Re: [PATCH v2] tracing: replace multiple deprecated strncpy with memcpy

[Kees Cook <kees@kernel.org>]

On Mon, Oct 14, 2024 at 02:13:14PM -0700, 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.
> 
> String copy operations involving manual pointer offset and length
> calculations followed by explicit NUL-byte assignments are best changed
> to either strscpy or memcpy.
> 
> strscpy is not a drop-in replacement as @len would need a one subtracted
> from it to avoid truncating the source string.
> 
> To not sabotage readability of the current code, use memcpy (retaining
> the manual NUL assignment) as this unambiguously describes the desired
> behavior.

We know the destination must have a NUL-terminated string. Is the src
NUL terminated? Looking at parse_pred(), it seems like no? And we can't
use memtostr_pad() here because the source buffer size isn't known at
compile time. Okay then. And there are no NUL bytes in the "str + s"
span, so yeah, it looks like memcpy() is best.

Reviewed-by: Kees Cook <kees@kernel.org>

-- 
Kees Cook