[PATCH] i2c: cp2615: replace deprecated strncpy with strscpy

[PATCH] i2c: cp2615: replace deprecated strncpy with strscpy

[Justin Stitt]

`strncpy` is deprecated for use on NUL-terminated destination strings [1].

We should prefer more robust and less ambiguous string interfaces.

We expect name to be NUL-terminated based on its numerous uses with
functions that expect NUL-terminated strings.

For example in i2c-core-base.c +1533:
| dev_dbg(&adap->dev, "adapter [%s] registered\n", adap->name);

NUL-padding is not required as `adap` is already zero-alloacted with:
| adap = devm_kzalloc(&usbif->dev, sizeof(struct i2c_adapter), GFP_KERNEL);

With the above in mind, a suitable replacement is `strscpy` [2] due to
the fact that it guarantees NUL-termination on the destination buffer
without unnecessarily NUL-padding.

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>
---
 drivers/i2c/busses/i2c-cp2615.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-cp2615.c b/drivers/i2c/busses/i2c-cp2615.c
index 3ded28632e4c..20f8f7c9a8cd 100644
--- a/drivers/i2c/busses/i2c-cp2615.c
+++ b/drivers/i2c/busses/i2c-cp2615.c
@@ -298,7 +298,7 @@ cp2615_i2c_probe(struct usb_interface *usbif, const struct usb_device_id *id)
 	if (!adap)
 		return -ENOMEM;
 
-	strncpy(adap->name, usbdev->serial, sizeof(adap->name) - 1);
+	strscpy(adap->name, usbdev->serial, sizeof(adap->name));
 	adap->owner = THIS_MODULE;
 	adap->dev.parent = &usbif->dev;
 	adap->dev.of_node = usbif->dev.of_node;

---
base-commit: 2cf0f715623872823a72e451243bbf555d10d032
change-id: 20230920-strncpy-drivers-i2c-busses-i2c-cp2615-c-aada0fe2aa71

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

Re: [PATCH] i2c: cp2615: replace deprecated strncpy with strscpy

[Kees Cook]

On Wed, Sep 20, 2023 at 08:08:52AM +0000, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
> 
> We should prefer more robust and less ambiguous string interfaces.
> 
> We expect name to be NUL-terminated based on its numerous uses with
> functions that expect NUL-terminated strings.
> 
> For example in i2c-core-base.c +1533:
> | dev_dbg(&adap->dev, "adapter [%s] registered\n", adap->name);
> 
> NUL-padding is not required as `adap` is already zero-alloacted with:
> | adap = devm_kzalloc(&usbif->dev, sizeof(struct i2c_adapter), GFP_KERNEL);
> 
> With the above in mind, a suitable replacement is `strscpy` [2] due to
> the fact that it guarantees NUL-termination on the destination buffer
> without unnecessarily NUL-padding.
> 
> 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>

Thanks for the clear commit log! Looks good to me.

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook

Re: [PATCH] i2c: cp2615: replace deprecated strncpy with strscpy

[Wolfram Sang]

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On Wed, Sep 20, 2023 at 08:08:52AM +0000, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
> 
> We should prefer more robust and less ambiguous string interfaces.
> 
> We expect name to be NUL-terminated based on its numerous uses with
> functions that expect NUL-terminated strings.
> 
> For example in i2c-core-base.c +1533:
> | dev_dbg(&adap->dev, "adapter [%s] registered\n", adap->name);
> 
> NUL-padding is not required as `adap` is already zero-alloacted with:
> | adap = devm_kzalloc(&usbif->dev, sizeof(struct i2c_adapter), GFP_KERNEL);
> 
> With the above in mind, a suitable replacement is `strscpy` [2] due to
> the fact that it guarantees NUL-termination on the destination buffer
> without unnecessarily NUL-padding.
> 
> 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>

Applied to for-next, thanks!


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