On Mon, Oct 23, 2023 at 07:39:39PM +0000, 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 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
> [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]>
struct qeth_dbf_entry {
char dbf_name[DBF_NAME_LEN];
The sizeof() replace looks right to me.
Reviewed-by: Kees Cook <[email protected]>
-Kees
> ---
> Note: build-tested only.
>
> Found with: $ rg "strncpy\("
> ---
> drivers/s390/net/qeth_core_main.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/s390/net/qeth_core_main.c
> b/drivers/s390/net/qeth_core_main.c
> index cd783290bde5..6af2511e070c 100644
> --- 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);
>
> ---
> base-commit: 9c5d00cb7b6bbc5a7965d9ab7d223b5402d1f02c
> change-id: 20231023-strncpy-drivers-s390-net-qeth_core_main-c-0b0ee08672ec
>
> Best regards,
> --
> Justin Stitt <[email protected]>
>
>
--
Kees Cook
