On Wed, 6 Dec 2023 14:29:39 +0800 kernel test robot <lkp@xxxxxxxxx> wrote: > Hi Hugo, > > kernel test robot noticed the following build warnings: > > [auto build test WARNING on d804987153e7bedf503f8e4ba649afe52cfd7f6d] > > url: https://github.com/intel-lab-lkp/linux/commits/Hugo-Villeneuve/serial-sc16is7xx-fix-snprintf-format-specifier-in-sc16is7xx_regmap_name/20231201-031413 > base: d804987153e7bedf503f8e4ba649afe52cfd7f6d > patch link: https://lore.kernel.org/r/20231130191050.3165862-2-hugo%40hugovil.com > patch subject: [PATCH 1/7] serial: sc16is7xx: fix snprintf format specifier in sc16is7xx_regmap_name() > config: x86_64-buildonly-randconfig-001-20231201 (https://download.01.org/0day-ci/archive/20231206/202312061443.Cknef7Uq-lkp@xxxxxxxxx/config) > compiler: gcc-12 (Debian 12.2.0-14) 12.2.0 > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231206/202312061443.Cknef7Uq-lkp@xxxxxxxxx/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@xxxxxxxxx> > | Closes: https://lore.kernel.org/oe-kbuild-all/202312061443.Cknef7Uq-lkp@xxxxxxxxx/ > > All warnings (new ones prefixed by >>): > > drivers/tty/serial/sc16is7xx.c: In function 'sc16is7xx_i2c_probe': > >> drivers/tty/serial/sc16is7xx.c:1703:41: warning: '%u' directive output may be truncated writing between 1 and 10 bytes into a region of size 2 [-Wformat-truncation=] > 1703 | snprintf(buf, sizeof(buf), "port%u", port_id); > | ^~ > In function 'sc16is7xx_regmap_name', > inlined from 'sc16is7xx_i2c_probe' at drivers/tty/serial/sc16is7xx.c:1805:17: > drivers/tty/serial/sc16is7xx.c:1703:36: note: directive argument in the range [0, 4294967294] > 1703 | snprintf(buf, sizeof(buf), "port%u", port_id); > | ^~~~~~~~ > drivers/tty/serial/sc16is7xx.c:1703:9: note: 'snprintf' output between 6 and 15 bytes into a destination of size 6 > 1703 | snprintf(buf, sizeof(buf), "port%u", port_id); > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Hi, the only solution I could find is to add this line just before snprintf: BUG_ON(port_id > MAX310X_MAX_PORTS); it allows us to have the smallest buffer size possible. One other solution would be to change port_id from "unsigned int" to "u8", and increase the buffer by an additional 2 bytes to silence the warning, but then wasting 2 bytes for each channel, like so: static const char *max310x_regmap_name(u8 port_id) { static char buf[ sizeof(MAX310X_PORT_NAME_SUFFIX __stringify(UCHAR_MAX))]; I prefer solution 1, unless there is another solution that I am unaware of. Hugo. > vim +1703 drivers/tty/serial/sc16is7xx.c > > 1698 > 1699 static const char *sc16is7xx_regmap_name(unsigned int port_id) > 1700 { > 1701 static char buf[6]; > 1702 > > 1703 snprintf(buf, sizeof(buf), "port%u", port_id); > 1704 > 1705 return buf; > 1706 } > 1707 > > -- > 0-DAY CI Kernel Test Service > https://github.com/intel/lkp-tests/wiki > -- Hugo Villeneuve
