report_load1_noabort+0x19/0x20 mm/kasan/report.c:427
   snd_usb_create_streams sound/usb/card.c:248
   usb_audio_probe+0x27b2/0x2ab0 sound/usb/card.c:605
   usb_probe_interface+0x35d/0x8e0 drivers/usb/core/driver.c:361
   really_probe drivers/base/dd.c:413
   driver_probe_device+0x610/0xa00 drivers/base/dd.c:557
   __device_attach_driver+0x230/0x290 drivers/base/dd.c:653
   bus_for_each_drv+0x161/0x210 drivers/base/bus.c:463
   __device_attach+0x26e/0x3d0 drivers/base/dd.c:710
   device_initial_probe+0x1f/0x30 drivers/base/dd.c:757
   bus_probe_device+0x1eb/0x290 drivers/base/bus.c:523
   device_add+0xd0b/0x1660 drivers/base/core.c:1835
   usb_set_configuration+0x104e/0x1870 drivers/usb/core/message.c:1932
   generic_probe+0x73/0xe0 drivers/usb/core/generic.c:174
   usb_probe_device+0xaf/0xe0 drivers/usb/core/driver.c:266
   really_probe drivers/base/dd.c:413
   driver_probe_device+0x610/0xa00 drivers/base/dd.c:557
   __device_attach_driver+0x230/0x290 drivers/base/dd.c:653
   bus_for_each_drv+0x161/0x210 drivers/base/bus.c:463
   __device_attach+0x26e/0x3d0 drivers/base/dd.c:710
   device_initial_probe+0x1f/0x30 drivers/base/dd.c:757
   bus_probe_device+0x1eb/0x290 drivers/base/bus.c:523
   device_add+0xd0b/0x1660 drivers/base/core.c:1835
   usb_new_device+0x7b8/0x1020 drivers/usb/core/hub.c:2457
   hub_port_connect drivers/usb/core/hub.c:4903
   hub_port_connect_change drivers/usb/core/hub.c:5009
   port_event drivers/usb/core/hub.c:5115
   hub_event+0x194d/0x3740 drivers/usb/core/hub.c:5195
   process_one_work+0xc7f/0x1db0 kernel/workqueue.c:2119
   worker_thread+0x221/0x1850 kernel/workqueue.c:2253
   kthread+0x3a1/0x470 kernel/kthread.c:231
   ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431

This patch adds the checks of out-of-bounce accesses at appropriate
places and bails out when it goes out of the given buffer.

Reported-by: Andrey Konovalov <andreyknvl@google.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Diff: diff --git a/sound/usb/card.c b/sound/usb/card.c
index 3dc36d91355020..23d1d23aefec37 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -219,10 +219,11 @@ static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
 	struct usb_device *dev = chip->dev;
 	struct usb_host_interface *host_iface;
 	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];
 	control_header = snd_usb_find_csint_desc(host_iface->extra,
 						 host_iface->extralen,
@@ -233,25 +234,44 @@ static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
 	if (!control_header) {
 		dev_err(&dev->dev, "cannot find UAC_HEADER\n");
 		return -EINVAL;
 	}
 
+	rest_bytes = (void *)(host_iface->extra + host_iface->extralen) -
+		control_header;
+
+	/* just to be sure -- this shouldn't hit at all */
+	if (rest_bytes <= 0) {
+		dev_err(&dev->dev, "invalid control header\n");
+		return -EINVAL;
+	}
+
 	switch (protocol) {
 	default:
 		dev_warn(&dev->dev,
 			 "unknown interface protocol %#02x, assuming v1\n",
 			 protocol);
 		/* fall through */
 
 	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;
 		}
 

Fixed code: 	int rest_bytes;
	rest_bytes = (void *)(host_iface->extra + host_iface->extralen) -
		control_header;

	/* just to be sure -- this shouldn't hit at all */
	if (rest_bytes <= 0) {
		dev_err(&dev->dev, "invalid control header\n");
		return -EINVAL;
	}

		if (rest_bytes < sizeof(*h1)) {
			dev_err(&dev->dev, "too short v1 buffer descriptor\n");
			return -EINVAL;
		}

		if (rest_bytes < h1->bLength) {
			dev_err(&dev->dev, "invalid buffer length (v1)\n");
			return -EINVAL;
		}