From: Ard Biesheuvel <ardb@kernel.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Herbert Xu <herbert@gondor.apana.org.au>,
kernel test robot <lkp@intel.com>,
Peter Oberparleiter <oberpar@linux.ibm.com>,
Kees Cook <keescook@chromium.org>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
kbuild-all@lists.01.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux Crypto Mailing List <linux-crypto@vger.kernel.org>
Subject: Re: lib/crypto/chacha.c:65:1: warning: the frame size of 1604 bytes is larger than 1024 bytes
Date: Thu, 27 Aug 2020 12:41:53 +0200 [thread overview]
Message-ID: <CAMj1kXGpX+g_t4aAz5yGs-c+PG+NLnu1j9_QLJ6teWTjJ1FkMQ@mail.gmail.com> (raw)
In-Reply-To: <CAK8P3a1nOL+BbvGAM3-aiH-mfzmFYgfFL2dWJKd8=Rw-WosP=w@mail.gmail.com>
On Thu, 27 Aug 2020 at 11:20, Arnd Bergmann <arnd@arndb.de> wrote:
>
> On Thu, Aug 27, 2020 at 10:42 AM Ard Biesheuvel <ardb@kernel.org> wrote:
> >
> > In that case, I suppose we should simply disable instrumentation for
> > chacha_permute()? It is a straight-forward arithmetic transformation
> > on a u32[16] array, where ubsan has limited value afaict.
>
> I guess that always works as a last resort, but shouldn't we first try
> to figure out why ubsan even makes a difference and whether the
> object code without ubsan looks like a reasonable representation
> of the source form?
>
> Since it really is a fairly simple transformation, I would have
> expected the compiler to not emit any ubsan checks. If gcc
> only gets confused about the fixed offsets possibly overflowing
> the fixed-length array, maybe it helps to give it a little extra
> information like (untested):
>
> --- a/lib/crypto/chacha.c
> +++ b/lib/crypto/chacha.c
> @@ -13,7 +13,7 @@
> #include <asm/unaligned.h>
> #include <crypto/chacha.h>
>
> -static void chacha_permute(u32 *x, int nrounds)
> +static void chacha_permute(u32 x[16], int nrounds)
> {
> int i;
>
That does not help, unfortunately.
What does seem to work is
struct chacha_state { u32 x[16]; };
struct chacha_state chacha_permute(struct chacha_state st, int nrounds)
{
struct chacha_state ret = st;
u32 *x = ret.x;
...
return st;
}
(and updating the caller accordingly, obviously)
next prev parent reply other threads:[~2020-08-27 10:42 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-27 3:52 lib/crypto/chacha.c:65:1: warning: the frame size of 1604 bytes is larger than 1024 bytes kernel test robot
2020-08-27 8:05 ` Herbert Xu
2020-08-27 8:10 ` Ard Biesheuvel
2020-08-27 8:24 ` Herbert Xu
2020-08-27 17:34 ` Linus Torvalds
2020-08-27 17:55 ` Linus Torvalds
2020-08-27 18:42 ` Kees Cook
2020-08-27 19:02 ` Linus Torvalds
2020-08-27 19:32 ` Kees Cook
2020-08-27 19:11 ` Arnd Bergmann
2020-08-27 19:34 ` Kees Cook
2020-08-27 20:08 ` Linus Torvalds
2020-08-27 8:33 ` Arnd Bergmann
2020-08-27 8:42 ` Ard Biesheuvel
2020-08-27 9:19 ` Arnd Bergmann
2020-08-27 10:41 ` Ard Biesheuvel [this message]
2020-08-27 11:51 ` Herbert Xu
2020-08-27 16:25 ` Arnd Bergmann
2020-09-19 17:27 kernel test robot
2020-10-18 19:13 kernel test robot
2020-10-19 15:47 ` Joe Perches
2020-10-20 8:00 ` David Laight
2020-10-20 10:13 ` Joe Perches
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAMj1kXGpX+g_t4aAz5yGs-c+PG+NLnu1j9_QLJ6teWTjJ1FkMQ@mail.gmail.com \
--to=ardb@kernel.org \
--cc=arnd@arndb.de \
--cc=aryabinin@virtuozzo.com \
--cc=herbert@gondor.apana.org.au \
--cc=kbuild-all@lists.01.org \
--cc=keescook@chromium.org \
--cc=linux-crypto@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=lkp@intel.com \
--cc=oberpar@linux.ibm.com \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).