Re: [PATCH] s390/cio: replace deprecated strncpy with strscpy

Vasily Gorbik
2023-10-25T10:25:18Z

On Mon, Oct 23, 2023 at 07:24:38PM +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 both `params` and `id` to be NUL-terminated based on their
> usage with format strings:
>
> format_node_data(iuparams, iunodeid, &lir->incident_node);
> format_node_data(auparams, aunodeid, &lir->attached_node);
>
> switch (lir->iq.class) {
> case LIR_IQ_CLASS_DEGRADED:
> pr_warn("Link degraded: RS=%02x RSID=%04x IC=%02x "
> "IUPARAMS=%s IUNODEID=%s AUPARAMS=%s AUNODEID=%s\n",
> sei_area->rs, sei_area->rsid, lir->ic, iuparams,
> iunodeid, auparams, aunodeid);
>
> NUL-padding is not required as both `params` and `id` have been memset
> to 0:
>
> memset(params, 0, PARAMS_LEN);
> memset(id, 0, NODEID_LEN);
>
> 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.
>
> Note that there's no overread bugs in the current implementation as the
> string literal "n/a" has a size much smaller than PARAMS_LEN or
> NODEID_LEN. Nonetheless, let's favor strscpy().
>
> 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>
> ---
> Note: build-tested only.
>
> Found with: $ rg "strncpy\("
> ---
> drivers/s390/cio/chsc.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)

Applied, thank you!