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-sc16is...
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@intel.com/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@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/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.
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
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