2023-09-27 10:12:02

by Justin Stitt

Subject: [PATCH] c2port: replace deprecated strncpy with strscpy

`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: [email protected]
Signed-off-by: Justin Stitt <[email protected]>
---
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 <[email protected]>

2023-09-28 06:27:34

by Arnd Bergmann

Subject: Re: [PATCH] c2port: replace deprecated strncpy with strscpy

On Wed, Sep 27, 2023, at 07:20, 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.
>
> 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: [email protected]
> Signed-off-by: Justin Stitt <[email protected]>

Reviewed-by: Arnd Bergmann <[email protected]>