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From: Alexander Potapenko <glider@google.com>
To: Kees Cook <keescook@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Elena Reshetova <elena.reshetova@intel.com>,
	 "the arch/x86 maintainers" <x86@kernel.org>,
	Andy Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	 Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	 Mark Rutland <mark.rutland@arm.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	 Jann Horn <jannh@google.com>,
	"Perla, Enrico" <enrico.perla@intel.com>,
	 Kernel Hardening <kernel-hardening@lists.openwall.com>,
	linux-arm-kernel@lists.infradead.org,
	 Linux Memory Management List <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 2/5] init_on_alloc: Unpessimize default-on builds
Date: Thu, 26 Mar 2020 16:48:41 +0100
Message-ID: <CAG_fn=X0DVwqLaHJTO6Jw7TGcMSm77GKHinrd0m_6y0SzWOrFA@mail.gmail.com> (raw)
In-Reply-To: <20200324203231.64324-3-keescook@chromium.org>

On Tue, Mar 24, 2020 at 9:32 PM Kees Cook <keescook@chromium.org> wrote:
>
> Right now, the state of CONFIG_INIT_ON_ALLOC_DEFAULT_ON (and
> ...ON_FREE...) did not change the assembly ordering of the static branch
> tests. Use the new jump_label macro to check CONFIG settings to default
> to the "expected" state, unpessimizes the resulting assembly code.
>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  include/linux/mm.h | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 059658604dd6..64e911159ffa 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2665,7 +2665,8 @@ static inline void kernel_poison_pages(struct page *page, int numpages,
>  DECLARE_STATIC_KEY_MAYBE(CONFIG_INIT_ON_ALLOC_DEFAULT_ON, init_on_alloc);
>  static inline bool want_init_on_alloc(gfp_t flags)
>  {
> -       if (static_branch_unlikely(&init_on_alloc) &&
> +       if (static_branch_maybe(CONFIG_INIT_ON_ALLOC_DEFAULT_ON,
> +                               &init_on_alloc) &&
>             !page_poisoning_enabled())
>                 return true;
>         return flags & __GFP_ZERO;
> @@ -2674,7 +2675,8 @@ static inline bool want_init_on_alloc(gfp_t flags)
>  DECLARE_STATIC_KEY_MAYBE(CONFIG_INIT_ON_FREE_DEFAULT_ON, init_on_free);
>  static inline bool want_init_on_free(void)
>  {
> -       return static_branch_unlikely(&init_on_free) &&
> +       return static_branch_maybe(CONFIG_INIT_ON_FREE_DEFAULT_ON,
> +                                  &init_on_free) &&
>                !page_poisoning_enabled();
>  }
>
> --
> 2.20.1
>
Reviewed-by: Alexander Potapenko <glider@google.com>

-- 
Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-Straße, 33
80636 München

Geschäftsführer: Paul Manicle, Halimah DeLaine Prado
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg

  reply index

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-24 20:32 [PATCH v2 0/5] Optionally randomize kernel stack offset each syscall Kees Cook
2020-03-24 20:32 ` [PATCH v2 1/5] jump_label: Provide CONFIG-driven build state defaults Kees Cook
2020-03-24 22:06   ` Peter Zijlstra
2020-03-24 20:32 ` [PATCH v2 2/5] init_on_alloc: Unpessimize default-on builds Kees Cook
2020-03-26 15:48   ` Alexander Potapenko [this message]
2020-03-24 20:32 ` [PATCH v2 3/5] stack: Optionally randomize kernel stack offset each syscall Kees Cook
2020-03-30 11:25   ` Mark Rutland
2020-03-30 18:18     ` Kees Cook
2020-03-30 18:27     ` Kees Cook
2020-03-24 20:32 ` [PATCH v2 4/5] x86/entry: Enable random_kstack_offset support Kees Cook
2020-03-28 22:26   ` Kees Cook
2020-03-24 20:32 ` [PATCH v2 5/5] arm64: entry: " Kees Cook
2020-03-25 13:21   ` Mark Rutland
2020-03-25 20:22     ` Kees Cook
2020-03-26 11:15       ` Mark Rutland
2020-03-26 16:31         ` Kees Cook
2020-03-30 11:26           ` Mark Rutland
2020-03-24 21:28 ` [PATCH v2 0/5] Optionally randomize kernel stack offset each syscall Jann Horn
2020-03-24 23:07   ` Kees Cook
2020-03-25 12:15     ` Reshetova, Elena
2020-03-25 20:27       ` Kees Cook
2020-03-25 23:20         ` Jann Horn
2020-03-26 17:18           ` Kees Cook

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