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Date: Thu, 27 Jun 2019 08:15:34 +0200
From: Michal Hocko <mhocko@...nel.org>
To: Kees Cook <keescook@...omium.org>
Cc: Qian Cai <cai@....pw>, Catalin Marinas <catalin.marinas@....com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Alexander Potapenko <glider@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Christoph Lameter <cl@...ux.com>,
Masahiro Yamada <yamada.masahiro@...ionext.com>,
James Morris <jmorris@...ei.org>,
"Serge E. Hallyn" <serge@...lyn.com>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Kostya Serebryany <kcc@...gle.com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Sandeep Patil <sspatil@...roid.com>,
Laura Abbott <labbott@...hat.com>,
Randy Dunlap <rdunlap@...radead.org>, Jann Horn <jannh@...gle.com>,
Mark Rutland <mark.rutland@....com>, Marco Elver <elver@...gle.com>,
linux-mm@...ck.org, linux-security-module@...r.kernel.org,
kernel-hardening@...ts.openwall.com,
clang-built-linux@...glegroups.com
Subject: Re: [PATCH v8 1/2] mm: security: introduce init_on_alloc=1 and
init_on_free=1 boot options
On Wed 26-06-19 13:23:34, Kees Cook wrote:
> On Wed, Jun 26, 2019 at 02:15:49PM -0400, Qian Cai wrote:
> > On Wed, 2019-06-26 at 14:19 +0200, Alexander Potapenko wrote:
> > > Both init_on_alloc and init_on_free default to zero, but those defaults
> > > can be overridden with CONFIG_INIT_ON_ALLOC_DEFAULT_ON and
> > > CONFIG_INIT_ON_FREE_DEFAULT_ON.
> > > [...]
> > > +static int __init early_init_on_alloc(char *buf)
> > > +{
> > > + int ret;
> > > + bool bool_result;
> > > +
> > > + if (!buf)
> > > + return -EINVAL;
> > > + ret = kstrtobool(buf, &bool_result);
> > > + if (bool_result)
> > > + static_branch_enable(&init_on_alloc);
> > > + else
> > > + static_branch_disable(&init_on_alloc);
> > > + return ret;
> > > +}
> > > +early_param("init_on_alloc", early_init_on_alloc);
> >
> > Do those really necessary need to be static keys?
> >
> > Adding either init_on_free=0 or init_on_alloc=0 to the kernel cmdline will
> > generate a warning with kernels built with clang.
> >
> > [ 0.000000] static_key_disable(): static key 'init_on_free+0x0/0x4' used
> > before call to jump_label_init()
> > [ 0.000000] WARNING: CPU: 0 PID: 0 at ./include/linux/jump_label.h:317
> > early_init_on_free+0x1c0/0x200
> > [ 0.000000] Modules linked in:
> > [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 5.2.0-rc6-next-20190626+
> > #9
> > [ 0.000000] pstate: 60000089 (nZCv daIf -PAN -UAO)
>
> I think the issue here is that arm64 doesn't initialize static keys
> early enough.
This sounds familiar: http://lkml.kernel.org/r/CABXOdTd-cqHM_feAO1tvwn4Z=kM6WHKYAbDJ7LGfMvRPRPG7GA@mail.gmail.com
--
Michal Hocko
SUSE Labs
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