ACK/Cmnt: [PATCH] USB: fix out-of-bounds in usb_set_configuration

[Stefan Bader]

On 20.07.2018 15:20, Paolo Pisati wrote:
> From: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
> 
> Andrey Konovalov reported a possible out-of-bounds problem for a USB interface
> association descriptor.  He writes:
> 	It seems there's no proper size check of a USB_DT_INTERFACE_ASSOCIATION
> 	descriptor. It's only checked that the size is >= 2 in
> 	usb_parse_configuration(), so find_iad() might do out-of-bounds access
> 	to intf_assoc->bInterfaceCount.
> 
> And he's right, we don't check for crazy descriptors of this type very well, so
> resolve this problem.  Yet another issue found by syzkaller...
> 
> Reported-by: Andrey Konovalov <andreyknvl at google.com>
> Tested-by: Andrey Konovalov <andreyknvl at google.com>
> Cc: stable <stable at vger.kernel.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
> (cherry picked from commit bd7a3fe770ebd8391d1c7d072ff88e9e76d063eb)
> Signed-off-by: Paolo Pisati <paolo.pisati at canonical.com>
Acked-by: Stefan Bader <stefan.bader at canonical.com>
> ---
Needs CVE-2017-16531 added.

>  drivers/usb/core/config.c    | 14 +++++++++++---
>  include/uapi/linux/usb/ch9.h |  1 +
>  2 files changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
> index 9b05e88..755d82f 100644
> --- a/drivers/usb/core/config.c
> +++ b/drivers/usb/core/config.c
> @@ -513,15 +513,23 @@ static int usb_parse_configuration(struct usb_device *dev, int cfgidx,
>  
>  		} else if (header->bDescriptorType ==
>  				USB_DT_INTERFACE_ASSOCIATION) {
> +			struct usb_interface_assoc_descriptor *d;
> +
> +			d = (struct usb_interface_assoc_descriptor *)header;
> +			if (d->bLength < USB_DT_INTERFACE_ASSOCIATION_SIZE) {
> +				dev_warn(ddev,
> +					 "config %d has an invalid interface association descriptor of length %d, skipping\n",
> +					 cfgno, d->bLength);
> +				continue;
> +			}
> +
>  			if (iad_num == USB_MAXIADS) {
>  				dev_warn(ddev, "found more Interface "
>  					       "Association Descriptors "
>  					       "than allocated for in "
>  					       "configuration %d\n", cfgno);
>  			} else {
> -				config->intf_assoc[iad_num] =
> -					(struct usb_interface_assoc_descriptor
> -					*)header;
> +				config->intf_assoc[iad_num] = d;
>  				iad_num++;
>  			}
>  
> diff --git a/include/uapi/linux/usb/ch9.h b/include/uapi/linux/usb/ch9.h
> index aa33fd1..400196c 100644
> --- a/include/uapi/linux/usb/ch9.h
> +++ b/include/uapi/linux/usb/ch9.h
> @@ -705,6 +705,7 @@ struct usb_interface_assoc_descriptor {
>  	__u8  iFunction;
>  } __attribute__ ((packed));
>  
> +#define USB_DT_INTERFACE_ASSOCIATION_SIZE	8
>  
>  /*-------------------------------------------------------------------------*/
>  
> 


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