From patchwork Tue Oct 23 21:34:49 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Igor Stoppa X-Patchwork-Id: 10653723 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 30EFC13A4 for ; Tue, 23 Oct 2018 21:36:40 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 1D00B2A3CD for ; Tue, 23 Oct 2018 21:36:40 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 113962A3D3; Tue, 23 Oct 2018 21:36:40 +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=-5.0 required=2.0 tests=BAYES_00,DKIM_ADSP_CUSTOM_MED, DKIM_INVALID,DKIM_SIGNED,FREEMAIL_FROM,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED 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 80F222A3CD for ; Tue, 23 Oct 2018 21:36:38 +0000 (UTC) Received: (qmail 13555 invoked by uid 550); 23 Oct 2018 21:36:12 -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 13498 invoked from network); 23 Oct 2018 21:36:11 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references:reply-to; bh=lWr5dc2eNvTcJb+c+uRTUJwhKcPYmmWV6t14BAAM0+g=; b=K5HssUtWyqhs3CTyKNXHpefeYDtWkJbXaAX1XLxON4iECRSRB6QjMc5RCzYk0y3yfd 3c1iOvdGFcidkqsyYIElslGkPelZCRE/JLn4hSqqkZH2OH3h57NZu/YFoNNNAjmaYHMg 36urDvGuUDvpjx00WQrlW9VtHoMHr8CdHjsfQij3WvBYK3waVusZpw/gnqTE7YAg+T8z SO7hquz3XCCU2aYUVW1L7jBQGaZliOW0tEQjX97ZIN9jZwLllZqgweeeNE0Lm7lP2AZN mpclQP5Np4932IIJTLzPM1PMBsppoxoRMBjfYYZLQ0qprQKK8NxeH80SI6RaTIOohnqU wQQA== 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:reply-to; bh=lWr5dc2eNvTcJb+c+uRTUJwhKcPYmmWV6t14BAAM0+g=; b=P7Oqufm8FdK92O95G2j7Rf+11lQ2IAdPGuUEt07e3dtIqKuLv5YrxlvfYZ2t5eT06q o6bUvoIb4UiwkVY3lt5HniUIr28tWGVV5GWf9QOY5oGa1Bi+OW484Qcje1Yynyip9lhd /0mm9WiiK7MFlmARm4Jocx03k5HJ0sjRGs1F41y1G7G6fLkfPCoIR7gTl6iBLzRxA3wt DASyNLlB1DHOoWxe9JXT2Dc0T1saz+ZK3/Xo+7CO8/+zmKAbrnwuO6mXooFGjcNxtNJu utXf71iAGFRmgoUSG4A0NcZS/u/GS8eZ7kINeA1SbF2TymxNnh88J+VxTQfP869hFvCV vXuQ== X-Gm-Message-State: ABuFfoh8rnNDERwrr5zjLo8DQxG1U3NEyEvTOU4LtMS+9QuPgD6TnQ06 ba5qnwgjjT8v6XWLAeBO6qA= X-Google-Smtp-Source: ACcGV63HspKtXzSwNphXjTw4U5KnYFl/LeBjRKri4bDR8FgHFnbdnJMdM8PgkfyEiZhsocjgUN4K2w== X-Received: by 2002:a19:2648:: with SMTP id m69-v6mr12821527lfm.78.1540330559911; Tue, 23 Oct 2018 14:35:59 -0700 (PDT) From: Igor Stoppa X-Google-Original-From: Igor Stoppa To: Mimi Zohar , Kees Cook , Matthew Wilcox , Dave Chinner , James Morris , Michal Hocko , kernel-hardening@lists.openwall.com, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org Cc: igor.stoppa@huawei.com, Dave Hansen , Jonathan Corbet , Laura Abbott , Vlastimil Babka , "Kirill A. Shutemov" , Andrew Morton , Pavel Tatashin , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH 02/17] prmem: write rare for static allocation Date: Wed, 24 Oct 2018 00:34:49 +0300 Message-Id: <20181023213504.28905-3-igor.stoppa@huawei.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20181023213504.28905-1-igor.stoppa@huawei.com> References: <20181023213504.28905-1-igor.stoppa@huawei.com> X-Virus-Scanned: ClamAV using ClamSMTP Implementation of write rare for statically allocated data, located in a specific memory section through the use of the __write_rare label. The basic functions are wr_memcpy() and wr_memset(): the write rare counterparts of memcpy() and memset() respectively. To minimize chances of attacks, this implementation does not unprotect existing memory pages. Instead, it remaps them, one by one, at random free locations, as writable. Each page is mapped as writable strictly for the time needed to perform changes in said page. While a page is remapped, interrupts are disabled on the core performing the write rare operation, to avoid being frozen mid-air by an attack using interrupts for stretching the duration of the alternate mapping. OTOH, to avoid introducing unpredictable delays, the interrupts are re-enabled inbetween page remapping, when write operations are either completed or not yet started, and there is not alternate, writable mapping to exploit. Signed-off-by: Igor Stoppa CC: Michal Hocko CC: Vlastimil Babka CC: "Kirill A. Shutemov" CC: Andrew Morton CC: Pavel Tatashin CC: linux-mm@kvack.org CC: linux-kernel@vger.kernel.org --- MAINTAINERS | 7 ++ include/linux/prmem.h | 213 ++++++++++++++++++++++++++++++++++++++++++ mm/Makefile | 1 + mm/prmem.c | 10 ++ 4 files changed, 231 insertions(+) create mode 100644 include/linux/prmem.h create mode 100644 mm/prmem.c diff --git a/MAINTAINERS b/MAINTAINERS index b2f710eee67a..e566c5d09faf 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -9454,6 +9454,13 @@ F: kernel/sched/membarrier.c F: include/uapi/linux/membarrier.h F: arch/powerpc/include/asm/membarrier.h +MEMORY HARDENING +M: Igor Stoppa +L: kernel-hardening@lists.openwall.com +S: Maintained +F: include/linux/prmem.h +F: mm/prmem.c + MEMORY MANAGEMENT L: linux-mm@kvack.org W: http://www.linux-mm.org diff --git a/include/linux/prmem.h b/include/linux/prmem.h new file mode 100644 index 000000000000..3ba41d76a582 --- /dev/null +++ b/include/linux/prmem.h @@ -0,0 +1,213 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * prmem.h: Header for memory protection library + * + * (C) Copyright 2018 Huawei Technologies Co. Ltd. + * Author: Igor Stoppa + * + * Support for: + * - statically allocated write rare data + */ + +#ifndef _LINUX_PRMEM_H +#define _LINUX_PRMEM_H + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +/* ============================ Write Rare ============================ */ + +extern const char WR_ERR_RANGE_MSG[]; +extern const char WR_ERR_PAGE_MSG[]; + +/* + * The following two variables are statically allocated by the linker + * script at the the boundaries of the memory region (rounded up to + * multiples of PAGE_SIZE) reserved for __wr_after_init. + */ +extern long __start_wr_after_init; +extern long __end_wr_after_init; + +static __always_inline bool __is_wr_after_init(const void *ptr, size_t size) +{ + size_t start = (size_t)&__start_wr_after_init; + size_t end = (size_t)&__end_wr_after_init; + size_t low = (size_t)ptr; + size_t high = (size_t)ptr + size; + + return likely(start <= low && low < high && high <= end); +} + +/** + * wr_memset() - sets n bytes of the destination to the c value + * @dst: beginning of the memory to write to + * @c: byte to replicate + * @size: amount of bytes to copy + * + * Returns true on success, false otherwise. + */ +static __always_inline +bool wr_memset(const void *dst, const int c, size_t n_bytes) +{ + size_t size; + unsigned long flags; + uintptr_t d = (uintptr_t)dst; + + if (WARN(!__is_wr_after_init(dst, n_bytes), WR_ERR_RANGE_MSG)) + return false; + while (n_bytes) { + struct page *page; + uintptr_t base; + uintptr_t offset; + uintptr_t offset_complement; + + local_irq_save(flags); + page = virt_to_page(d); + offset = d & ~PAGE_MASK; + offset_complement = PAGE_SIZE - offset; + size = min(n_bytes, offset_complement); + base = (uintptr_t)vmap(&page, 1, VM_MAP, PAGE_KERNEL); + if (WARN(!base, WR_ERR_PAGE_MSG)) { + local_irq_restore(flags); + return false; + } + memset((void *)(base + offset), c, size); + vunmap((void *)base); + d += size; + n_bytes -= size; + local_irq_restore(flags); + } + return true; +} + +/** + * wr_memcpy() - copyes n bytes from source to destination + * @dst: beginning of the memory to write to + * @src: beginning of the memory to read from + * @n_bytes: amount of bytes to copy + * + * Returns true on success, false otherwise. + */ +static __always_inline +bool wr_memcpy(const void *dst, const void *src, size_t n_bytes) +{ + size_t size; + unsigned long flags; + uintptr_t d = (uintptr_t)dst; + uintptr_t s = (uintptr_t)src; + + if (WARN(!__is_wr_after_init(dst, n_bytes), WR_ERR_RANGE_MSG)) + return false; + while (n_bytes) { + struct page *page; + uintptr_t base; + uintptr_t offset; + uintptr_t offset_complement; + + local_irq_save(flags); + page = virt_to_page(d); + offset = d & ~PAGE_MASK; + offset_complement = PAGE_SIZE - offset; + size = (size_t)min(n_bytes, offset_complement); + base = (uintptr_t)vmap(&page, 1, VM_MAP, PAGE_KERNEL); + if (WARN(!base, WR_ERR_PAGE_MSG)) { + local_irq_restore(flags); + return false; + } + __write_once_size((void *)(base + offset), (void *)s, size); + vunmap((void *)base); + d += size; + s += size; + n_bytes -= size; + local_irq_restore(flags); + } + return true; +} + +/* + * rcu_assign_pointer is a macro, which takes advantage of being able to + * take the address of the destination parameter "p", so that it can be + * passed to WRITE_ONCE(), which is called in one of the branches of + * rcu_assign_pointer() and also, being a macro, can rely on the + * preprocessor for taking the address of its parameter. + * For the sake of staying compatible with the API, also + * wr_rcu_assign_pointer() is a macro that accepts a pointer as parameter, + * instead of the address of said pointer. + * However it is simply a wrapper to __wr_rcu_ptr(), which receives the + * address of the pointer. + */ +static __always_inline +uintptr_t __wr_rcu_ptr(const void *dst_p_p, const void *src_p) +{ + unsigned long flags; + struct page *page; + void *base; + uintptr_t offset; + const size_t size = sizeof(void *); + + if (WARN(!__is_wr_after_init(dst_p_p, size), WR_ERR_RANGE_MSG)) + return (uintptr_t)NULL; + local_irq_save(flags); + page = virt_to_page(dst_p_p); + offset = (uintptr_t)dst_p_p & ~PAGE_MASK; + base = vmap(&page, 1, VM_MAP, PAGE_KERNEL); + if (WARN(!base, WR_ERR_PAGE_MSG)) { + local_irq_restore(flags); + return (uintptr_t)NULL; + } + rcu_assign_pointer((*(void **)(offset + (uintptr_t)base)), src_p); + vunmap(base); + local_irq_restore(flags); + return (uintptr_t)src_p; +} + +#define wr_rcu_assign_pointer(p, v) __wr_rcu_ptr(&p, v) + +#define __wr_simple(dst_ptr, src_ptr) \ + wr_memcpy(dst_ptr, src_ptr, sizeof(*(src_ptr))) + +#define __wr_safe(dst_ptr, src_ptr, \ + unique_dst_ptr, unique_src_ptr) \ +({ \ + typeof(dst_ptr) unique_dst_ptr = (dst_ptr); \ + typeof(src_ptr) unique_src_ptr = (src_ptr); \ + \ + wr_memcpy(unique_dst_ptr, unique_src_ptr, \ + sizeof(*(unique_src_ptr))); \ +}) + +#define __safe_ops(dst, src) \ + (__typecheck(dst, src) && __no_side_effects(dst, src)) + +/** + * wr - copies an object over another of same type and size + * @dst_ptr: address of the destination object + * @src_ptr: address of the source object + */ +#define wr(dst_ptr, src_ptr) \ + __builtin_choose_expr(__safe_ops(dst_ptr, src_ptr), \ + __wr_simple(dst_ptr, src_ptr), \ + __wr_safe(dst_ptr, src_ptr, \ + __UNIQUE_ID(__dst_ptr), \ + __UNIQUE_ID(__src_ptr))) + +/** + * wr_ptr() - alters a pointer in write rare memory + * @dst: target for write + * @val: new value + * + * Returns true on success, false otherwise. + */ +static __always_inline +bool wr_ptr(const void *dst, const void *val) +{ + return wr_memcpy(dst, &val, sizeof(val)); +} +#endif diff --git a/mm/Makefile b/mm/Makefile index 26ef77a3883b..215c6a6d7304 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -64,6 +64,7 @@ obj-$(CONFIG_SPARSEMEM) += sparse.o obj-$(CONFIG_SPARSEMEM_VMEMMAP) += sparse-vmemmap.o obj-$(CONFIG_SLOB) += slob.o obj-$(CONFIG_MMU_NOTIFIER) += mmu_notifier.o +obj-$(CONFIG_PRMEM) += prmem.o obj-$(CONFIG_KSM) += ksm.o obj-$(CONFIG_PAGE_POISONING) += page_poison.o obj-$(CONFIG_SLAB) += slab.o diff --git a/mm/prmem.c b/mm/prmem.c new file mode 100644 index 000000000000..de9258f5f29a --- /dev/null +++ b/mm/prmem.c @@ -0,0 +1,10 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * prmem.c: Memory Protection Library + * + * (C) Copyright 2017-2018 Huawei Technologies Co. Ltd. + * Author: Igor Stoppa + */ + +const char WR_ERR_RANGE_MSG[] = "Write rare on invalid memory range."; +const char WR_ERR_PAGE_MSG[] = "Failed to remap write rare page.";