linux-kernel - Re: [PATCH v2] net: macb: Add __nonstring annotations for unterminated strings

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Message-ID: <202503121005.DC5E16ACF8@keescook>
Date: Wed, 12 Mar 2025 10:07:11 -0700
From: Kees Cook <kees@...nel.org>
To: Bill Wendling <morbo@...gle.com>
Cc: Nicolas Ferre <nicolas.ferre@...rochip.com>,
	Claudiu Beznea <claudiu.beznea@...on.dev>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2] net: macb: Add __nonstring annotations for
 unterminated strings

On Tue, Mar 11, 2025 at 04:04:24PM -0700, Bill Wendling wrote:
> On Tue, Mar 11, 2025 at 3:44 PM Kees Cook <kees@...nel.org> wrote:
> >
> > When a character array without a terminating NUL character has a static
> > initializer, GCC 15's -Wunterminated-string-initialization will only
> > warn if the array lacks the "nonstring" attribute[1]. Mark the arrays
> > with __nonstring to and correctly identify the char array as "not a C
> 
> s/__nonstring to and correctly/__nonstring to correctly/ ?

Whoops. Rewriting glitch. Yes, "and" should be dropped. I will fix this
locally for all the patches with the same language and send v3 for this
one.

> 
> > string" and thereby eliminate the warning.
> >
> > Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117178 [1]
> > Signed-off-by: Kees Cook <kees@...nel.org>
> > ---
> >  v1: https://lore.kernel.org/lkml/20250310222415.work.815-kees@kernel.org/
> >  v2: switch to __nonstring annotation
> > Cc: Nicolas Ferre <nicolas.ferre@...rochip.com>
> > Cc: Claudiu Beznea <claudiu.beznea@...on.dev>
> > Cc: Andrew Lunn <andrew+netdev@...n.ch>
> > Cc: "David S. Miller" <davem@...emloft.net>
> > Cc: Eric Dumazet <edumazet@...gle.com>
> > Cc: Jakub Kicinski <kuba@...nel.org>
> > Cc: Paolo Abeni <pabeni@...hat.com>
> > Cc: netdev@...r.kernel.org
> > ---
> >  drivers/net/ethernet/cadence/macb.h | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
> > index 2847278d9cd4..003483073223 100644
> > --- a/drivers/net/ethernet/cadence/macb.h
> > +++ b/drivers/net/ethernet/cadence/macb.h
> > @@ -1027,7 +1027,7 @@ struct gem_stats {
> >   * this register should contribute to.
> >   */
> >  struct gem_statistic {
> > -       char stat_string[ETH_GSTRING_LEN];
> > +       char stat_string[ETH_GSTRING_LEN] __nonstring;
> >         int offset;
> >         u32 stat_bits;
> >  };
> > @@ -1068,6 +1068,7 @@ static const struct gem_statistic gem_statistics[] = {
> >         GEM_STAT_TITLE(TX512CNT, "tx_512_1023_byte_frames"),
> >         GEM_STAT_TITLE(TX1024CNT, "tx_1024_1518_byte_frames"),
> >         GEM_STAT_TITLE(TX1519CNT, "tx_greater_than_1518_byte_frames"),
> > +
> 
> Is this an errant inclusion? :-)

Ah, yeah, I had removed the truncation change but the whitespace change
stuck around. Also fixing!

> 
> Reviewed-by: Bill Wendling <morbo@...gle.com>

Thanks!

-Kees

-- 
Kees Cook