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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@vger.kernel.org Signed-off-by: Justin Stitt <justinstitt@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: Kalle Valo <kvalo@kernel.org> Link: https://lore.kernel.org/r/20231018-strncpy-drivers-net-wireless-ti-wl18xx-main-c-v2-1-ab828a491ce5@google.com
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.