Re: [PATCH 14/22] [media] usbvision-i2c: fix format overflow warning

On 17/07/17 14:57, Arnd Bergmann wrote:

On Mon, Jul 17, 2017 at 2:53 PM, Hans Verkuil [off-list ref] wrote:

quoted

On 14/07/17 14:07, Arnd Bergmann wrote:

quoted

gcc-7 notices that we copy a fixed length string into another
string of the same size, with additional characters:

drivers/media/usb/usbvision/usbvision-i2c.c: In function 'usbvision_i2c_register':
drivers/media/usb/usbvision/usbvision-i2c.c:190:36: error: '%d' directive writing between 1 and 11 bytes into a region of size between 0 and 47 [-Werror=format-overflow=]
  sprintf(usbvision->i2c_adap.name, "%s-%d-%s", i2c_adap_template.name,
                                    ^~~~~~~~~~
drivers/media/usb/usbvision/usbvision-i2c.c:190:2: note: 'sprintf' output between 4 and 76 bytes into a destination of size 48

We know this is fine as the template name is always "usbvision", so
we can easily avoid the warning by using this as the format string
directly.

Hmm, how about replacing sprintf by snprintf? That feels a lot safer (this is very
old code, it's not surprising it is still using sprintf).

With snprintf(), you will still get a -Wformat-truncation warning. One
of my patches
disables that warning by default, but Mauro likes build-testing with
"make W=1", so
it would still show up then.

However, we can do both: replace the string and use snprintf().

Yes please!

Regards,

	Hans