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Date:   Wed, 27 Sep 2023 05:20:58 +0000
Mime-Version: 1.0
Message-ID: <20230927-strncpy-drivers-misc-c2port-core-c-v1-1-978f6d220a54@google.com>
Subject: [PATCH] c2port: replace deprecated strncpy with strscpy
From:   Justin Stitt <justinstitt@google.com>
To:     Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org,
        Justin Stitt <justinstitt@google.com>
Content-Type: text/plain; charset="utf-8"
Precedence: bulk

`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 `c2dev->name` to be NUL-terminated based on its usage with
format strings:
|       dev_info(c2dev->dev, "C2 port %s removed\n", c2dev->name);

Moreover, NUL-padding is _not_ required as c2dev is zero-allocated:
|       c2dev = kzalloc(sizeof(struct c2port_device), GFP_KERNEL);

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 drop `C2PORT_NAME_LEN - 1` for `sizeof(dest)` which is more
idiomatic strscpy usage.

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>
---
Note: build-tested only.
---
 drivers/misc/c2port/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/misc/c2port/core.c b/drivers/misc/c2port/core.c
index f574c83b82cf..2bb1dd2511f9 100644
--- a/drivers/misc/c2port/core.c
+++ b/drivers/misc/c2port/core.c
@@ -923,7 +923,7 @@ struct c2port_device *c2port_device_register(char *name,
 	}
 	dev_set_drvdata(c2dev->dev, c2dev);
 
-	strncpy(c2dev->name, name, C2PORT_NAME_LEN - 1);
+	strscpy(c2dev->name, name, sizeof(c2dev->name));
 	c2dev->ops = ops;
 	mutex_init(&c2dev->mutex);
 

---
base-commit: 6465e260f48790807eef06b583b38ca9789b6072
change-id: 20230927-strncpy-drivers-misc-c2port-core-c-aa196361fec5

Best regards,
--
Justin Stitt <justinstitt@google.com>