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b=H4sIACQKDGUC/x3NQQrCQAxA0auUrA1M04LWq4iLdiZqEMeQ1DJSe vcOXb7N/ys4m7DDtVnBeBGXb65oTw3E15ifjJKqgQJ1YaAWfbYc9Y/JZGFzlKy/GT/iEceiFAo qvzFiF/tzuAzUT1OCWlPjh5TjdLtv2w6OsGzyeQAAAA== X-Developer-Key: i=justinstitt@google.com; a=ed25519; pk=tC3hNkJQTpNX/gLKxTNQKDmiQl6QjBNCGKJINqAdJsE= X-Developer-Signature: v=1; a=ed25519-sha256; t=1695287845; l=2368; i=justinstitt@google.com; s=20230717; h=from:subject:message-id; bh=atTHwoOS3ax7JJoTHqO0Ih64Objj21oOjS1ymiaTpOM=; b=CzS67ZEeOOLd2kKtKJHGJgC5Pd6bB/JpQ7ZFhdM3DO2Y3bTZopyE9hqqeykaMwcB9uPwxcM/Q PEwK3UJgOzGA86AZCv6t/FGU40dAcrqJp4OWV8hS0LdNF4kYJ6BqAQZ X-Mailer: b4 0.12.3 Message-ID: <20230921-strncpy-drivers-input-misc-axp20x-pek-c-v1-1-f7f6f4a5cf81@google.com> Subject: [PATCH] Input: axp20x-pek - refactor deprecated strncpy From: Justin Stitt To: Dmitry Torokhov , Chen-Yu Tsai Cc: linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, Justin Stitt X-Spam-Status: No, score=-8.1 required=5.0 tests=BAYES_00,DATE_IN_PAST_06_12, DKIMWL_WL_MED,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (howler.vger.email [0.0.0.0]); Thu, 21 Sep 2023 13:11:46 -0700 (PDT) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1777689687740866437 X-GMAIL-MSGID: 1777689687740866437 `strncpy` is deprecated for use on NUL-terminated destination strings [1] and as such we should prefer more robust and less ambiguous string interfaces. Ensuring we have a trailing NUL-byte and checking the length of bytes copied are both intrinsic behavior of strscpy. Therefore, a suitable replacement is `strscpy` [2] due to the fact that it guarantees NUL-termination on the destination buffer without unnecessarily NUL-padding. It should be noted that the original code can silently truncate and so can this refactoring. However, a check could be added if truncation is an issue: | len = strscpy(val_str, buf, sizeof(val_str)); | if (len < 0) { // add this | return -E2BIG; // or -EINVAL | } Also, now check for `len > 0` instead of just a truthy `len` because `len` is now a signed type and we could run into problems if strscpy returned -E2BIG which would pass the truthy test. 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 --- Note: build-tested only. --- drivers/input/misc/axp20x-pek.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) --- base-commit: 2cf0f715623872823a72e451243bbf555d10d032 change-id: 20230921-strncpy-drivers-input-misc-axp20x-pek-c-3c4708924bbd Best regards, -- Justin Stitt diff --git a/drivers/input/misc/axp20x-pek.c b/drivers/input/misc/axp20x-pek.c index 4581606a28d6..abcf78785b45 100644 --- a/drivers/input/misc/axp20x-pek.c +++ b/drivers/input/misc/axp20x-pek.c @@ -134,16 +134,14 @@ static ssize_t axp20x_store_attr(struct device *dev, { struct axp20x_pek *axp20x_pek = dev_get_drvdata(dev); char val_str[20]; - size_t len; + ssize_t len; int ret, i; unsigned int val, idx = 0; unsigned int best_err = UINT_MAX; - val_str[sizeof(val_str) - 1] = '\0'; - strncpy(val_str, buf, sizeof(val_str) - 1); - len = strlen(val_str); + len = strscpy(val_str, buf, sizeof(val_str)); - if (len && val_str[len - 1] == '\n') + if (len > 0 && val_str[len - 1] == '\n') val_str[len - 1] = '\0'; ret = kstrtouint(val_str, 10, &val);