s390/qeth: 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 new_entry->dbf_name to be NUL-terminated based on its use with
strcmp():
|       if (strcmp(entry->dbf_name, name) == 0) {

Moreover, NUL-padding is not required as new_entry is kzalloc'd just
before this assignment:
|       new_entry = kzalloc(sizeof(struct qeth_dbf_entry), GFP_KERNEL);

... rendering any future NUL-byte assignments (like the ones strncpy()
does) redundant.

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.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html
Link: https://github.com/KSPP/linux/issues/90
Signed-off-by: Justin Stitt <justinstitt@google.com>
Reviewed-by: Thorsten Winkler <twinkler@linux.ibm.com>
Tested-by: Thorsten Winkler <twinkler@linux.ibm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20231023-strncpy-drivers-s390-net-qeth_core_main-c-v1-1-e7ce65454446@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c
index cd78329..6af2511 100644 (file)
--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -6226,7 +6226,7 @@ static int qeth_add_dbf_entry(struct qeth_card *card, char *name)
        new_entry = kzalloc(sizeof(struct qeth_dbf_entry), GFP_KERNEL);
        if (!new_entry)
                goto err_dbg;
-       strncpy(new_entry->dbf_name, name, DBF_NAME_LEN);
+       strscpy(new_entry->dbf_name, name, sizeof(new_entry->dbf_name));
        new_entry->dbf_info = card->debug;
        mutex_lock(&qeth_dbf_list_mutex);
        list_add(&new_entry->dbf_list, &qeth_dbf_list);