Re: [PATCH v2] usbip: tools: fix GCC8 warning for strncpy

[shuah <shuah@kernel.org>]

On 7/25/19 7:22 AM, Liu, Changcheng wrote:
> GCC8 started emitting warning about using strncpy with number of bytes
> exactly equal destination size which could lead to non-zero terminated
> string being copied. Use "SYSFS_PATH_MAX - 1" & "SYSFS_BUS_ID_SIZE - 1"
> as number of bytes to ensure name is always zero-terminated.
> 
> Signed-off-by: Changcheng Liu <changcheng.liu@aliyun.com>
> ---
> v1 -> v2:
>   * Correct array tail index
> ---
>   tools/usb/usbip/libsrc/usbip_common.c        | 6 ++++--
>   tools/usb/usbip/libsrc/usbip_device_driver.c | 6 ++++--
>   2 files changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/usb/usbip/libsrc/usbip_common.c b/tools/usb/usbip/libsrc/usbip_common.c
> index bb424638d75b..b8d7d480595a 100644
> --- a/tools/usb/usbip/libsrc/usbip_common.c
> +++ b/tools/usb/usbip/libsrc/usbip_common.c
> @@ -226,8 +226,10 @@ int read_usb_device(struct udev_device *sdev, struct usbip_usb_device *udev)
>   	path = udev_device_get_syspath(sdev);
>   	name = udev_device_get_sysname(sdev);
>   
> -	strncpy(udev->path,  path,  SYSFS_PATH_MAX);
> -	strncpy(udev->busid, name, SYSFS_BUS_ID_SIZE);
> +	strncpy(udev->path,  path,  SYSFS_PATH_MAX - 1);
> +	udev->path[SYSFS_PATH_MAX - 1] = '\0';
> +	strncpy(udev->busid, name, SYSFS_BUS_ID_SIZE - 1);
> +	udev->busid[SYSFS_BUS_ID_SIZE - 1] = '\0';

strlcpy() would be better choice here. Any reason to not use that?

>   
>   	sscanf(name, "%u-%u", &busnum, &devnum);
>   	udev->busnum = busnum;
> diff --git a/tools/usb/usbip/libsrc/usbip_device_driver.c b/tools/usb/usbip/libsrc/usbip_device_driver.c
> index 5a3726eb44ab..051d7d3f443b 100644
> --- a/tools/usb/usbip/libsrc/usbip_device_driver.c
> +++ b/tools/usb/usbip/libsrc/usbip_device_driver.c
> @@ -91,7 +91,8 @@ int read_usb_vudc_device(struct udev_device *sdev, struct usbip_usb_device *dev)
>   	copy_descr_attr16(dev, &descr, idProduct);
>   	copy_descr_attr16(dev, &descr, bcdDevice);
>   
> -	strncpy(dev->path, path, SYSFS_PATH_MAX);
> +	strncpy(dev->path, path, SYSFS_PATH_MAX - 1);
> +	dev->path[SYSFS_PATH_MAX - 1] = '\0';
>   
>   	dev->speed = USB_SPEED_UNKNOWN;
>   	speed = udev_device_get_sysattr_value(sdev, "current_speed");
> @@ -110,7 +111,8 @@ int read_usb_vudc_device(struct udev_device *sdev, struct usbip_usb_device *dev)
>   	dev->busnum = 0;
>   
>   	name = udev_device_get_sysname(plat);
> -	strncpy(dev->busid, name, SYSFS_BUS_ID_SIZE);
> +	strncpy(dev->busid, name, SYSFS_BUS_ID_SIZE - 1);
> +	dev->busid[SYSFS_BUS_ID_SIZE - 1] = '\0';

strlcpy() would be better choice here. Any reason to not use that?

>   	return 0;
>   err:
>   	fclose(fd);
> 

thanks,
-- Shuah