Re: [PATCH] EDAC/mc_sysfs: refactor deprecated strncpy

[Justin Stitt]

On Tue, Sep 12, 2023 at 6:26 PM Justin Stitt <justinstitt@xxxxxxxxxx> wrote:
>
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
>
> We should prefer more robust and less ambiguous string interfaces.
>
> A suitable replacement is `strscpy_pad` [2] due to the fact that it guarantees
> NUL-termination on the destination buffer whilst maintaining the
> NUL-padding behavior that `strncpy` provides. This may not be strictly
> necessary but as I couldn't understand what this code does I wanted to
> ensure that the functionality is the same.
>
> 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@xxxxxxxxxxxxxxx
> Signed-off-by: Justin Stitt <justinstitt@xxxxxxxxxx>
> ---
> Note: build-tested only.
> ---
>  drivers/edac/edac_mc_sysfs.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/edac/edac_mc_sysfs.c b/drivers/edac/edac_mc_sysfs.c
> index 15f63452a9be..b303309a63cf 100644
> --- a/drivers/edac/edac_mc_sysfs.c
> +++ b/drivers/edac/edac_mc_sysfs.c
> @@ -229,8 +229,7 @@ static ssize_t channel_dimm_label_store(struct device *dev,
>         if (copy_count == 0 || copy_count >= sizeof(rank->dimm->label))
>                 return -EINVAL;
>
> -       strncpy(rank->dimm->label, data, copy_count);
> -       rank->dimm->label[copy_count] = '\0';
> +       strscpy_pad(rank->dimm->label, data, copy_count);
>
>         return count;
>  }
>
> ---
> base-commit: 2dde18cd1d8fac735875f2e4987f11817cc0bc2c
> change-id: 20230913-strncpy-drivers-edac-edac_mc_sysfs-c-e619b00124a3
>
> Best regards,
> --
> Justin Stitt <justinstitt@xxxxxxxxxx>
>

I typo'd my grep and initially missed refactoring another instance of
strncpy in this same file. v2 [1] resolves this.

[1]: https://lore.kernel.org/r/20230913-strncpy-drivers-edac-edac_mc_sysfs-c-v2-1-2d2e6bd43642@xxxxxxxxxx