From: Hugo Villeneuve > Sent: 07 December 2023 17:53 ... > > 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. Or "port%c", '0' + port_id); Or maybe: size_t buflen = sizeof (buf); OPTIMIZER_HIDE_VAR(buflen); snprintf(buf, buflen, fmt, args); See https://godbolt.org/z/Wjz3xG5c4 Maybe there should be snprintf_may_truncate() (etc) in one of the headers. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
