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

[Vineeth Vijayan]

On 10/23/23 21:24, 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@xxxxxxxxxxxxxxx
> Signed-off-by: Justin Stitt<justinstitt@xxxxxxxxxx>

LGTM. Thank you.

Reviewed-by: Vineeth Vijayan <vneethv@xxxxxxxxxxxxx>

I can push this to s390-tree and Heiko/Vasily will upstream it.

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