Re: [PATCH] net: macb: Truncate TX1519CNT for trailing NUL

[Kees Cook <kees@kernel.org>]

On Tue, Mar 11, 2025 at 03:12:00PM +0100, Andrew Lunn wrote:
> On Mon, Mar 10, 2025 at 03:24:16PM -0700, Kees Cook wrote:
> > GCC 15's -Wunterminated-string-initialization saw that this string was
> > being truncated. Adjust the initializer so that the needed final NUL
> > character will be present.
> 
> This is where we get into the ugliness of the ethtool API for strings.
> It is not actually NUL terminated. The code uses memcpy(), see:
> 
> https://elixir.bootlin.com/linux/v6.13.6/source/drivers/net/ethernet/cadence/macb_main.c#L3193
> 
> The kAPI is that userspace provides a big buffer, and the kernel then
> copies these strings into the buffer at 32 byte offsets. There is no
> requirement for a NUL between them since they are all 32 bytes long.

Oh right! Yes, I always forget these are not NUL terminated. Okay, I
will resend this with a proper __nonstring annotation. I see the title
use in drivers/net/ethernet/cadence/macb_main.c and can confirm it's not
using C String APIs.

-- 
Kees Cook