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Date: Wed, 8 Mar 2017 21:49:56 +0000
From: Russell King - ARM Linux <linux@...linux.org.uk>
To: Thomas Garnier <thgarnie@...gle.com>
Cc: Arnd Bergmann <arnd@...db.de>, David Howells <dhowells@...hat.com>,
Al Viro <viro@...iv.linux.org.uk>,
Dave Hansen <dave.hansen@...el.com>,
René Nyffenegger <mail@...enyffenegger.ch>,
Andrew Morton <akpm@...ux-foundation.org>,
Kees Cook <keescook@...omium.org>,
"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
Petr Mladek <pmladek@...e.com>, Andy Lutomirski <luto@...nel.org>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Nicolas Pitre <nicolas.pitre@...aro.org>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
Helge Deller <deller@....de>, Rik van Riel <riel@...hat.com>,
Ingo Molnar <mingo@...nel.org>,
John Stultz <john.stultz@...aro.org>,
Thomas Gleixner <tglx@...utronix.de>,
Oleg Nesterov <oleg@...hat.com>,
Stanislav Kinsburskiy <skinsbursky@...tuozzo.com>,
Pavel Tikhomirov <ptikhomirov@...tuozzo.com>,
Stephen Smalley <sds@...ho.nsa.gov>,
Frederic Weisbecker <fweisbec@...il.com>,
Ingo Molnar <mingo@...hat.com>, "H . Peter Anvin" <hpa@...or.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Dmitry Safonov <dsafonov@...tuozzo.com>,
Borislav Petkov <bp@...en8.de>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Brian Gerst <brgerst@...il.com>,
Alexander Potapenko <glider@...gle.com>,
Jan Beulich <JBeulich@...e.com>, Will Deacon <will.deacon@....com>,
Catalin Marinas <catalin.marinas@....com>,
Mark Rutland <mark.rutland@....com>,
James Morse <james.morse@....com>,
Chris Metcalf <cmetcalf@...lanox.com>,
Laura Abbott <labbott@...hat.com>,
Andre Przywara <andre.przywara@....com>, linux-api@...r.kernel.org,
linux-kernel@...r.kernel.org, x86@...nel.org,
linux-arm-kernel@...ts.infradead.org,
kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH v1 3/4] arm/syscalls: Specific usage of
verify_pre_usermode_state
On Wed, Mar 08, 2017 at 01:38:43PM -0800, Thomas Garnier wrote:
> Implement specific usage of verify_pre_usermode_state for user-mode
> returns for arm.
> ---
> Based on next-20170308
> ---
> arch/arm/Kconfig | 1 +
> arch/arm/kernel/entry-common.S | 5 +++++
> 2 files changed, 6 insertions(+)
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 0d4e71b42c77..704fd8f197fa 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -12,6 +12,7 @@ config ARM
> select ARCH_HAVE_CUSTOM_GPIO_H
> select ARCH_HAS_GCOV_PROFILE_ALL
> select ARCH_MIGHT_HAVE_PC_PARPORT
> + select ARCH_NO_SYSCALL_VERIFY_PRE_USERMODE_STATE
> select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
> select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT if CPU_V7
> select ARCH_SUPPORTS_ATOMIC_RMW
> diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
> index eb5cd77bf1d8..80cfdc7fabde 100644
> --- a/arch/arm/kernel/entry-common.S
> +++ b/arch/arm/kernel/entry-common.S
> @@ -39,6 +39,9 @@
> ret_fast_syscall:
> UNWIND(.fnstart )
> UNWIND(.cantunwind )
> + push {r0} @ save returned r0
> + bl verify_pre_usermode_state
> + pop {r0} @ restore r0
This really makes the fast exit utterly pointless, and we might as well
rip all that out.
--
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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