On Wed, Oct 18, 2023 at 09:18:24PM +0000, Justin Stitt wrote: > strncpy() is deprecated for use on NUL-terminated destination strings > [1] and as such we should prefer more robust and less ambiguous string > interfaces. > > wl->chip.phy_fw_ver_str is obviously intended to be NUL-terminated by > the deliberate comment telling us as much. Furthermore, its only use is > drivers/net/wireless/ti/wlcore/debugfs.c shows us it should be > NUL-terminated since its used in scnprintf: > 492 | DRIVER_STATE_PRINT_STR(chip.phy_fw_ver_str); > which is defined as: > | #define DRIVER_STATE_PRINT_STR(x) DRIVER_STATE_PRINT(x, "%s") > ... > | #define DRIVER_STATE_PRINT(x, fmt) \ > | (res += scnprintf(buf + res, DRIVER_STATE_BUF_LEN - res,\ > | #x " = " fmt "\n", wl->x)) > > We can also see that NUL-padding is not required. > > Considering the above, a suitable replacement is `strscpy` [2] due to > the fact that it guarantees NUL-termination on the destination buffer > without unnecessarily NUL-padding. > > The very fact that a plain-english comment had to be made alongside a > manual NUL-byte assignment for such a simple purpose shows why strncpy > is faulty. It has non-obvious behavior that has to be clarified every > time it is used (and if it isn't then the reader suffers). > > Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1] > Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2] > Link: https://github.com/KSPP/linux/issues/90 > Cc: linux-hardening@xxxxxxxxxxxxxxx > Signed-off-by: Justin Stitt <justinstitt@xxxxxxxxxx> Yup, a clear case for strscpy. Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> -- Kees Cook
