From patchwork Fri Jan 20 16:41:25 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Garnier X-Patchwork-Id: 9528963 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 9111C601AE for ; Fri, 20 Jan 2017 16:42:10 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9A53828645 for ; Fri, 20 Jan 2017 16:42:10 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 8F00A28665; Fri, 20 Jan 2017 16:42:10 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.1 required=2.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED, RCVD_IN_DNSWL_MED, T_DKIM_INVALID autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id 7B48428645 for ; Fri, 20 Jan 2017 16:42:09 +0000 (UTC) Received: (qmail 20467 invoked by uid 550); 20 Jan 2017 16:42:03 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 20346 invoked from network); 20 Jan 2017 16:42:01 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=tcvCKygkcNZQWEwtWCtEONiUappuO+FauqqEUCIMUgQ=; b=V67CsDuPaBghXmFRmKakKX3tz3T+xqgADm3vK9ALFjKJeLU0bdblt3W2OrAPsJ7V3c +p1nC7HU6bzqViTJWuw4gOJahBVwWHd1FgcUSUxEqB1rXwOqSbsBZRA2tsGuVKfcnq8S afH0jl7kO8uFnaQ2J3Dh3zxCe+fm5Agob+dBo2Fr2fBUp7SDfBpMsHs51hMkXpECS7s3 0p+DEVrxo8cFhCA9YV5LFmLJGHuogIibtEcSY7XnLBB9YIzbUk9uqVurrp8oaTrI76bJ XhStVI+3Cz+JHMVDoFkL6rtGd/VsVPKCUuML99mHUMj679eEwCWJYahWvMPh2iPebGqX JL3w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=tcvCKygkcNZQWEwtWCtEONiUappuO+FauqqEUCIMUgQ=; b=PKkWvu900rhGoezy40Tqety5c8QBZJ6fXuWYo7yW1xxYH03rOqE0VfyWIzLiBDzMjN ZAlJ+J1w37cGy+cf8dyS44jwCmUSkmmkwLRFyJqGbBL2KxlGS37eAWmKTrTBE9BUv09I nKMXO6DFvfTUCNy1BLTN5U26wSNbzjRsHF3FrkC0NbX8D/ki/5GEDq9FY7+LJJ8qCjZK rtKLE37enp50Yplgb5vq1yus48zBm3nBuBI7cefPd3tCw7TlHfzWIqB4TurM+kYT+oWV gmSagji0I1kE0fP0Bjk5GX0Ob38pc2oU67YazdvvSSv65i7gGmB0Ct4Z+t7WT7zx3JeI iKXA== X-Gm-Message-State: AIkVDXIlhil00TsuW0A2ThV66N4662kzOCyEgPifkBk7JRBLLXlBayi7qelqJHCd4ij0/AQr X-Received: by 10.84.197.131 with SMTP id n3mr22599527pld.6.1484930509898; Fri, 20 Jan 2017 08:41:49 -0800 (PST) From: Thomas Garnier To: Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , Thomas Garnier , Kees Cook , "Rafael J . Wysocki" , Pavel Machek , Andy Lutomirski , Borislav Petkov , Christian Borntraeger , Brian Gerst , He Chen , Dave Hansen , Chen Yucong , Baoquan He , Paul Gortmaker , Joerg Roedel , Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , Fenghua Yu Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, kvm@vger.kernel.org, kernel-hardening@lists.openwall.com Date: Fri, 20 Jan 2017 08:41:25 -0800 Message-Id: <20170120164126.27624-2-thgarnie@google.com> X-Mailer: git-send-email 2.11.0.483.g087da7b7c-goog In-Reply-To: <20170120164126.27624-1-thgarnie@google.com> References: <20170120164126.27624-1-thgarnie@google.com> Subject: [kernel-hardening] [PATCH v1 2/3] x86: Remap GDT tables in the Fixmap section X-Virus-Scanned: ClamAV using ClamSMTP Each processor holds a GDT in its per-cpu structure. The sgdt instruction gives the base address of the current GDT. This address can be used to bypass KASLR memory randomization. With another bug, an attacker could target other per-cpu structures or deduce the base of the main memory section (PAGE_OFFSET). This patch relocates the GDT table for each processor inside the Fixmap section. The space is reserved based on number of supported cpus. For consistency, the remapping is done by default on 32 and 64 bit. Each processor switches to its remapped GDT at the end of initialization. For hibernation, the main processor returns with the original GDT and switches back to the remapping at completion. On 32 bit, the maximum number of processors is now 256. The Fixmap section cannot handle the original 512. Additional asserts ensure that the Fixmap section cannot grow beyond the space available. This patch was tested on both architectures. Hibernation and KVM were both tested specially for their usage of the GDT. Signed-off-by: Thomas Garnier --- Based on next-20170119 --- arch/x86/Kconfig | 1 + arch/x86/include/asm/fixmap.h | 4 ++++ arch/x86/include/asm/processor.h | 1 + arch/x86/kernel/cpu/common.c | 18 +++++++++++++++++- arch/x86/mm/init_32.c | 2 ++ arch/x86/power/cpu.c | 3 +++ 6 files changed, 28 insertions(+), 1 deletion(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index f1d4e8f2131f..b4ed35db10a8 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -912,6 +912,7 @@ config MAXSMP config NR_CPUS int "Maximum number of CPUs" if SMP && !MAXSMP range 2 8 if SMP && X86_32 && !X86_BIGSMP + range 2 256 if SMP && X86_32 && X86_BIGSMP range 2 512 if SMP && !MAXSMP && !CPUMASK_OFFSTACK range 2 8192 if SMP && !MAXSMP && CPUMASK_OFFSTACK && X86_64 default "1" if !SMP diff --git a/arch/x86/include/asm/fixmap.h b/arch/x86/include/asm/fixmap.h index c46289799b02..8b913b5e9383 100644 --- a/arch/x86/include/asm/fixmap.h +++ b/arch/x86/include/asm/fixmap.h @@ -100,6 +100,10 @@ enum fixed_addresses { #ifdef CONFIG_X86_INTEL_MID FIX_LNW_VRTC, #endif + /* Fixmap entries to remap the GDTs, one per processor. */ + FIX_GDT_REMAP_BEGIN, + FIX_GDT_REMAP_END = FIX_GDT_REMAP_BEGIN + NR_CPUS - 1, + __end_of_permanent_fixed_addresses, /* diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 1be64da0384e..280211ad8be9 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -705,6 +705,7 @@ extern struct desc_ptr early_gdt_descr; extern void cpu_set_gdt(int); extern void switch_to_new_gdt(int); +extern void load_remapped_gdt(int); extern void load_percpu_segment(int); extern void cpu_init(void); diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index e97ffc8d29f4..7d940b0e805a 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -443,6 +443,19 @@ void load_percpu_segment(int cpu) load_stack_canary_segment(); } +/* Load a fixmap remapping of the per-cpu GDT */ +void load_remapped_gdt(int cpu) +{ + struct desc_ptr gdt_descr; + unsigned long idx = FIX_GDT_REMAP_BEGIN + cpu; + + __set_fixmap(idx, __pa(get_cpu_gdt_table(cpu)), PAGE_KERNEL); + + gdt_descr.address = (long)__fix_to_virt(idx); + gdt_descr.size = GDT_SIZE - 1; + load_gdt(&gdt_descr); +} + /* * Current gdt points %fs at the "master" per-cpu area: after this, * it's on the real one. @@ -455,7 +468,6 @@ void switch_to_new_gdt(int cpu) gdt_descr.size = GDT_SIZE - 1; load_gdt(&gdt_descr); /* Reload the per-cpu base */ - load_percpu_segment(cpu); } @@ -1508,6 +1520,8 @@ void cpu_init(void) if (is_uv_system()) uv_cpu_init(); + + load_remapped_gdt(cpu); } #else @@ -1563,6 +1577,8 @@ void cpu_init(void) dbg_restore_debug_regs(); fpu__init_cpu(); + + load_remapped_gdt(cpu); } #endif diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c index 928d657de829..cfbcf42099d0 100644 --- a/arch/x86/mm/init_32.c +++ b/arch/x86/mm/init_32.c @@ -798,9 +798,11 @@ void __init mem_init(void) #ifdef CONFIG_HIGHMEM BUILD_BUG_ON(PKMAP_BASE + LAST_PKMAP*PAGE_SIZE > FIXADDR_START); BUILD_BUG_ON(VMALLOC_END > PKMAP_BASE); + BUILD_BUG_ON(__fix_to_virt(__end_of_fixed_addresses) <= PKMAP_BASE + LAST_PKMAP*PAGE_SIZE); #endif #define high_memory (-128UL << 20) BUILD_BUG_ON(VMALLOC_START >= VMALLOC_END); + BUILD_BUG_ON(__fix_to_virt(__end_of_fixed_addresses) <= VMALLOC_END); #undef high_memory #undef __FIXADDR_TOP diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c index 66ade16c7693..7578de6db833 100644 --- a/arch/x86/power/cpu.c +++ b/arch/x86/power/cpu.c @@ -183,6 +183,9 @@ static void fix_processor_context(void) load_mm_ldt(current->active_mm); /* This does lldt */ fpu__resume_cpu(); + + /* Load remapped GDT */ + load_remapped_gdt(cpu); } /**