Re: [PATCH v4 1/2] usbip: Fix-format-overflow

[Shuah Khan]

On 02/27/2017 01:31 AM, Jonathan Dieter wrote:
> The usbip userspace tools call sprintf()/snprintf() and don't check for
> the return value which can lead the paths to overflow, truncating the
> final file in the path.
> 
> More urgently, GCC 7 now warns that these aren't checked with
> -Wformat-overflow, and with -Werror enabled in configure.ac, that makes
> these tools unbuildable.
> 
> This patch fixes these problems by replacing sprintf() with snprintf() in
> one place and adding checks for the return value of snprintf().
> 
> Reviewed-by: Peter Senna Tschudin <peter.senna@xxxxxxxxx>
> Signed-off-by: Jonathan Dieter <jdieter@xxxxxxxxx>

Greg,

Please pick this up.

Acked-by: Shuah Khan <shuahkh@xxxxxxxxxxxxxxx>

thanks,
-- Shuah

> ---
> Changes since v3
>  * Cast sizeof to long unsigned when printing errors to fix building for 32-bit
>    architectures
> 
>  tools/usb/usbip/libsrc/usbip_common.c      |  9 ++++++++-
>  tools/usb/usbip/libsrc/usbip_host_common.c | 28 +++++++++++++++++++++++-----
>  2 files changed, 31 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/usb/usbip/libsrc/usbip_common.c b/tools/usb/usbip/libsrc/usbip_common.c
> index ac73710..1517a23 100644
> --- a/tools/usb/usbip/libsrc/usbip_common.c
> +++ b/tools/usb/usbip/libsrc/usbip_common.c
> @@ -215,9 +215,16 @@ int read_usb_interface(struct usbip_usb_device *udev, int i,
>  		       struct usbip_usb_interface *uinf)
>  {
>  	char busid[SYSFS_BUS_ID_SIZE];
> +	int size;
>  	struct udev_device *sif;
>  
> -	sprintf(busid, "%s:%d.%d", udev->busid, udev->bConfigurationValue, i);
> +	size = snprintf(busid, sizeof(busid), "%s:%d.%d",
> +			udev->busid, udev->bConfigurationValue, i);
> +	if (size < 0 || (unsigned int)size >= sizeof(busid)) {
> +		err("busid length %i >= %lu or < 0", size,
> +		    (long unsigned)sizeof(busid));
> +		return -1;
> +	}
>  
>  	sif = udev_device_new_from_subsystem_sysname(udev_context, "usb", busid);
>  	if (!sif) {
> diff --git a/tools/usb/usbip/libsrc/usbip_host_common.c b/tools/usb/usbip/libsrc/usbip_host_common.c
> index 9d41522..6ff7b60 100644
> --- a/tools/usb/usbip/libsrc/usbip_host_common.c
> +++ b/tools/usb/usbip/libsrc/usbip_host_common.c
> @@ -40,13 +40,20 @@ struct udev *udev_context;
>  static int32_t read_attr_usbip_status(struct usbip_usb_device *udev)
>  {
>  	char status_attr_path[SYSFS_PATH_MAX];
> +	int size;
>  	int fd;
>  	int length;
>  	char status;
>  	int value = 0;
>  
> -	snprintf(status_attr_path, SYSFS_PATH_MAX, "%s/usbip_status",
> -		 udev->path);
> +	size = snprintf(status_attr_path, sizeof(status_attr_path),
> +			"%s/usbip_status", udev->path);
> +	if (size < 0 || (unsigned int)size >= sizeof(status_attr_path)) {
> +		err("usbip_status path length %i >= %lu or < 0", size,
> +		    (long unsigned)sizeof(status_attr_path));
> +		return -1;
> +	}
> +
>  
>  	fd = open(status_attr_path, O_RDONLY);
>  	if (fd < 0) {
> @@ -218,6 +225,7 @@ int usbip_export_device(struct usbip_exported_device *edev, int sockfd)
>  {
>  	char attr_name[] = "usbip_sockfd";
>  	char sockfd_attr_path[SYSFS_PATH_MAX];
> +	int size;
>  	char sockfd_buff[30];
>  	int ret;
>  
> @@ -237,10 +245,20 @@ int usbip_export_device(struct usbip_exported_device *edev, int sockfd)
>  	}
>  
>  	/* only the first interface is true */
> -	snprintf(sockfd_attr_path, sizeof(sockfd_attr_path), "%s/%s",
> -		 edev->udev.path, attr_name);
> +	size = snprintf(sockfd_attr_path, sizeof(sockfd_attr_path), "%s/%s",
> +			edev->udev.path, attr_name);
> +	if (size < 0 || (unsigned int)size >= sizeof(sockfd_attr_path)) {
> +		err("exported device path length %i >= %lu or < 0", size,
> +		    (long unsigned)sizeof(sockfd_attr_path));
> +		return -1;
> +	}
>  
> -	snprintf(sockfd_buff, sizeof(sockfd_buff), "%d\n", sockfd);
> +	size = snprintf(sockfd_buff, sizeof(sockfd_buff), "%d\n", sockfd);
> +	if (size < 0 || (unsigned int)size >= sizeof(sockfd_buff)) {
> +		err("socket length %i >= %lu or < 0", size,
> +		    (long unsigned)sizeof(sockfd_buff));
> +		return -1;
> +	}
>  
>  	ret = write_sysfs_attribute(sockfd_attr_path, sockfd_buff,
>  				    strlen(sockfd_buff));
>