On Wed, 6 Dec 2023 14:29:39 +0800 kernel test robot lkp@intel.com 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-sc16is... 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@i...) 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@i...)
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/202312061443.Cknef7Uq-lkp@intel.com/
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