Re: [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

We expect chid to be NUL-terminated based on its use with format

			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: [1]
Link: [2]
Cc: linux-hardening@xxxxxxxxxxxxxxx
Signed-off-by: Justin Stitt <justinstitt@xxxxxxxxxx>

LGTM, thank you!

Reviewed-by: Thorsten Winkler <twinkler@xxxxxxxxxxxxx>
Tested-by: Thorsten Winkler <twinkler@xxxxxxxxxxxxx>

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)
-		strncpy(chid, ch->id, CTCM_ID_SIZE);
+		strscpy(chid, ch->id, sizeof(chid));
  	while (*c) {

base-commit: 9c5d00cb7b6bbc5a7965d9ab7d223b5402d1f02c
change-id: 20231023-strncpy-drivers-s390-net-ctcm_main-c-f9180f470c69

Best regards,
Justin Stitt <justinstitt@xxxxxxxxxx>

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