linux-hardening - Re: [PATCH v2] scsi: lpfc: replace deprecated strncpy with strscpy

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Date: Mon, 26 Feb 2024 16:53:32 -0800
From: Kees Cook <keescook@...omium.org>
To: Justin Stitt <justinstitt@...gle.com>
Cc: James Smart <james.smart@...adcom.com>,
	Dick Kennedy <dick.kennedy@...adcom.com>,
	"James E.J. Bottomley" <jejb@...ux.ibm.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2] scsi: lpfc: replace deprecated strncpy with strscpy

On Mon, Feb 26, 2024 at 11:53:44PM +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 ae->value_string to be NUL-terminated because there's a
> comment that says as much; these attr strings are also used with other
> string APIs, further cementing the fact.
> 
> Now, the question of whether or not to NUL-pad the destination buffer:
> lpfc_fdmi_rprt_defer() initializes vports (all zero-initialized), then
> we call lpfc_fdmi_cmd() with each vport and a mask. Then, inside of
> lpfc_fdmi_cmd() we check each bit in the mask to invoke the proper
> callback. Importantly, the zero-initialized vport is passed in as the
> "attr" parameter. Seeing this:
> |	struct lpfc_fdmi_attr_string *ae = attr;
> ... we can tell that ae->value_string is entirely zero-initialized. Due
> to this, NUL-padding is _not_ required as it would be redundant.
> 
> Considering the above, a suitable replacement is `strscpy` [2].
> 
> 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@...r.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook