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SubjectRe: [PATCH] s390/ctcm: replace deprecated strncpy with strscpy
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On 23.10.23 21:35, 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 chid to be NUL-terminated based on its use with format
> strings:
>
> CTCM_DBF_TEXT_(SETUP, CTC_DBF_INFO, "%s(%s) %s", CTCM_FUNTAIL,
> chid, ok ? "OK" : "failed");
>
> Moreover, NUL-padding is not required as it is _only_ used in this one
> instance with a format string.
>
> 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.
>
> We can also drop the +1 from chid's declaration as we no longer need to
> be cautious about leaving a spot for a NUL-byte. Let's use the more
> idiomatic strscpy usage of (dest, src, sizeof(dest)) as this more
> closely ties the destination buffer to the length.
>
> 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>

LGTM, thank you!

Reviewed-by: Thorsten Winkler <twinkler@linux.ibm.com>
Tested-by: Thorsten Winkler <twinkler@linux.ibm.com>

> ---
> Note: build-tested only.
>
> Found with: $ rg "strncpy\("
> ---
> drivers/s390/net/ctcm_main.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/s390/net/ctcm_main.c b/drivers/s390/net/ctcm_main.c
> index 6faf27136024..ac15d7c2b200 100644
> --- a/drivers/s390/net/ctcm_main.c
> +++ b/drivers/s390/net/ctcm_main.c
> @@ -200,13 +200,13 @@ static void channel_free(struct channel *ch)
> static void channel_remove(struct channel *ch)
> {
> struct channel **c = &channels;
> - char chid[CTCM_ID_SIZE+1];
> + char chid[CTCM_ID_SIZE];
> int ok = 0;
>
> if (ch == NULL)
> return;
> else
> - strncpy(chid, ch->id, CTCM_ID_SIZE);
> + strscpy(chid, ch->id, sizeof(chid));
>
> channel_free(ch);
> while (*c) {
>
> ---
> base-commit: 9c5d00cb7b6bbc5a7965d9ab7d223b5402d1f02c
> change-id: 20231023-strncpy-drivers-s390-net-ctcm_main-c-f9180f470c69
>
> Best regards,
> --
> Justin Stitt <justinstitt@google.com>
>
>

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