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b=H4sIAI7WMmUC/x2N0QrCMAwAf2Xk2UBXJwx/RUTaLNOAdCWp0zL27 ys+Hfdyt4GxChtcuw2UVzFZUpP+1AG9QnoyytQcvPPn3nmHVjRRrjiprKyGefmyon1yftcGnQP xI4ZSWCsSRkfjEN0lkB+hRbPyLL//8Hbf9wN9+HSXgAAAAA== X-Developer-Key: i=justinstitt@google.com; a=ed25519; pk=tC3hNkJQTpNX/gLKxTNQKDmiQl6QjBNCGKJINqAdJsE= X-Developer-Signature: v=1; a=ed25519-sha256; t=1697830543; l=2313; i=justinstitt@google.com; s=20230717; h=from:subject:message-id; bh=zmP6Agkd7BUv41JUTgaRBkw1r6Q9BZkiPWT2tLR0LAQ=; b=qUt1cyoTbXs6qmJVgPAXz5mbtcGQzIOLTkM7z8UR/GVWZ8gVAAzFiOhg9+1gcHscXS/bles5K Hd71E9a1vbbDBn24xeS1hMCC89N3IDNnw1W+pJJ4CZNXEiLH5v1sOMH X-Mailer: b4 0.12.3 Message-ID: <20231020-strncpy-drivers-power-supply-surface_battery-c-v1-1-cabaea50e667@google.com> Subject: [PATCH] platform/surface: aggregator: replace deprecated strncpy with strscpy From: Justin Stitt To: Maximilian Luz , Sebastian Reichel Cc: linux-pm@vger.kernel.org, platform-driver-x86@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, Justin Stitt X-Spam-Status: No, score=-8.4 required=5.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on agentk.vger.email 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 (agentk.vger.email [0.0.0.0]); Fri, 20 Oct 2023 12:36:00 -0700 (PDT) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1780304443847499180 X-GMAIL-MSGID: 1780304443847499180 strncpy() is deprecated for use on NUL-terminated destination strings [1] and as such we should prefer more robust and less ambiguous string interfaces. We expect bat->name to be NUL-terminated based on its usage with strcmp(): power_supply_core.c: 445: return strcmp(psy->desc->name, name) == 0; ... and also by the manual `... - 1` for the length argument of the original strncpy() invocation. Furthermore, no NUL-padding is needed as bat is zero-allocated before calling spwr_battery_init(): 826: bat = devm_kzalloc(&sdev->dev, sizeof(*bat), GFP_KERNEL); 827: if (!bat) 828: return -ENOMEM; 829: 830: spwr_battery_init(bat, sdev, p->registry, p->name); ... this means any further NUL-byte assignments (like the ones that strncpy() does) are redundant. 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. Let's also opt to use the more idiomatic strscpy() usage of: (dest, src, sizeof(dest)). 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. Found with: $ rg "strncpy\(" --- drivers/power/supply/surface_battery.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- base-commit: bb55d7f7f7445abcc8db50e6a65d4315e79f75c7 change-id: 20231020-strncpy-drivers-power-supply-surface_battery-c-b0c84b05ac28 Best regards, -- Justin Stitt diff --git a/drivers/power/supply/surface_battery.c b/drivers/power/supply/surface_battery.c index 19d2f8834e56..196d290dc596 100644 --- a/drivers/power/supply/surface_battery.c +++ b/drivers/power/supply/surface_battery.c @@ -722,7 +722,7 @@ static void spwr_battery_init(struct spwr_battery_device *bat, struct ssam_devic struct ssam_event_registry registry, const char *name) { mutex_init(&bat->lock); - strncpy(bat->name, name, ARRAY_SIZE(bat->name) - 1); + strscpy(bat->name, name, sizeof(bat->name)); bat->sdev = sdev;