From: Nathan Chancellor <nathan@kernel.org>
To: Bill Wendling <morbo@google.com>
Cc: Kees Cook <kees@kernel.org>, Vincent Mailhol <mailhol@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Justin Stitt <justinstitt@google.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH 2/2] randstruct: report bad casts as warnings rather than notes
Date: Fri, 4 Sep 2026 13:24:15 -0700 [thread overview]
Message-ID: <20260904202415.GA2787252@ax162> (raw)
In-Reply-To: <CAGG=3QUHtqFVCEcnxXO9fan_RBT_jjWtBbA8ECpQeiC1dKMnvg@mail.gmail.com>
On Fri, Sep 04, 2026 at 11:14:19AM -0700, Bill Wendling wrote:
> Hi Kees,
>
> On Thu, Sep 3, 2026 at 4:24 PM Kees Cook <kees@kernel.org> wrote:
> >
> > find_bad_casts() reports a cast between two randomized structure pointer
> > types with inform(), which renders as a "note:". It has done so since
> > the plugin was originally added, while using error() freely for attribute
> > misuse, UAPI structs, and version mismatches.
> >
> > Clang's implementation of the same check has always been stricter:
> > it rejects such a cast as a full error. There is no reason for the GCC
> > side to be effectively silent about the same problem.
> >
> > Build tested ARCH=x86_64 with CONFIG_RANDSTRUCT_FULL=y and GCC 14.2.0:
> > allmodconfig clean, and defconfig clean under three different random
> > seeds. A deliberate bad cast is still reported, now as a warning, at the
> > correct line and column.
> >
> > Signed-off-by: Kees Cook <kees@kernel.org>
> > ---
> > scripts/gcc-plugins/randomize_layout_plugin.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/scripts/gcc-plugins/randomize_layout_plugin.c b/scripts/gcc-plugins/randomize_layout_plugin.c
> > index e2bd9ba08089..1e66f45fe29b 100644
> > --- a/scripts/gcc-plugins/randomize_layout_plugin.c
> > +++ b/scripts/gcc-plugins/randomize_layout_plugin.c
> > @@ -22,7 +22,7 @@
> > #define ORIG_TYPE_NAME(node) \
> > (TYPE_NAME(TYPE_MAIN_VARIANT(node)) != NULL_TREE ? ((const unsigned char *)IDENTIFIER_POINTER(TYPE_NAME(TYPE_MAIN_VARIANT(node)))) : (const unsigned char *)"anonymous")
> >
> > -#define INFORM(loc, msg, ...) inform(loc, "randstruct: " msg, ##__VA_ARGS__)
> > +#define INFORM(loc, msg, ...) warning_at(loc, 0, "randstruct: " msg, ##__VA_ARGS__)
>
> Why not make this an error instead of a warning?
Yeah, it seems odd to mention that Clang's implementation has always
treated this as an error then not match its behavior. If this cannot be
made an error, I think the commit message should call out why.
--
Cheers,
Nathan
next prev parent reply other threads:[~2026-09-04 20:24 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-03 23:24 [PATCH 0/2] randstruct: fix container_of() false positives after __mptr removal Kees Cook
2026-09-03 23:24 ` [PATCH 1/2] " Kees Cook
2026-09-03 23:24 ` [PATCH 2/2] randstruct: report bad casts as warnings rather than notes Kees Cook
2026-09-04 18:14 ` Bill Wendling
2026-09-04 20:24 ` Nathan Chancellor [this message]
2026-09-05 0:48 ` Kees Cook
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