From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B3164FA373D for ; Thu, 27 Oct 2022 10:21:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234717AbiJ0KVv (ORCPT ); Thu, 27 Oct 2022 06:21:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43952 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234812AbiJ0KVk (ORCPT ); Thu, 27 Oct 2022 06:21:40 -0400 Received: from mail-lf1-x131.google.com (mail-lf1-x131.google.com [IPv6:2a00:1450:4864:20::131]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5050A57559 for ; Thu, 27 Oct 2022 03:21:36 -0700 (PDT) Received: by mail-lf1-x131.google.com with SMTP id j16so1775506lfe.12 for ; Thu, 27 Oct 2022 03:21:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=xZ3dt0X5oEa9EitEEQpoTk/uun4esw3O+yAdY14ujzY=; b=UJe3W3C7PYf+7aofEnbgK9L1qF/5znWnv5kKpBPzv+GKCTzcpPqVHyNc/PLAMaqQgt 9q/ylrlPYrog9Oi55ScgA6DJd3bGihyqQtnVdaxcT34P/TuDFa0LxptXPuN72g5xPbaG Hn+EEF10aYfiVyTmFM1jJTkMiMNO4QwTw/9rIvbEg/1aDPHA6HrSMnu2tnwrxjCORUXy 2Et52nUNOcRHlZiyMHqSTKaOMoqlkmiLqrE4e4zDJkLYPp+FoMx7C3LNKhrY5LHDouNN d/NMim4+Awu3Gi0UMj7WcI0vUTs5qv/qB+M9nDkJLIMb0he9k4beLsrGOt3aa81oyPOV LLZg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=xZ3dt0X5oEa9EitEEQpoTk/uun4esw3O+yAdY14ujzY=; b=o/EHUldNFk3GvZYvp6gNm5azqNmTADYBooa1oaAme8MtQ4p9JAxFohVDQZIVSZPX8F HCBM9dZ4eYR7oa8MKoV51P8T91lJ4mNAiuEpxo3EncNkCdpPZM6FlpfddLZh/Gh7Kmwy QT/hjMvomIiS6kKxtR9mwVQHZ7t4kTy9QHq56mRYXi+g4AdjcA14GXNYVAJ4wJWvEDCA tDyPvQ3fKRqpO+dMVcFx+bZ+gnhHYPQfCVVrnkvjmjb6JjiLdxikkyzFVeQnZMpGlwMV O1pUsAdGH9N+Tm/1VHSDV15Rq2ZLJqJ6CaHhBytdE1Eeg7Nh1Qdc5eYq+ooYXeJATE2U izBg== X-Gm-Message-State: ACrzQf3He0YsAO3BLH4D63hkU05a+bpjUG+zmutFC979a9c76Lyndi5g AXBSYWQ3K02Knw+VRVUTai3Pe478xRsTOAz5PX6s5g== X-Google-Smtp-Source: AMsMyM5Fe2p29tDglku84UTHrEJvMRQgfKovUuWsBkEAzfOu+0McYs3xjNPk1oitcyOLEQbvJVm7whYBF/OM9LUBds8= X-Received: by 2002:a05:6512:2392:b0:4a2:550a:e21d with SMTP id c18-20020a056512239200b004a2550ae21dmr18987300lfv.550.1666866094379; Thu, 27 Oct 2022 03:21:34 -0700 (PDT) MIME-Version: 1.0 References: <20221025151344.3784230-1-chao.p.peng@linux.intel.com> <20221025151344.3784230-2-chao.p.peng@linux.intel.com> In-Reply-To: <20221025151344.3784230-2-chao.p.peng@linux.intel.com> From: Fuad Tabba Date: Thu, 27 Oct 2022 11:20:57 +0100 Message-ID: Subject: Re: [PATCH v9 1/8] mm: Introduce memfd_restricted system call to create restricted user memory To: Chao Peng Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, linux-doc@vger.kernel.org, qemu-devel@nongnu.org, Paolo Bonzini , Jonathan Corbet , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H . Peter Anvin" , Hugh Dickins , Jeff Layton , "J . Bruce Fields" , Andrew Morton , Shuah Khan , Mike Rapoport , Steven Price , "Maciej S . Szmigiero" , Vlastimil Babka , Vishal Annapurve , Yu Zhang , "Kirill A . Shutemov" , luto@kernel.org, jun.nakajima@intel.com, dave.hansen@intel.com, ak@linux.intel.com, david@redhat.com, aarcange@redhat.com, ddutile@redhat.com, dhildenb@redhat.com, Quentin Perret , Michael Roth , mhocko@suse.com, Muchun Song , wei.w.wang@intel.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Tue, Oct 25, 2022 at 4:18 PM Chao Peng wrote: > > From: "Kirill A. Shutemov" > > Introduce 'memfd_restricted' system call with the ability to create > memory areas that are restricted from userspace access through ordinary > MMU operations (e.g. read/write/mmap). The memory content is expected to > be used through a new in-kernel interface by a third kernel module. > > memfd_restricted() is useful for scenarios where a file descriptor(fd) > can be used as an interface into mm but want to restrict userspace's > ability on the fd. Initially it is designed to provide protections for > KVM encrypted guest memory. > > Normally KVM uses memfd memory via mmapping the memfd into KVM userspace > (e.g. QEMU) and then using the mmaped virtual address to setup the > mapping in the KVM secondary page table (e.g. EPT). With confidential > computing technologies like Intel TDX, the memfd memory may be encrypted > with special key for special software domain (e.g. KVM guest) and is not > expected to be directly accessed by userspace. Precisely, userspace > access to such encrypted memory may lead to host crash so should be > prevented. > > memfd_restricted() provides semantics required for KVM guest encrypted > memory support that a fd created with memfd_restricted() is going to be > used as the source of guest memory in confidential computing environment > and KVM can directly interact with core-mm without the need to expose > the memoy content into KVM userspace. > > KVM userspace is still in charge of the lifecycle of the fd. It should > pass the created fd to KVM. KVM uses the new restrictedmem_get_page() to > obtain the physical memory page and then uses it to populate the KVM > secondary page table entries. > > The userspace restricted memfd can be fallocate-ed or hole-punched > from userspace. When these operations happen, KVM can get notified > through restrictedmem_notifier, it then gets chance to remove any > mapped entries of the range in the secondary page tables. > > memfd_restricted() itself is implemented as a shim layer on top of real > memory file systems (currently tmpfs). Pages in restrictedmem are marked > as unmovable and unevictable, this is required for current confidential > usage. But in future this might be changed. > > By default memfd_restricted() prevents userspace read, write and mmap. > By defining new bit in the 'flags', it can be extended to support other > restricted semantics in the future. > > The system call is currently wired up for x86 arch. > > Signed-off-by: Kirill A. Shutemov > Signed-off-by: Chao Peng > --- Reviewed-by: Fuad Tabba And I'm working on porting to arm64 and testing V9. Cheers, /fuad > arch/x86/entry/syscalls/syscall_32.tbl | 1 + > arch/x86/entry/syscalls/syscall_64.tbl | 1 + > include/linux/restrictedmem.h | 62 ++++++ > include/linux/syscalls.h | 1 + > include/uapi/asm-generic/unistd.h | 5 +- > include/uapi/linux/magic.h | 1 + > kernel/sys_ni.c | 3 + > mm/Kconfig | 4 + > mm/Makefile | 1 + > mm/restrictedmem.c | 250 +++++++++++++++++++++++++ > 10 files changed, 328 insertions(+), 1 deletion(-) > create mode 100644 include/linux/restrictedmem.h > create mode 100644 mm/restrictedmem.c > > diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl > index 320480a8db4f..dc70ba90247e 100644 > --- a/arch/x86/entry/syscalls/syscall_32.tbl > +++ b/arch/x86/entry/syscalls/syscall_32.tbl > @@ -455,3 +455,4 @@ > 448 i386 process_mrelease sys_process_mrelease > 449 i386 futex_waitv sys_futex_waitv > 450 i386 set_mempolicy_home_node sys_set_mempolicy_home_node > +451 i386 memfd_restricted sys_memfd_restricted > diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl > index c84d12608cd2..06516abc8318 100644 > --- a/arch/x86/entry/syscalls/syscall_64.tbl > +++ b/arch/x86/entry/syscalls/syscall_64.tbl > @@ -372,6 +372,7 @@ > 448 common process_mrelease sys_process_mrelease > 449 common futex_waitv sys_futex_waitv > 450 common set_mempolicy_home_node sys_set_mempolicy_home_node > +451 common memfd_restricted sys_memfd_restricted > > # > # Due to a historical design error, certain syscalls are numbered differently > diff --git a/include/linux/restrictedmem.h b/include/linux/restrictedmem.h > new file mode 100644 > index 000000000000..9c37c3ea3180 > --- /dev/null > +++ b/include/linux/restrictedmem.h > @@ -0,0 +1,62 @@ > +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ > +#ifndef _LINUX_RESTRICTEDMEM_H > + > +#include > +#include > +#include > + > +struct restrictedmem_notifier; > + > +struct restrictedmem_notifier_ops { > + void (*invalidate_start)(struct restrictedmem_notifier *notifier, > + pgoff_t start, pgoff_t end); > + void (*invalidate_end)(struct restrictedmem_notifier *notifier, > + pgoff_t start, pgoff_t end); > +}; > + > +struct restrictedmem_notifier { > + struct list_head list; > + const struct restrictedmem_notifier_ops *ops; > +}; > + > +#ifdef CONFIG_RESTRICTEDMEM > + > +void restrictedmem_register_notifier(struct file *file, > + struct restrictedmem_notifier *notifier); > +void restrictedmem_unregister_notifier(struct file *file, > + struct restrictedmem_notifier *notifier); > + > +int restrictedmem_get_page(struct file *file, pgoff_t offset, > + struct page **pagep, int *order); > + > +static inline bool file_is_restrictedmem(struct file *file) > +{ > + return file->f_inode->i_sb->s_magic == RESTRICTEDMEM_MAGIC; > +} > + > +#else > + > +static inline void restrictedmem_register_notifier(struct file *file, > + struct restrictedmem_notifier *notifier) > +{ > +} > + > +static inline void restrictedmem_unregister_notifier(struct file *file, > + struct restrictedmem_notifier *notifier) > +{ > +} > + > +static inline int restrictedmem_get_page(struct file *file, pgoff_t offset, > + struct page **pagep, int *order) > +{ > + return -1; > +} > + > +static inline bool file_is_restrictedmem(struct file *file) > +{ > + return false; > +} > + > +#endif /* CONFIG_RESTRICTEDMEM */ > + > +#endif /* _LINUX_RESTRICTEDMEM_H */ > diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h > index a34b0f9a9972..f9e9e0c820c5 100644 > --- a/include/linux/syscalls.h > +++ b/include/linux/syscalls.h > @@ -1056,6 +1056,7 @@ asmlinkage long sys_memfd_secret(unsigned int flags); > asmlinkage long sys_set_mempolicy_home_node(unsigned long start, unsigned long len, > unsigned long home_node, > unsigned long flags); > +asmlinkage long sys_memfd_restricted(unsigned int flags); > > /* > * Architecture-specific system calls > diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h > index 45fa180cc56a..e93cd35e46d0 100644 > --- a/include/uapi/asm-generic/unistd.h > +++ b/include/uapi/asm-generic/unistd.h > @@ -886,8 +886,11 @@ __SYSCALL(__NR_futex_waitv, sys_futex_waitv) > #define __NR_set_mempolicy_home_node 450 > __SYSCALL(__NR_set_mempolicy_home_node, sys_set_mempolicy_home_node) > > +#define __NR_memfd_restricted 451 > +__SYSCALL(__NR_memfd_restricted, sys_memfd_restricted) > + > #undef __NR_syscalls > -#define __NR_syscalls 451 > +#define __NR_syscalls 452 > > /* > * 32 bit systems traditionally used different > diff --git a/include/uapi/linux/magic.h b/include/uapi/linux/magic.h > index 6325d1d0e90f..8aa38324b90a 100644 > --- a/include/uapi/linux/magic.h > +++ b/include/uapi/linux/magic.h > @@ -101,5 +101,6 @@ > #define DMA_BUF_MAGIC 0x444d4142 /* "DMAB" */ > #define DEVMEM_MAGIC 0x454d444d /* "DMEM" */ > #define SECRETMEM_MAGIC 0x5345434d /* "SECM" */ > +#define RESTRICTEDMEM_MAGIC 0x5245534d /* "RESM" */ > > #endif /* __LINUX_MAGIC_H__ */ > diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c > index 860b2dcf3ac4..7c4a32cbd2e7 100644 > --- a/kernel/sys_ni.c > +++ b/kernel/sys_ni.c > @@ -360,6 +360,9 @@ COND_SYSCALL(pkey_free); > /* memfd_secret */ > COND_SYSCALL(memfd_secret); > > +/* memfd_restricted */ > +COND_SYSCALL(memfd_restricted); > + > /* > * Architecture specific weak syscall entries. > */ > diff --git a/mm/Kconfig b/mm/Kconfig > index 0331f1461f81..0177d53676c7 100644 > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -1076,6 +1076,10 @@ config IO_MAPPING > config SECRETMEM > def_bool ARCH_HAS_SET_DIRECT_MAP && !EMBEDDED > > +config RESTRICTEDMEM > + bool > + depends on TMPFS > + > config ANON_VMA_NAME > bool "Anonymous VMA name support" > depends on PROC_FS && ADVISE_SYSCALLS && MMU > diff --git a/mm/Makefile b/mm/Makefile > index 9a564f836403..6cb6403ffd40 100644 > --- a/mm/Makefile > +++ b/mm/Makefile > @@ -117,6 +117,7 @@ obj-$(CONFIG_PAGE_EXTENSION) += page_ext.o > obj-$(CONFIG_PAGE_TABLE_CHECK) += page_table_check.o > obj-$(CONFIG_CMA_DEBUGFS) += cma_debug.o > obj-$(CONFIG_SECRETMEM) += secretmem.o > +obj-$(CONFIG_RESTRICTEDMEM) += restrictedmem.o > obj-$(CONFIG_CMA_SYSFS) += cma_sysfs.o > obj-$(CONFIG_USERFAULTFD) += userfaultfd.o > obj-$(CONFIG_IDLE_PAGE_TRACKING) += page_idle.o > diff --git a/mm/restrictedmem.c b/mm/restrictedmem.c > new file mode 100644 > index 000000000000..e5bf8907e0f8 > --- /dev/null > +++ b/mm/restrictedmem.c > @@ -0,0 +1,250 @@ > +// SPDX-License-Identifier: GPL-2.0 > +#include "linux/sbitmap.h" > +#include > +#include > +#include > +#include > +#include > +#include > +#include > + > +struct restrictedmem_data { > + struct mutex lock; > + struct file *memfd; > + struct list_head notifiers; > +}; > + > +static void restrictedmem_notifier_invalidate(struct restrictedmem_data *data, > + pgoff_t start, pgoff_t end, bool notify_start) > +{ > + struct restrictedmem_notifier *notifier; > + > + mutex_lock(&data->lock); > + list_for_each_entry(notifier, &data->notifiers, list) { > + if (notify_start) > + notifier->ops->invalidate_start(notifier, start, end); > + else > + notifier->ops->invalidate_end(notifier, start, end); > + } > + mutex_unlock(&data->lock); > +} > + > +static int restrictedmem_release(struct inode *inode, struct file *file) > +{ > + struct restrictedmem_data *data = inode->i_mapping->private_data; > + > + fput(data->memfd); > + kfree(data); > + return 0; > +} > + > +static long restrictedmem_fallocate(struct file *file, int mode, > + loff_t offset, loff_t len) > +{ > + struct restrictedmem_data *data = file->f_mapping->private_data; > + struct file *memfd = data->memfd; > + int ret; > + > + if (mode & FALLOC_FL_PUNCH_HOLE) { > + if (!PAGE_ALIGNED(offset) || !PAGE_ALIGNED(len)) > + return -EINVAL; > + } > + > + restrictedmem_notifier_invalidate(data, offset, offset + len, true); > + ret = memfd->f_op->fallocate(memfd, mode, offset, len); > + restrictedmem_notifier_invalidate(data, offset, offset + len, false); > + return ret; > +} > + > +static const struct file_operations restrictedmem_fops = { > + .release = restrictedmem_release, > + .fallocate = restrictedmem_fallocate, > +}; > + > +static int restrictedmem_getattr(struct user_namespace *mnt_userns, > + const struct path *path, struct kstat *stat, > + u32 request_mask, unsigned int query_flags) > +{ > + struct inode *inode = d_inode(path->dentry); > + struct restrictedmem_data *data = inode->i_mapping->private_data; > + struct file *memfd = data->memfd; > + > + return memfd->f_inode->i_op->getattr(mnt_userns, path, stat, > + request_mask, query_flags); > +} > + > +static int restrictedmem_setattr(struct user_namespace *mnt_userns, > + struct dentry *dentry, struct iattr *attr) > +{ > + struct inode *inode = d_inode(dentry); > + struct restrictedmem_data *data = inode->i_mapping->private_data; > + struct file *memfd = data->memfd; > + int ret; > + > + if (attr->ia_valid & ATTR_SIZE) { > + if (memfd->f_inode->i_size) > + return -EPERM; > + > + if (!PAGE_ALIGNED(attr->ia_size)) > + return -EINVAL; > + } > + > + ret = memfd->f_inode->i_op->setattr(mnt_userns, > + file_dentry(memfd), attr); > + return ret; > +} > + > +static const struct inode_operations restrictedmem_iops = { > + .getattr = restrictedmem_getattr, > + .setattr = restrictedmem_setattr, > +}; > + > +static int restrictedmem_init_fs_context(struct fs_context *fc) > +{ > + if (!init_pseudo(fc, RESTRICTEDMEM_MAGIC)) > + return -ENOMEM; > + > + fc->s_iflags |= SB_I_NOEXEC; > + return 0; > +} > + > +static struct file_system_type restrictedmem_fs = { > + .owner = THIS_MODULE, > + .name = "memfd:restrictedmem", > + .init_fs_context = restrictedmem_init_fs_context, > + .kill_sb = kill_anon_super, > +}; > + > +static struct vfsmount *restrictedmem_mnt; > + > +static __init int restrictedmem_init(void) > +{ > + restrictedmem_mnt = kern_mount(&restrictedmem_fs); > + if (IS_ERR(restrictedmem_mnt)) > + return PTR_ERR(restrictedmem_mnt); > + return 0; > +} > +fs_initcall(restrictedmem_init); > + > +static struct file *restrictedmem_file_create(struct file *memfd) > +{ > + struct restrictedmem_data *data; > + struct address_space *mapping; > + struct inode *inode; > + struct file *file; > + > + data = kzalloc(sizeof(*data), GFP_KERNEL); > + if (!data) > + return ERR_PTR(-ENOMEM); > + > + data->memfd = memfd; > + mutex_init(&data->lock); > + INIT_LIST_HEAD(&data->notifiers); > + > + inode = alloc_anon_inode(restrictedmem_mnt->mnt_sb); > + if (IS_ERR(inode)) { > + kfree(data); > + return ERR_CAST(inode); > + } > + > + inode->i_mode |= S_IFREG; > + inode->i_op = &restrictedmem_iops; > + inode->i_mapping->private_data = data; > + > + file = alloc_file_pseudo(inode, restrictedmem_mnt, > + "restrictedmem", O_RDWR, > + &restrictedmem_fops); > + if (IS_ERR(file)) { > + iput(inode); > + kfree(data); > + return ERR_CAST(file); > + } > + > + file->f_flags |= O_LARGEFILE; > + > + mapping = memfd->f_mapping; > + mapping_set_unevictable(mapping); > + mapping_set_gfp_mask(mapping, > + mapping_gfp_mask(mapping) & ~__GFP_MOVABLE); > + > + return file; > +} > + > +SYSCALL_DEFINE1(memfd_restricted, unsigned int, flags) > +{ > + struct file *file, *restricted_file; > + int fd, err; > + > + if (flags) > + return -EINVAL; > + > + fd = get_unused_fd_flags(0); > + if (fd < 0) > + return fd; > + > + file = shmem_file_setup("memfd:restrictedmem", 0, VM_NORESERVE); > + if (IS_ERR(file)) { > + err = PTR_ERR(file); > + goto err_fd; > + } > + file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE; > + file->f_flags |= O_LARGEFILE; > + > + restricted_file = restrictedmem_file_create(file); > + if (IS_ERR(restricted_file)) { > + err = PTR_ERR(restricted_file); > + fput(file); > + goto err_fd; > + } > + > + fd_install(fd, restricted_file); > + return fd; > +err_fd: > + put_unused_fd(fd); > + return err; > +} > + > +void restrictedmem_register_notifier(struct file *file, > + struct restrictedmem_notifier *notifier) > +{ > + struct restrictedmem_data *data = file->f_mapping->private_data; > + > + mutex_lock(&data->lock); > + list_add(¬ifier->list, &data->notifiers); > + mutex_unlock(&data->lock); > +} > +EXPORT_SYMBOL_GPL(restrictedmem_register_notifier); > + > +void restrictedmem_unregister_notifier(struct file *file, > + struct restrictedmem_notifier *notifier) > +{ > + struct restrictedmem_data *data = file->f_mapping->private_data; > + > + mutex_lock(&data->lock); > + list_del(¬ifier->list); > + mutex_unlock(&data->lock); > +} > +EXPORT_SYMBOL_GPL(restrictedmem_unregister_notifier); > + > +int restrictedmem_get_page(struct file *file, pgoff_t offset, > + struct page **pagep, int *order) > +{ > + struct restrictedmem_data *data = file->f_mapping->private_data; > + struct file *memfd = data->memfd; > + struct page *page; > + int ret; > + > + ret = shmem_getpage(file_inode(memfd), offset, &page, SGP_WRITE); > + if (ret) > + return ret; > + > + *pagep = page; > + if (order) > + *order = thp_order(compound_head(page)); > + > + SetPageUptodate(page); > + unlock_page(page); > + > + return 0; > +} > +EXPORT_SYMBOL_GPL(restrictedmem_get_page); > -- > 2.25.1 >