Re: [PATCH 1/2] Fix format overflows

Krzysztof Opasiak
2017-02-21T06:13:45Z

Hi,

W dniu 2017-02-20 o 21:51, Jonathan Dieter pisze:
> 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@gmail.com>
> Signed-off-by: Jonathan Dieter <jdieter@lesbg.com>
> ---
> tools/usb/usbip/libsrc/usbip_common.c | 8 +++++++-
> tools/usb/usbip/libsrc/usbip_host_common.c | 25 ++++++++++++++++++++-----
> 2 files changed, 27 insertions(+), 6 deletions(-)
>
> diff --git a/tools/usb/usbip/libsrc/usbip_common.c b/tools/usb/usbip/libsrc/usbip_common.c
> index ac73710..fc875ee 100644
> --- a/tools/usb/usbip/libsrc/usbip_common.c
> +++ b/tools/usb/usbip/libsrc/usbip_common.c
> @@ -215,9 +215,15 @@ 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, SYSFS_BUS_ID_SIZE, "%s:%d.%d",

why not sizeof(busid)?

> + udev->busid, udev->bConfigurationValue, i);
> + if (size >= SYSFS_BUS_ID_SIZE) {

As above.

> + err("busid length %i >= SYSFS_BUS_ID_SIZE", size);
> + 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..690cd49 100644
> --- a/tools/usb/usbip/libsrc/usbip_host_common.c
> +++ b/tools/usb/usbip/libsrc/usbip_host_common.c
> @@ -40,13 +40,19 @@ 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, SYSFS_PATH_MAX, "%s/usbip_status",

The same here.

> + udev->path);
> + if (size >= SYSFS_PATH_MAX) {
> + err("usbip_status path length %i >= SYSFS_PATH_MAX", size);
> + return -1;
> + }
> +
>
> fd = open(status_attr_path, O_RDONLY);
> if (fd < 0) {
> @@ -218,6 +224,7 @@ 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 +244,18 @@ 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 >= SYSFS_PATH_MAX) {

hmmm this should be sizeof(sockfd_attr_path) not SYSFS_PATH_MAX

> + err("exported device path length %i >= SYSFS_PATH_MAX", size);
> + return -1;
> + }
>
> - snprintf(sockfd_buff, sizeof(sockfd_buff), "%d\n", sockfd);
> + size = snprintf(sockfd_buff, sizeof(sockfd_buff), "%d\n", sockfd);
> + if (size >= 30) {

Please don't hardcode such values in if. use sizeof() like one line above

> + err("socket length %i >= 30", size);
> + return -1;
> + }
>
> ret = write_sysfs_attribute(sockfd_attr_path, sockfd_buff,
> strlen(sockfd_buff));
>

Best regards,
--
Krzysztof Opasiak
Samsung R&D Institute Poland
Samsung Electronics