linux-hardening - Re: [PATCH] randstruct: temporarily disable clang support

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Date:   Mon, 6 Feb 2023 15:41:05 -0800
From:   Fangrui Song <maskray@...gle.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Eric Biggers <ebiggers@...nel.org>,
        linux-hardening@...r.kernel.org, llvm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] randstruct: temporarily disable clang support

On Sat, Feb 4, 2023 at 11:06 AM Kees Cook <keescook@...omium.org> wrote:
>
> On Fri, Feb 03, 2023 at 11:42:01AM -0800, Eric Biggers wrote:
> > From: Eric Biggers <ebiggers@...gle.com>
> >
> > Randstruct with clang is currently unsafe to use in any clang release
> > that supports it, due to a clang bug that is causing miscompilations:
> > "-frandomize-layout-seed inconsistently randomizes all-function-pointers
> > structs" (https://github.com/llvm/llvm-project/issues/60349).  Disable
> > it temporarily until the bug is fixed and the fix is released in a clang
> > version that can be checked for.
> >
> > Fixes: 035f7f87b729 ("randstruct: Enable Clang support")
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Eric Biggers <ebiggers@...gle.com>
> > ---
> >  security/Kconfig.hardening | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening
> > index 53baa95cb644..aad16187148c 100644
> > --- a/security/Kconfig.hardening
> > +++ b/security/Kconfig.hardening
> > @@ -280,7 +280,8 @@ config ZERO_CALL_USED_REGS
> >  endmenu
> >
> >  config CC_HAS_RANDSTRUCT
> > -     def_bool $(cc-option,-frandomize-layout-seed-file=/dev/null)
> > +     # Temporarily disabled due to https://github.com/llvm/llvm-project/issues/60349
> > +     def_bool n
> >
> >  choice
> >       prompt "Randomize layout of sensitive kernel structures"
> >
> > base-commit: 7b753a909f426f2789d9db6f357c3d59180a9354
> > --
> > 2.39.1
>
> This should be fixed with greater precision -- i.e. this is nearly fixed
> in Clang now, and is likely to be backported. So I think we'll need
> versioned checks here.
>
> --
> Kees Cook
>

Bill has requested cherry-pick the llvm-project fix into the
release/16.x branch [1].
https://github.com/llvm/llvm-project-release-prs/pull/276
It may take one day to land.

[1]: https://github.com/llvm/llvm-project/tree/release/16.x

-- 
宋方睿