ACK: [PATCH] ALSA: usb-audio: Check out-of-bounds access by corrupted buffer descriptor

[Colin Ian King]

On 19/07/18 15:27, Paolo Pisati wrote:
> From: Takashi Iwai <tiwai at suse.de>
> 
> 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 at google.com>
> Tested-by: Andrey Konovalov <andreyknvl at google.com>
> Cc: <stable at vger.kernel.org>
> Signed-off-by: Takashi Iwai <tiwai at suse.de>
> (cherry picked from commit bfc81a8bc18e3c4ba0cbaa7666ff76be2f998991)
> Signed-off-by: Paolo Pisati <paolo.pisati at canonical.com>
> ---
>  sound/usb/card.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/sound/usb/card.c b/sound/usb/card.c
> index ab433a0..9189dbc 100644
> --- a/sound/usb/card.c
> +++ b/sound/usb/card.c
> @@ -218,6 +218,7 @@ 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];
> @@ -232,6 +233,15 @@ 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;
> +
> +	/* 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:
>  		snd_printdd(KERN_WARNING "unknown interface protocol %#02x, assuming v1\n",
> @@ -241,11 +251,21 @@ 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) {
>  			snd_printk(KERN_INFO "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) {
>  			snd_printk(KERN_ERR "invalid UAC_HEADER (v1)\n");
>  			return -EINVAL;
> 

Looks OK to me.

Acked-by: Colin Ian King <colin.king at canonical.com>