From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f200.google.com (mail-qt0-f200.google.com [209.85.216.200]) by kanga.kvack.org (Postfix) with ESMTP id 391AB6B0005 for ; Tue, 26 Jun 2018 08:53:38 -0400 (EDT) Received: by mail-qt0-f200.google.com with SMTP id 5-v6so3651659qta.1 for ; Tue, 26 Jun 2018 05:53:38 -0700 (PDT) Received: from mx1.redhat.com (mx3-rdu2.redhat.com. [66.187.233.73]) by mx.google.com with ESMTPS id r23-v6si1449134qtj.405.2018.06.26.05.53.37 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 26 Jun 2018 05:53:37 -0700 (PDT) Subject: Re: [v2 PATCH] add param that allows bootline control of hardened usercopy From: Christoph von Recklinghausen References: <1530017430-5394-1-git-send-email-crecklin@redhat.com> Message-ID: <06bde22f-3e28-e6f3-dab0-9bc8bd5973b8@redhat.com> Date: Tue, 26 Jun 2018 08:53:36 -0400 MIME-Version: 1.0 In-Reply-To: <1530017430-5394-1-git-send-email-crecklin@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: owner-linux-mm@kvack.org List-ID: To: keescook@chromium.org, labbott@redhat.com, pabeni@redhat.com, "linux-mm@kvack.org >> Linux-MM" , linux-kernel@vger.kernel.org On 06/26/2018 08:50 AM, Chris von Recklinghausen wrote: > Enabling HARDENED_USER_COPY causes measurable regressions in the > networking performances, up to 8% under UDP flood. > > A generic distro may want to enable HARDENED_USER_COPY in their default > kernel config, but at the same time, such distro may want to be able to > avoid the performance penalties in with the default configuration and > disable the stricter check on a per-boot basis. > > This change adds a boot parameter that to conditionally disable > HARDENED_USERCOPY at boot time. > > v1->v2: > remove CONFIG_HUC_DEFAULT_OFF > default is now enabled, boot param disables > move check to __check_object_size so as to not break optimization of > __builtin_constant_p() > include linux/atomic.h before linux/jump_label.h > > Signed-off-by: Chris von Recklinghausen > --- > .../admin-guide/kernel-parameters.rst | 1 + > .../admin-guide/kernel-parameters.txt | 3 +++ > include/linux/thread_info.h | 5 ++++ > mm/usercopy.c | 27 +++++++++++++++++++ > 4 files changed, 36 insertions(+) > > diff --git a/Documentation/admin-guide/kernel-parameters.rst b/Documentation/admin-guide/kernel-parameters.rst > index b8d0bc07ed0a..87a1200a1db6 100644 > --- a/Documentation/admin-guide/kernel-parameters.rst > +++ b/Documentation/admin-guide/kernel-parameters.rst > @@ -100,6 +100,7 @@ parameter is applicable:: > FB The frame buffer device is enabled. > FTRACE Function tracing enabled. > GCOV GCOV profiling is enabled. > + HUC Hardened usercopy is enabled > HW Appropriate hardware is enabled. > IA-64 IA-64 architecture is enabled. > IMA Integrity measurement architecture is enabled. > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index efc7aa7a0670..d14be0038aed 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -816,6 +816,9 @@ > disable= [IPV6] > See Documentation/networking/ipv6.txt. > > + disable_hardened_usercopy [HUC] > + Disable hardened usercopy checks > + > disable_radix [PPC] > Disable RADIX MMU mode on POWER9 > > diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h > index 8d8821b3689a..ab24fe2d3f87 100644 > --- a/include/linux/thread_info.h > +++ b/include/linux/thread_info.h > @@ -109,6 +109,11 @@ static inline int arch_within_stack_frames(const void * const stack, > #endif > > #ifdef CONFIG_HARDENED_USERCOPY > +#include > +#include > + > +DECLARE_STATIC_KEY_FALSE(bypass_usercopy_checks); > + > extern void __check_object_size(const void *ptr, unsigned long n, > bool to_user); > > diff --git a/mm/usercopy.c b/mm/usercopy.c > index e9e9325f7638..6a1265e1a54e 100644 > --- a/mm/usercopy.c > +++ b/mm/usercopy.c > @@ -20,6 +20,8 @@ > #include > #include > #include > +#include > +#include > #include > > /* > @@ -248,6 +250,9 @@ static inline void check_heap_object(const void *ptr, unsigned long n, > */ > void __check_object_size(const void *ptr, unsigned long n, bool to_user) > { > + if (static_branch_likely(&bypass_usercopy_checks)) > + return; > + > /* Skip all tests if size is zero. */ > if (!n) > return; > @@ -279,3 +284,25 @@ void __check_object_size(const void *ptr, unsigned long n, bool to_user) > check_kernel_text_object((const unsigned long)ptr, n, to_user); > } > EXPORT_SYMBOL(__check_object_size); > + > +DEFINE_STATIC_KEY_FALSE(bypass_usercopy_checks); > +EXPORT_SYMBOL(bypass_usercopy_checks); > + > +static bool disable_huc_atboot = false; > + > +static int __init parse_disable_usercopy(char *str) > +{ > + disable_huc_atboot = true; > + return 1; > +} > + > +static int __init set_disable_usercopy(void) > +{ > + if (disable_huc_atboot == true) > + static_branch_enable(&bypass_usercopy_checks); > + return 1; > +} > + > +__setup("disable_hardened_usercopy", parse_disable_usercopy); > + > +late_initcall(set_disable_usercopy);