Re: [usb:usb-testing 7/12] drivers/usb/dwc3/core.c:1482:69: warning: '%d' directive output may be truncated writing between 1 and 11 bytes into a region of size 4

Johan Hovold
2024-04-24T06:41:58Z

On Wed, Apr 24, 2024 at 01:03:07PM +0800, kernel test robot wrote:
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing
> head: a160e1202ca318a85c70cf5831f172cc79a24c57
> commit: 846b4bacf2d48212f271fc1ef7488bcdf2c75bcb [7/12] usb: dwc3: core: Refactor PHY logic to support Multiport Controller
> config: s390-allyesconfig (https://download.01.org/0day-ci/archive/20240424/202404241215.Mib19Cu7-lkp@intel.com/config)
> compiler: s390-linux-gcc (GCC) 13.2.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240424/202404241215.Mib19Cu7-lkp@intel.com/reproduce)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202404241215.Mib19Cu7-lkp@intel.com/
>
> All warnings (new ones prefixed by >>):
>
> drivers/usb/dwc3/core.c: In function 'dwc3_core_get_phy':
> >> drivers/usb/dwc3/core.c:1482:69: warning: '%d' directive output may be truncated writing between 1 and 11 bytes into a region of size 4 [-Wformat-truncation=]
> 1482 | snprintf(phy_name, sizeof(phy_name), "usb2-%d", i);
> | ^~
> drivers/usb/dwc3/core.c:1482:63: note: directive argument in the range [-2147483641, 254]
> 1482 | snprintf(phy_name, sizeof(phy_name), "usb2-%d", i);

This version or s390-build of gcc appears to be confused as the
variable i is clearly in the range [0,254] in these for loops.

I also don't see this W=1 warning with my gcc-10 (aarch64).

It may be possible to work around this by using u8 type for the iterator
(and %u in the format), but I'm not sure we should be working around
compiler bugs like that.

> | ^~~~~~~~~
> drivers/usb/dwc3/core.c:1482:25: note: 'snprintf' output between 7 and 17 bytes into a destination of size 9
> 1482 | snprintf(phy_name, sizeof(phy_name), "usb2-%d", i);
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

> 1446 static int dwc3_core_get_phy(struct dwc3 *dwc)
> 1447 {

> 1450 char phy_name[9];
> 1451 int ret;
> 1452 int i;

> 1478 for (i = 0; i < dwc->num_usb2_ports; i++) {
> 1479 if (dwc->num_usb2_ports == 1)
> 1480 snprintf(phy_name, sizeof(phy_name), "usb2-phy");
> 1481 else
> > 1482 snprintf(phy_name, sizeof(phy_name), "usb2-%d", i);

> 1493 }

Johan