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 1C8A4C352A1 for ; Tue, 6 Dec 2022 15:04:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234597AbiLFPD7 (ORCPT ); Tue, 6 Dec 2022 10:03:59 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57526 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234603AbiLFPDd (ORCPT ); Tue, 6 Dec 2022 10:03:33 -0500 Received: from mail-lj1-x233.google.com (mail-lj1-x233.google.com [IPv6:2a00:1450:4864:20::233]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 09BCC63A7 for ; Tue, 6 Dec 2022 06:57:43 -0800 (PST) Received: by mail-lj1-x233.google.com with SMTP id f20so4328151lja.4 for ; Tue, 06 Dec 2022 06:57:43 -0800 (PST) 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=0XPbXdU92A3Vbo6jx2Cx531jASa7Ki17T5/Nsb9rRng=; b=XqMSBIgfXZ97PVcBvD1U1HvfJDnv2ulxZ4lUJNkDwdHKji8COqlfTO6ipYkPimEezz iFTEvo+SDi51jVNIqvUww8ZbHZHR6eMlDmrsidSu74ph8aNEfNWYg1WPjGx4wJeqwNHQ Cch6QEXQS9sNl7vdgTjz2smXr4cV9JOOm8HPtXqHN0rNowD59k5QGHdGFHRAki/8d6De bjY3biz+emJMXqQgCsv5mbV6SceEQJU4KWkMXx69hDktIJDwN0M0RM2OEfMP9bmFETNK kMY5x+/sRwzmk9/yUhiTgVK9VFWwVD76O/i1J9h9ZF0RkkY6PetFKDInF8I8PWheDLwt cr2g== 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=0XPbXdU92A3Vbo6jx2Cx531jASa7Ki17T5/Nsb9rRng=; b=y8NVstQlxpS6NHbY21QPWkgAUoSTv/2msy6swIN67ik9sf2fO4wb5qETPxCw11vHtb b93Nrc0NOwcY/rXvXrVpUoYwfzotSzdXfhD4CY2zCqGRilnjPTYNxqQhTBrtBL7u0/Za 9uIEyxGirdphWcic0gd4mhM9rP5usSQZNkdfCbinBlIPDOoz7c60xcMb1Vq21p9BCQWL uw5j9iC8nzpN15CFcOfOtt+cY8QRaugyCQTZcL/DhX66x9nnq4JX7zCNQ+fyjruC7Wxw FI6J7lWNTEo6ytcOYHgczuptf0AK3jiNE2I1nHH18EPD5O9xTyhcvUUKT94n4HmLwN6Z Lzdg== X-Gm-Message-State: ANoB5pl07OrIH6RInCZLHNBA9flrVRI/yAyUuzsfaLeg3b6g7TmnOvYy MEcnri2FZr0l2QrCB2r2BLzusBsFpgmLzGSwVI2RNQ== X-Google-Smtp-Source: AA0mqf5y0IHxa1cY6lA+S2VRxPAmszz8YG5YXRqVfKmJwXsSnLzKVgXJZSMC2rc0NSzJ88PFVF+vSqyeLihmyTrbbR8= X-Received: by 2002:a2e:bf17:0:b0:277:394:34e with SMTP id c23-20020a2ebf17000000b002770394034emr19956934ljr.18.1670338661326; Tue, 06 Dec 2022 06:57:41 -0800 (PST) MIME-Version: 1.0 References: <20221202061347.1070246-1-chao.p.peng@linux.intel.com> <20221202061347.1070246-2-chao.p.peng@linux.intel.com> In-Reply-To: <20221202061347.1070246-2-chao.p.peng@linux.intel.com> From: Fuad Tabba Date: Tue, 6 Dec 2022 14:57:04 +0000 Message-ID: Subject: Re: [PATCH v10 1/9] 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 , Arnd Bergmann , Naoya Horiguchi , Miaohe Lin , 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, wei.w.wang@intel.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org Hi, On Fri, Dec 2, 2022 at 6:18 AM 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 the 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. nit: memory > > 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 hole-punched, KVM can get notified through > invalidate_start/invalidate_end() callbacks, KVM then gets chance to > remove any mapped entries of the range in the secondary page tables. > > Machine check can happen for memory pages in the restricted memfd, > instead of routing this directly to userspace, we call the error() > callback that KVM registered. KVM then gets chance to handle it > correctly. > > 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. Reviewed-by: Fuad Tabba After wiring the system call for arm64 (on qemu/arm64): Tested-by: Fuad Tabba Cheers, /fuad > > Signed-off-by: Kirill A. Shutemov > Signed-off-by: Chao Peng > --- > arch/x86/entry/syscalls/syscall_32.tbl | 1 + > arch/x86/entry/syscalls/syscall_64.tbl | 1 + > include/linux/restrictedmem.h | 71 ++++++ > 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/memory-failure.c | 3 + > mm/restrictedmem.c | 318 +++++++++++++++++++++++++ > 11 files changed, 408 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..c2700c5daa43 > --- /dev/null > +++ b/include/linux/restrictedmem.h > @@ -0,0 +1,71 @@ > +/* 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); > + void (*error)(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; > +} > + > +void restrictedmem_error_page(struct page *page, struct address_space *mapping); > + > +#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; > +} > + > +static inline void restrictedmem_error_page(struct page *page, > + struct address_space *mapping) > +{ > +} > + > +#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 57e1d8c5b505..06b0e1d6b8c1 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 8e105e5b3e29..bcbb0edf9ba1 100644 > --- a/mm/Makefile > +++ b/mm/Makefile > @@ -121,6 +121,7 @@ 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/memory-failure.c b/mm/memory-failure.c > index 145bb561ddb3..f91b444e471e 100644 > --- a/mm/memory-failure.c > +++ b/mm/memory-failure.c > @@ -62,6 +62,7 @@ > #include > #include > #include > +#include > #include "swap.h" > #include "internal.h" > #include "ras/ras_event.h" > @@ -940,6 +941,8 @@ static int me_pagecache_clean(struct page_state *ps, struct page *p) > goto out; > } > > + restrictedmem_error_page(p, mapping); > + > /* > * The shmem page is kept in page cache instead of truncating > * so is expected to have an extra refcount after error-handling. > diff --git a/mm/restrictedmem.c b/mm/restrictedmem.c > new file mode 100644 > index 000000000000..56953c204e5c > --- /dev/null > +++ b/mm/restrictedmem.c > @@ -0,0 +1,318 @@ > +// 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_invalidate_start(struct restrictedmem_data *data, > + pgoff_t start, pgoff_t end) > +{ > + struct restrictedmem_notifier *notifier; > + > + mutex_lock(&data->lock); > + list_for_each_entry(notifier, &data->notifiers, list) { > + notifier->ops->invalidate_start(notifier, start, end); > + } > + mutex_unlock(&data->lock); > +} > + > +static void restrictedmem_invalidate_end(struct restrictedmem_data *data, > + pgoff_t start, pgoff_t end) > +{ > + struct restrictedmem_notifier *notifier; > + > + mutex_lock(&data->lock); > + list_for_each_entry(notifier, &data->notifiers, list) { > + notifier->ops->invalidate_end(notifier, start, end); > + } > + mutex_unlock(&data->lock); > +} > + > +static void restrictedmem_notifier_error(struct restrictedmem_data *data, > + pgoff_t start, pgoff_t end) > +{ > + struct restrictedmem_notifier *notifier; > + > + mutex_lock(&data->lock); > + list_for_each_entry(notifier, &data->notifiers, list) { > + notifier->ops->error(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_punch_hole(struct restrictedmem_data *data, int mode, > + loff_t offset, loff_t len) > +{ > + int ret; > + pgoff_t start, end; > + struct file *memfd = data->memfd; > + > + if (!PAGE_ALIGNED(offset) || !PAGE_ALIGNED(len)) > + return -EINVAL; > + > + start = offset >> PAGE_SHIFT; > + end = (offset + len) >> PAGE_SHIFT; > + > + restrictedmem_invalidate_start(data, start, end); > + ret = memfd->f_op->fallocate(memfd, mode, offset, len); > + restrictedmem_invalidate_end(data, start, end); > + > + return ret; > +} > + > +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; > + > + if (mode & FALLOC_FL_PUNCH_HOLE) > + return restrictedmem_punch_hole(data, mode, offset, len); > + > + return memfd->f_op->fallocate(memfd, mode, offset, len); > +} > + > +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; > + > + /* > + * These pages are currently unmovable so don't place them into movable > + * pageblocks (e.g. CMA and ZONE_MOVABLE). > + */ > + 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 folio *folio; > + struct page *page; > + int ret; > + > + ret = shmem_get_folio(file_inode(memfd), offset, &folio, SGP_WRITE); > + if (ret) > + return ret; > + > + page = folio_file_page(folio, offset); > + *pagep = page; > + if (order) > + *order = thp_order(compound_head(page)); > + > + SetPageUptodate(page); > + unlock_page(page); > + > + return 0; > +} > +EXPORT_SYMBOL_GPL(restrictedmem_get_page); > + > +void restrictedmem_error_page(struct page *page, struct address_space *mapping) > +{ > + struct super_block *sb = restrictedmem_mnt->mnt_sb; > + struct inode *inode, *next; > + > + if (!shmem_mapping(mapping)) > + return; > + > + spin_lock(&sb->s_inode_list_lock); > + list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) { > + struct restrictedmem_data *data = inode->i_mapping->private_data; > + struct file *memfd = data->memfd; > + > + if (memfd->f_mapping == mapping) { > + pgoff_t start, end; > + > + spin_unlock(&sb->s_inode_list_lock); > + > + start = page->index; > + end = start + thp_nr_pages(page); > + restrictedmem_notifier_error(data, start, end); > + return; > + } > + } > + spin_unlock(&sb->s_inode_list_lock); > +} > -- > 2.25.1 >