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[209.132.180.67]) by mx.google.com with ESMTP id p21-v6si7194693pgd.56.2018.08.30.10.36.07; Thu, 30 Aug 2018 10:36:21 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=vmware.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727682AbeH3Vhq (ORCPT + 99 others); Thu, 30 Aug 2018 17:37:46 -0400 Received: from ex13-edg-ou-001.vmware.com ([208.91.0.189]:48535 "EHLO EX13-EDG-OU-001.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727129AbeH3VhT (ORCPT ); Thu, 30 Aug 2018 17:37:19 -0400 Received: from sc9-mailhost2.vmware.com (10.113.161.72) by EX13-EDG-OU-001.vmware.com (10.113.208.155) with Microsoft SMTP Server id 15.0.1156.6; Thu, 30 Aug 2018 10:33:48 -0700 Received: from sc2-haas01-esx0118.eng.vmware.com (sc2-haas01-esx0118.eng.vmware.com [10.172.44.118]) by sc9-mailhost2.vmware.com (Postfix) with ESMTP id AC5B5B05DE; Thu, 30 Aug 2018 13:34:06 -0400 (EDT) From: Nadav Amit To: Thomas Gleixner CC: , Ingo Molnar , , Arnd Bergmann , , Dave Hansen , Nadav Amit , Masami Hiramatsu , Kees Cook , Peter Zijlstra , Dave Hansen Subject: [PATCH 4/6] x86/alternatives: initializing temporary mm for patching Date: Thu, 30 Aug 2018 10:32:16 -0700 Message-ID: <20180830173218.238900-5-namit@vmware.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20180830173218.238900-1-namit@vmware.com> References: <20180830173218.238900-1-namit@vmware.com> MIME-Version: 1.0 Content-Type: text/plain Received-SPF: None (EX13-EDG-OU-001.vmware.com: namit@vmware.com does not designate permitted sender hosts) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org To prevent improper use of the PTEs that are used for text patching, we want to use a temporary mm struct. We initailize it by copying the init mm. The address that will be used for patching is taken from the lower area that is usually used for the task memory. Doing so prevents the need to frequently synchronize the temporary-mm (e.g., when BPF programs are installed), since different PGDs are used for the task memory. Finally, we randomize the address of the PTEs to harden against exploits that use these PTEs. Cc: Masami Hiramatsu Cc: Kees Cook Cc: Peter Zijlstra Cc: Dave Hansen Suggested-by: Andy Lutomirski Signed-off-by: Nadav Amit --- arch/x86/include/asm/pgtable.h | 3 +++ arch/x86/include/asm/text-patching.h | 2 ++ arch/x86/mm/init_64.c | 29 ++++++++++++++++++++++++++++ init/main.c | 3 +++ 4 files changed, 37 insertions(+) diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index e4ffa565a69f..3de9a1fb7a9a 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -1022,6 +1022,9 @@ static inline void __meminit init_trampoline_default(void) /* Default trampoline pgd value */ trampoline_pgd_entry = init_top_pgt[pgd_index(__PAGE_OFFSET)]; } + +void __init poking_init(void); + # ifdef CONFIG_RANDOMIZE_MEMORY void __meminit init_trampoline(void); # else diff --git a/arch/x86/include/asm/text-patching.h b/arch/x86/include/asm/text-patching.h index e85ff65c43c3..ffe7902cc326 100644 --- a/arch/x86/include/asm/text-patching.h +++ b/arch/x86/include/asm/text-patching.h @@ -38,5 +38,7 @@ extern void *text_poke(void *addr, const void *opcode, size_t len); extern int poke_int3_handler(struct pt_regs *regs); extern void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler); extern int after_bootmem; +extern __ro_after_init struct mm_struct *poking_mm; +extern __ro_after_init unsigned long poking_addr; #endif /* _ASM_X86_TEXT_PATCHING_H */ diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index dd519f372169..db33a724a054 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -54,6 +54,7 @@ #include #include #include +#include #include "mm_internal.h" @@ -1389,6 +1390,34 @@ unsigned long memory_block_size_bytes(void) return memory_block_size_probed; } +/* + * Initialize an mm_struct to be used during poking and a pointer to be used + * during patching. If anything fails during initialization, poking will be done + * using the fixmap, which is unsafe, so warn the user about it. + */ +void __init poking_init(void) +{ + unsigned long poking_addr; + + poking_mm = copy_init_mm(); + if (!poking_mm) { + pr_err("x86/mm: error setting a separate poking address space"); + return; + } + + /* + * Randomize the poking address, but make sure that the following page + * will be mapped at the same PMD. We need 2 pages, so find space for 3, + * and adjust the address if the PMD ends after the first one. + */ + poking_addr = TASK_UNMAPPED_BASE + + (kaslr_get_random_long("Poking") & PAGE_MASK) % + (TASK_SIZE - TASK_UNMAPPED_BASE - 3 * PAGE_SIZE); + + if (((poking_addr + PAGE_SIZE) & ~PMD_MASK) == 0) + poking_addr += PAGE_SIZE; +} + #ifdef CONFIG_SPARSEMEM_VMEMMAP /* * Initialise the sparsemem vmemmap using huge-pages at the PMD level. diff --git a/init/main.c b/init/main.c index 18f8f0140fa0..8c6dd8d88fca 100644 --- a/init/main.c +++ b/init/main.c @@ -496,6 +496,8 @@ void __init __weak thread_stack_cache_init(void) void __init __weak mem_encrypt_init(void) { } +void __init __weak poking_init(void) { } + bool initcall_debug; core_param(initcall_debug, initcall_debug, bool, 0644); @@ -725,6 +727,7 @@ asmlinkage __visible void __init start_kernel(void) taskstats_init_early(); delayacct_init(); + poking_init(); check_bugs(); acpi_subsystem_init(); -- 2.17.1