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Message-ID: <202209071613.A08F0F9225@keescook>
Date: Wed, 7 Sep 2022 16:18:40 -0700
From: Kees Cook <keescook@...omium.org>
To: Nick Desaulniers <ndesaulniers@...gle.com>
Cc: Nathan Chancellor <nathan@...nel.org>, Tom Rix <trix@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Vlastimil Babka <vbabka@...e.cz>,
"Steven Rostedt (Google)" <rostedt@...dmis.org>,
David Gow <davidgow@...gle.com>,
Yury Norov <yury.norov@...il.com>,
Masami Hiramatsu <mhiramat@...nel.org>,
Sander Vanheule <sander@...nheule.net>,
linux-hardening@...r.kernel.org, llvm@...ts.linux.dev,
Peter Zijlstra <peterz@...radead.org>,
Josh Poimboeuf <jpoimboe@...nel.org>,
Dan Williams <dan.j.williams@...el.com>,
Isabella Basso <isabbasso@...eup.net>,
Eric Dumazet <edumazet@...gle.com>,
Rasmus Villemoes <linux@...musvillemoes.dk>,
Eric Biggers <ebiggers@...gle.com>,
Hannes Reinecke <hare@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] fortify: Fix __compiletime_strlen() under
UBSAN_BOUNDS_LOCAL
On Tue, Sep 06, 2022 at 07:36:46PM -0700, Nick Desaulniers wrote:
> On Fri, Sep 2, 2022 at 1:43 PM Kees Cook <keescook@...omium.org> wrote:
> >
> > Co-developed-by: Nick Desaulniers <ndesaulniers@...gle.com>
>
> That's overly generous of you!
Well, it was a lot of work to track down, and you wrote it up that way,
I just moved things around a little bit. :)
> Anyways, the disassembly LGTM and the bot also came back green.
>
> Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
> Tested-by: Android Treehugger Robot
> Link: https://android-review.googlesource.com/c/kernel/common/+/2206839
Thank you!
> Another thought, Nikita suggested that you could also compare mode 1 vs mode 3:
> https://github.com/llvm/llvm-project/issues/57510#issuecomment-1235126343
Yeah, it could work (I tried this as well), but I think the better
approach is checking index 0.
> That said, since mode 3 returns 0 for "unknown" I'd imagine that
> wouldn't be pretty since it wouldn't be a direct comparison against
> __p_size.
Yeah -- it is a little weird. I might come back to this if we get more
glitches like this in the future.
--
Kees Cook
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