From patchwork Mon Jul 27 16:29:31 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mike Rapoport X-Patchwork-Id: 11687187 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 5F0306C1 for ; Mon, 27 Jul 2020 16:30:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 396C42078A for ; Mon, 27 Jul 2020 16:30:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595867418; bh=nwPr1m6QwakaD96Vicd58BMyOzSimKClw0mUV6BuDKU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=ecEhuLHQ7U5S8N1pypTZlMSFtRMGJdWqUKDvvxhFhu0Ri0Y3Gw1BZSXj59T9m4qAh 33gNBkWd2XtN8hYWf9VKc8ToQ2U56UuzzYOn4YGbQ2mJD/xTWn/CRaAlC4qM275IUC N+vniW/x2d8sGAie3HlJ2zfhsJPp2wgI3bcyIaRM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731223AbgG0QaO (ORCPT ); Mon, 27 Jul 2020 12:30:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:58878 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730759AbgG0QaO (ORCPT ); Mon, 27 Jul 2020 12:30:14 -0400 Received: from aquarius.haifa.ibm.com (nesher1.haifa.il.ibm.com [195.110.40.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 7A1FA20719; Mon, 27 Jul 2020 16:30:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595867412; bh=nwPr1m6QwakaD96Vicd58BMyOzSimKClw0mUV6BuDKU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=J6NnfAGgxq3XeXeTz9P9N9swbf0NhSdVT+EQ7g7i3FWsrmPpjLjhCnAc7U81DhJFh 3EPPAkR74gNItRp66nDuluA6QBm9s0vk0ZgVRJDaqYXViOY5KLMPHswRoneGmQWGVL 7C+xLocl7uFkWKwY+YehCsQAUm+Lp5YzbEmSwKvc= From: Mike Rapoport To: linux-kernel@vger.kernel.org Cc: Alexander Viro , Andrew Morton , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Catalin Marinas , Christopher Lameter , Dan Williams , Dave Hansen , Elena Reshetova , "H. Peter Anvin" , Idan Yaniv , Ingo Molnar , James Bottomley , "Kirill A. Shutemov" , Matthew Wilcox , Mike Rapoport , Mike Rapoport , Michael Kerrisk , Palmer Dabbelt , Paul Walmsley , Peter Zijlstra , Thomas Gleixner , Tycho Andersen , Will Deacon , linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@lists.01.org, linux-riscv@lists.infradead.org, x86@kernel.org Subject: [PATCH v2 3/7] mm: introduce memfd_secret system call to create "secret" memory areas Date: Mon, 27 Jul 2020 19:29:31 +0300 Message-Id: <20200727162935.31714-4-rppt@kernel.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200727162935.31714-1-rppt@kernel.org> References: <20200727162935.31714-1-rppt@kernel.org> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Mike Rapoport Introduce "memfd_secret" system call with the ability to create memory areas visible only in the context of the owning process and not mapped not only to other processes but in the kernel page tables as well. The user will create a file descriptor using the memfd_secret() system call where flags supplied as a parameter to this system call will define the desired protection mode for the memory associated with that file descriptor. Currently there are two protection modes: * exclusive - the memory area is unmapped from the kernel direct map and it is present only in the page tables of the owning mm. * uncached - the memory area is present only in the page tables of the owning mm and it is mapped there as uncached. For instance, the following example will create an uncached mapping (error handling is omitted): fd = memfd_secret(SECRETMEM_UNCACHED); ftruncate(fd, MAP_SIZE); ptr = mmap(NULL, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); Signed-off-by: Mike Rapoport --- include/uapi/linux/magic.h | 1 + include/uapi/linux/secretmem.h | 9 ++ kernel/sys_ni.c | 2 + mm/Kconfig | 4 + mm/Makefile | 1 + mm/secretmem.c | 266 +++++++++++++++++++++++++++++++++ 6 files changed, 283 insertions(+) create mode 100644 include/uapi/linux/secretmem.h create mode 100644 mm/secretmem.c diff --git a/include/uapi/linux/magic.h b/include/uapi/linux/magic.h index f3956fc11de6..35687dcb1a42 100644 --- a/include/uapi/linux/magic.h +++ b/include/uapi/linux/magic.h @@ -97,5 +97,6 @@ #define DEVMEM_MAGIC 0x454d444d /* "DMEM" */ #define Z3FOLD_MAGIC 0x33 #define PPC_CMM_MAGIC 0xc7571590 +#define SECRETMEM_MAGIC 0x5345434d /* "SECM" */ #endif /* __LINUX_MAGIC_H__ */ diff --git a/include/uapi/linux/secretmem.h b/include/uapi/linux/secretmem.h new file mode 100644 index 000000000000..cef7a59f7492 --- /dev/null +++ b/include/uapi/linux/secretmem.h @@ -0,0 +1,9 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +#ifndef _UAPI_LINUX_SECRERTMEM_H +#define _UAPI_LINUX_SECRERTMEM_H + +/* secretmem operation modes */ +#define SECRETMEM_EXCLUSIVE 0x1 +#define SECRETMEM_UNCACHED 0x2 + +#endif /* _UAPI_LINUX_SECRERTMEM_H */ diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c index 3b69a560a7ac..fd40e1c083e5 100644 --- a/kernel/sys_ni.c +++ b/kernel/sys_ni.c @@ -349,6 +349,8 @@ COND_SYSCALL(pkey_mprotect); COND_SYSCALL(pkey_alloc); COND_SYSCALL(pkey_free); +/* memfd_secret */ +COND_SYSCALL(memfd_secret); /* * Architecture specific weak syscall entries. diff --git a/mm/Kconfig b/mm/Kconfig index f2104cc0d35c..8378175e72a4 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -872,4 +872,8 @@ config ARCH_HAS_HUGEPD config MAPPING_DIRTY_HELPERS bool +config SECRETMEM + def_bool ARCH_HAS_SET_DIRECT_MAP && !EMBEDDED + select GENERIC_ALLOCATOR + endmenu diff --git a/mm/Makefile b/mm/Makefile index 6e9d46b2efc9..c2aa7a393b73 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -121,3 +121,4 @@ obj-$(CONFIG_MEMFD_CREATE) += memfd.o obj-$(CONFIG_MAPPING_DIRTY_HELPERS) += mapping_dirty_helpers.o obj-$(CONFIG_PTDUMP_CORE) += ptdump.o obj-$(CONFIG_PAGE_REPORTING) += page_reporting.o +obj-$(CONFIG_SECRETMEM) += secretmem.o diff --git a/mm/secretmem.c b/mm/secretmem.c new file mode 100644 index 000000000000..9d29f3e1c49d --- /dev/null +++ b/mm/secretmem.c @@ -0,0 +1,266 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#include + +#include + +#include "internal.h" + +#undef pr_fmt +#define pr_fmt(fmt) "secretmem: " fmt + +#define SECRETMEM_MODE_MASK (SECRETMEM_EXCLUSIVE | SECRETMEM_UNCACHED) +#define SECRETMEM_FLAGS_MASK SECRETMEM_MODE_MASK + +struct secretmem_ctx { + unsigned int mode; +}; + +static struct page *secretmem_alloc_page(gfp_t gfp) +{ + /* + * FIXME: use a cache of large pages to reduce the direct map + * fragmentation + */ + return alloc_page(gfp); +} + +static vm_fault_t secretmem_fault(struct vm_fault *vmf) +{ + struct address_space *mapping = vmf->vma->vm_file->f_mapping; + struct inode *inode = file_inode(vmf->vma->vm_file); + pgoff_t offset = vmf->pgoff; + unsigned long addr; + struct page *page; + int ret = 0; + + if (((loff_t)vmf->pgoff << PAGE_SHIFT) >= i_size_read(inode)) + return vmf_error(-EINVAL); + + page = find_get_entry(mapping, offset); + if (!page) { + page = secretmem_alloc_page(vmf->gfp_mask); + if (!page) + return vmf_error(-ENOMEM); + + ret = add_to_page_cache(page, mapping, offset, vmf->gfp_mask); + if (unlikely(ret)) + goto err_put_page; + + ret = set_direct_map_invalid_noflush(page); + if (ret) + goto err_del_page_cache; + + addr = (unsigned long)page_address(page); + flush_tlb_kernel_range(addr, addr + PAGE_SIZE); + + __SetPageUptodate(page); + + ret = VM_FAULT_LOCKED; + } + + vmf->page = page; + return ret; + +err_del_page_cache: + delete_from_page_cache(page); +err_put_page: + put_page(page); + return vmf_error(ret); +} + +static const struct vm_operations_struct secretmem_vm_ops = { + .fault = secretmem_fault, +}; + +static int secretmem_mmap(struct file *file, struct vm_area_struct *vma) +{ + struct secretmem_ctx *ctx = file->private_data; + unsigned long mode = ctx->mode; + unsigned long len = vma->vm_end - vma->vm_start; + + if (!mode) + return -EINVAL; + + if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0) + return -EINVAL; + + if (mlock_future_check(vma->vm_mm, vma->vm_flags | VM_LOCKED, len)) + return -EAGAIN; + + switch (mode) { + case SECRETMEM_UNCACHED: + vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot); + fallthrough; + case SECRETMEM_EXCLUSIVE: + vma->vm_ops = &secretmem_vm_ops; + break; + default: + return -EINVAL; + } + + vma->vm_flags |= VM_LOCKED; + + return 0; +} + +const struct file_operations secretmem_fops = { + .mmap = secretmem_mmap, +}; + +static bool secretmem_isolate_page(struct page *page, isolate_mode_t mode) +{ + return false; +} + +static int secretmem_migratepage(struct address_space *mapping, + struct page *newpage, struct page *page, + enum migrate_mode mode) +{ + return -EBUSY; +} + +static void secretmem_freepage(struct page *page) +{ + set_direct_map_default_noflush(page); +} + +static const struct address_space_operations secretmem_aops = { + .freepage = secretmem_freepage, + .migratepage = secretmem_migratepage, + .isolate_page = secretmem_isolate_page, +}; + +static struct vfsmount *secretmem_mnt; + +static struct file *secretmem_file_create(unsigned long flags) +{ + struct file *file = ERR_PTR(-ENOMEM); + struct secretmem_ctx *ctx; + struct inode *inode; + + inode = alloc_anon_inode(secretmem_mnt->mnt_sb); + if (IS_ERR(inode)) + return ERR_CAST(inode); + + ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); + if (!ctx) + goto err_free_inode; + + file = alloc_file_pseudo(inode, secretmem_mnt, "secretmem", + O_RDWR, &secretmem_fops); + if (IS_ERR(file)) + goto err_free_ctx; + + mapping_set_unevictable(inode->i_mapping); + + inode->i_mapping->private_data = ctx; + inode->i_mapping->a_ops = &secretmem_aops; + + /* pretend we are a normal file with zero size */ + inode->i_mode |= S_IFREG; + inode->i_size = 0; + + file->private_data = ctx; + + ctx->mode = flags & SECRETMEM_MODE_MASK; + + return file; + +err_free_ctx: + kfree(ctx); +err_free_inode: + iput(inode); + return file; +} + +SYSCALL_DEFINE1(memfd_secret, unsigned long, flags) +{ + struct file *file; + unsigned int mode; + int fd, err; + + /* make sure local flags do not confict with global fcntl.h */ + BUILD_BUG_ON(SECRETMEM_FLAGS_MASK & O_CLOEXEC); + + if (flags & ~(SECRETMEM_FLAGS_MASK | O_CLOEXEC)) + return -EINVAL; + + /* modes are mutually exclusive, only one mode bit should be set */ + mode = flags & SECRETMEM_FLAGS_MASK; + if (ffs(mode) != fls(mode)) + return -EINVAL; + + fd = get_unused_fd_flags(flags & O_CLOEXEC); + if (fd < 0) + return fd; + + file = secretmem_file_create(flags); + if (IS_ERR(file)) { + err = PTR_ERR(file); + goto err_put_fd; + } + + file->f_flags |= O_LARGEFILE; + + fd_install(fd, file); + return fd; + +err_put_fd: + put_unused_fd(fd); + return err; +} + +static void secretmem_evict_inode(struct inode *inode) +{ + struct secretmem_ctx *ctx = inode->i_private; + + truncate_inode_pages_final(&inode->i_data); + clear_inode(inode); + kfree(ctx); +} + +static const struct super_operations secretmem_super_ops = { + .evict_inode = secretmem_evict_inode, +}; + +static int secretmem_init_fs_context(struct fs_context *fc) +{ + struct pseudo_fs_context *ctx = init_pseudo(fc, SECRETMEM_MAGIC); + + if (!ctx) + return -ENOMEM; + ctx->ops = &secretmem_super_ops; + + return 0; +} + +static struct file_system_type secretmem_fs = { + .name = "secretmem", + .init_fs_context = secretmem_init_fs_context, + .kill_sb = kill_anon_super, +}; + +static int secretmem_init(void) +{ + int ret = 0; + + secretmem_mnt = kern_mount(&secretmem_fs); + if (IS_ERR(secretmem_mnt)) + ret = PTR_ERR(secretmem_mnt); + + return ret; +} +fs_initcall(secretmem_init);