| Message ID | 20231018-strncpy-drivers-net-wireless-ti-wl18xx-main-c-v2-1-ab828a491ce5@google.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | fb329e8b1d88dd09b6f46d7ba3d9243599221b68 |
| Delegated to: | Kalle Valo |
| Headers | show |
| Series | [v2] wifi: wl18xx: replace deprecated strncpy with strscpy | expand |
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@vger.kernel.org > Signed-off-by: Justin Stitt <justinstitt@google.com> Yup, a clear case for strscpy. Reviewed-by: Kees Cook <keescook@chromium.org>
Justin Stitt <justinstitt@google.com> 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@vger.kernel.org > Signed-off-by: Justin Stitt <justinstitt@google.com> > Reviewed-by: Kees Cook <keescook@chromium.org> Patch applied to wireless-next.git, thanks. fb329e8b1d88 wifi: wl18xx: replace deprecated strncpy with strscpy
diff --git a/drivers/net/wireless/ti/wl18xx/main.c b/drivers/net/wireless/ti/wl18xx/main.c index 0b3cf8477c6c..1e4a430d1543 100644 --- a/drivers/net/wireless/ti/wl18xx/main.c +++ b/drivers/net/wireless/ti/wl18xx/main.c @@ -1516,12 +1516,9 @@ static int wl18xx_handle_static_data(struct wl1271 *wl, struct wl18xx_static_data_priv *static_data_priv = (struct wl18xx_static_data_priv *) static_data->priv; - strncpy(wl->chip.phy_fw_ver_str, static_data_priv->phy_version, + strscpy(wl->chip.phy_fw_ver_str, static_data_priv->phy_version, sizeof(wl->chip.phy_fw_ver_str)); - /* make sure the string is NULL-terminated */ - wl->chip.phy_fw_ver_str[sizeof(wl->chip.phy_fw_ver_str) - 1] = '\0'; - wl1271_info("PHY firmware version: %s", static_data_priv->phy_version); return 0;
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> --- Changes in v2: - add wifi: to subject (thanks Jeff) - Link to v1: https://lore.kernel.org/r/20231017-strncpy-drivers-net-wireless-ti-wl18xx-main-c-v1-1-ed5322ec8068@google.com --- Note: build-tested only. Found with: $ rg "strncpy\(" --- drivers/net/wireless/ti/wl18xx/main.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) --- base-commit: 58720809f52779dc0f08e53e54b014209d13eebb change-id: 20231017-strncpy-drivers-net-wireless-ti-wl18xx-main-c-356a0272bab4 Best regards, -- Justin Stitt <justinstitt@google.com>