1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright IBM Corporation, 2021
  4 *
  5 * Author: Mike Rapoport <rppt@linux.ibm.com>
  6 */
  7
  8#include <linux/mm.h>
  9#include <linux/fs.h>
 10#include <linux/swap.h>
 11#include <linux/mount.h>
 12#include <linux/memfd.h>
 13#include <linux/bitops.h>
 14#include <linux/printk.h>
 15#include <linux/pagemap.h>
 16#include <linux/syscalls.h>
 17#include <linux/pseudo_fs.h>
 18#include <linux/secretmem.h>
 19#include <linux/set_memory.h>
 20#include <linux/sched/signal.h>
 21
 22#include <uapi/linux/magic.h>
 23
 24#include <asm/tlbflush.h>
 25
 26#include "internal.h"
 27
 28#undef pr_fmt
 29#define pr_fmt(fmt) "secretmem: " fmt
 30
 31/*
 32 * Define mode and flag masks to allow validation of the system call
 33 * parameters.
 34 */
 35#define SECRETMEM_MODE_MASK	(0x0)
 36#define SECRETMEM_FLAGS_MASK	SECRETMEM_MODE_MASK
 37
 38static bool secretmem_enable __ro_after_init = 1;
 39module_param_named(enable, secretmem_enable, bool, 0400);
 40MODULE_PARM_DESC(secretmem_enable,
 41		 "Enable secretmem and memfd_secret(2) system call");
 42
 43static atomic_t secretmem_users;
 44
 45bool secretmem_active(void)
 46{
 47	return !!atomic_read(&secretmem_users);
 48}
 49
 50static vm_fault_t secretmem_fault(struct vm_fault *vmf)
 51{
 52	struct address_space *mapping = vmf->vma->vm_file->f_mapping;
 53	struct inode *inode = file_inode(vmf->vma->vm_file);
 54	pgoff_t offset = vmf->pgoff;
 55	gfp_t gfp = vmf->gfp_mask;
 56	unsigned long addr;
 57	struct page *page;
 58	struct folio *folio;
 59	vm_fault_t ret;
 60	int err;
 61
 62	if (((loff_t)vmf->pgoff << PAGE_SHIFT) >= i_size_read(inode))
 63		return vmf_error(-EINVAL);
 64
 65	filemap_invalidate_lock_shared(mapping);
 66
 67retry:
 68	page = find_lock_page(mapping, offset);
 69	if (!page) {
 70		folio = folio_alloc(gfp | __GFP_ZERO, 0);
 71		if (!folio) {
 72			ret = VM_FAULT_OOM;
 73			goto out;
 74		}
 75
 76		page = &folio->page;
 77		err = set_direct_map_invalid_noflush(page);
 78		if (err) {
 79			folio_put(folio);
 80			ret = vmf_error(err);
 81			goto out;
 82		}
 83
 84		__folio_mark_uptodate(folio);
 85		err = filemap_add_folio(mapping, folio, offset, gfp);
 86		if (unlikely(err)) {
 87			folio_put(folio);
 88			/*
 89			 * If a split of large page was required, it
 90			 * already happened when we marked the page invalid
 91			 * which guarantees that this call won't fail
 92			 */
 93			set_direct_map_default_noflush(page);
 94			if (err == -EEXIST)
 95				goto retry;
 96
 97			ret = vmf_error(err);
 98			goto out;
 99		}
100
101		addr = (unsigned long)page_address(page);
102		flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
103	}
104
105	vmf->page = page;
106	ret = VM_FAULT_LOCKED;
107
108out:
109	filemap_invalidate_unlock_shared(mapping);
110	return ret;
111}
112
113static const struct vm_operations_struct secretmem_vm_ops = {
114	.fault = secretmem_fault,
115};
116
117static int secretmem_release(struct inode *inode, struct file *file)
118{
119	atomic_dec(&secretmem_users);
120	return 0;
121}
122
123static int secretmem_mmap(struct file *file, struct vm_area_struct *vma)
124{
125	unsigned long len = vma->vm_end - vma->vm_start;
126
127	if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0)
128		return -EINVAL;
129
130	if (!mlock_future_ok(vma->vm_mm, vma->vm_flags | VM_LOCKED, len))
131		return -EAGAIN;
132
133	vm_flags_set(vma, VM_LOCKED | VM_DONTDUMP);
134	vma->vm_ops = &secretmem_vm_ops;
135
136	return 0;
137}
138
139bool vma_is_secretmem(struct vm_area_struct *vma)
140{
141	return vma->vm_ops == &secretmem_vm_ops;
142}
143
144static const struct file_operations secretmem_fops = {
145	.release	= secretmem_release,
146	.mmap		= secretmem_mmap,
147};
148
149static int secretmem_migrate_folio(struct address_space *mapping,
150		struct folio *dst, struct folio *src, enum migrate_mode mode)
151{
152	return -EBUSY;
153}
154
155static void secretmem_free_folio(struct folio *folio)
 
 
156{
157	set_direct_map_default_noflush(&folio->page);
158	folio_zero_segment(folio, 0, folio_size(folio));
159}
160
161const struct address_space_operations secretmem_aops = {
162	.dirty_folio	= noop_dirty_folio,
163	.free_folio	= secretmem_free_folio,
164	.migrate_folio	= secretmem_migrate_folio,
165};
166
167static int secretmem_setattr(struct mnt_idmap *idmap,
168			     struct dentry *dentry, struct iattr *iattr)
169{
170	struct inode *inode = d_inode(dentry);
171	struct address_space *mapping = inode->i_mapping;
172	unsigned int ia_valid = iattr->ia_valid;
173	int ret;
174
175	filemap_invalidate_lock(mapping);
176
177	if ((ia_valid & ATTR_SIZE) && inode->i_size)
178		ret = -EINVAL;
179	else
180		ret = simple_setattr(idmap, dentry, iattr);
181
182	filemap_invalidate_unlock(mapping);
183
184	return ret;
185}
186
187static const struct inode_operations secretmem_iops = {
188	.setattr = secretmem_setattr,
 
 
 
189};
190
191static struct vfsmount *secretmem_mnt;
192
193static struct file *secretmem_file_create(unsigned long flags)
194{
195	struct file *file;
196	struct inode *inode;
197	const char *anon_name = "[secretmem]";
198	const struct qstr qname = QSTR_INIT(anon_name, strlen(anon_name));
199	int err;
200
201	inode = alloc_anon_inode(secretmem_mnt->mnt_sb);
202	if (IS_ERR(inode))
203		return ERR_CAST(inode);
204
205	err = security_inode_init_security_anon(inode, &qname, NULL);
206	if (err) {
207		file = ERR_PTR(err);
208		goto err_free_inode;
209	}
210
211	file = alloc_file_pseudo(inode, secretmem_mnt, "secretmem",
212				 O_RDWR, &secretmem_fops);
213	if (IS_ERR(file))
214		goto err_free_inode;
215
216	mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
217	mapping_set_unevictable(inode->i_mapping);
218
219	inode->i_op = &secretmem_iops;
220	inode->i_mapping->a_ops = &secretmem_aops;
221
222	/* pretend we are a normal file with zero size */
223	inode->i_mode |= S_IFREG;
224	inode->i_size = 0;
225
226	return file;
227
228err_free_inode:
229	iput(inode);
230	return file;
231}
232
233SYSCALL_DEFINE1(memfd_secret, unsigned int, flags)
234{
235	struct file *file;
236	int fd, err;
237
238	/* make sure local flags do not confict with global fcntl.h */
239	BUILD_BUG_ON(SECRETMEM_FLAGS_MASK & O_CLOEXEC);
240
241	if (!secretmem_enable)
242		return -ENOSYS;
243
244	if (flags & ~(SECRETMEM_FLAGS_MASK | O_CLOEXEC))
245		return -EINVAL;
246	if (atomic_read(&secretmem_users) < 0)
247		return -ENFILE;
248
249	fd = get_unused_fd_flags(flags & O_CLOEXEC);
250	if (fd < 0)
251		return fd;
252
253	file = secretmem_file_create(flags);
254	if (IS_ERR(file)) {
255		err = PTR_ERR(file);
256		goto err_put_fd;
257	}
258
259	file->f_flags |= O_LARGEFILE;
260
261	atomic_inc(&secretmem_users);
262	fd_install(fd, file);
 
263	return fd;
264
265err_put_fd:
266	put_unused_fd(fd);
267	return err;
268}
269
270static int secretmem_init_fs_context(struct fs_context *fc)
271{
272	return init_pseudo(fc, SECRETMEM_MAGIC) ? 0 : -ENOMEM;
273}
274
275static struct file_system_type secretmem_fs = {
276	.name		= "secretmem",
277	.init_fs_context = secretmem_init_fs_context,
278	.kill_sb	= kill_anon_super,
279};
280
281static int __init secretmem_init(void)
282{
 
 
283	if (!secretmem_enable)
284		return 0;
285
286	secretmem_mnt = kern_mount(&secretmem_fs);
287	if (IS_ERR(secretmem_mnt))
288		return PTR_ERR(secretmem_mnt);
289
290	/* prevent secretmem mappings from ever getting PROT_EXEC */
291	secretmem_mnt->mnt_flags |= MNT_NOEXEC;
292
293	return 0;
294}
295fs_initcall(secretmem_init);

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright IBM Corporation, 2021
  4 *
  5 * Author: Mike Rapoport <rppt@linux.ibm.com>
  6 */
  7
  8#include <linux/mm.h>
  9#include <linux/fs.h>
 10#include <linux/swap.h>
 11#include <linux/mount.h>
 12#include <linux/memfd.h>
 13#include <linux/bitops.h>
 14#include <linux/printk.h>
 15#include <linux/pagemap.h>
 16#include <linux/syscalls.h>
 17#include <linux/pseudo_fs.h>
 18#include <linux/secretmem.h>
 19#include <linux/set_memory.h>
 20#include <linux/sched/signal.h>
 21
 22#include <uapi/linux/magic.h>
 23
 24#include <asm/tlbflush.h>
 25
 26#include "internal.h"
 27
 28#undef pr_fmt
 29#define pr_fmt(fmt) "secretmem: " fmt
 30
 31/*
 32 * Define mode and flag masks to allow validation of the system call
 33 * parameters.
 34 */
 35#define SECRETMEM_MODE_MASK	(0x0)
 36#define SECRETMEM_FLAGS_MASK	SECRETMEM_MODE_MASK
 37
 38static bool secretmem_enable __ro_after_init;
 39module_param_named(enable, secretmem_enable, bool, 0400);
 40MODULE_PARM_DESC(secretmem_enable,
 41		 "Enable secretmem and memfd_secret(2) system call");
 42
 43static atomic_t secretmem_users;
 44
 45bool secretmem_active(void)
 46{
 47	return !!atomic_read(&secretmem_users);
 48}
 49
 50static vm_fault_t secretmem_fault(struct vm_fault *vmf)
 51{
 52	struct address_space *mapping = vmf->vma->vm_file->f_mapping;
 53	struct inode *inode = file_inode(vmf->vma->vm_file);
 54	pgoff_t offset = vmf->pgoff;
 55	gfp_t gfp = vmf->gfp_mask;
 56	unsigned long addr;
 57	struct page *page;
 
 
 58	int err;
 59
 60	if (((loff_t)vmf->pgoff << PAGE_SHIFT) >= i_size_read(inode))
 61		return vmf_error(-EINVAL);
 62
 
 
 63retry:
 64	page = find_lock_page(mapping, offset);
 65	if (!page) {
 66		page = alloc_page(gfp | __GFP_ZERO);
 67		if (!page)
 68			return VM_FAULT_OOM;
 
 
 69
 
 70		err = set_direct_map_invalid_noflush(page);
 71		if (err) {
 72			put_page(page);
 73			return vmf_error(err);
 
 74		}
 75
 76		__SetPageUptodate(page);
 77		err = add_to_page_cache_lru(page, mapping, offset, gfp);
 78		if (unlikely(err)) {
 79			put_page(page);
 80			/*
 81			 * If a split of large page was required, it
 82			 * already happened when we marked the page invalid
 83			 * which guarantees that this call won't fail
 84			 */
 85			set_direct_map_default_noflush(page);
 86			if (err == -EEXIST)
 87				goto retry;
 88
 89			return vmf_error(err);
 
 90		}
 91
 92		addr = (unsigned long)page_address(page);
 93		flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
 94	}
 95
 96	vmf->page = page;
 97	return VM_FAULT_LOCKED;
 
 
 
 
 98}
 99
100static const struct vm_operations_struct secretmem_vm_ops = {
101	.fault = secretmem_fault,
102};
103
104static int secretmem_release(struct inode *inode, struct file *file)
105{
106	atomic_dec(&secretmem_users);
107	return 0;
108}
109
110static int secretmem_mmap(struct file *file, struct vm_area_struct *vma)
111{
112	unsigned long len = vma->vm_end - vma->vm_start;
113
114	if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0)
115		return -EINVAL;
116
117	if (mlock_future_check(vma->vm_mm, vma->vm_flags | VM_LOCKED, len))
118		return -EAGAIN;
119
120	vma->vm_flags |= VM_LOCKED | VM_DONTDUMP;
121	vma->vm_ops = &secretmem_vm_ops;
122
123	return 0;
124}
125
126bool vma_is_secretmem(struct vm_area_struct *vma)
127{
128	return vma->vm_ops == &secretmem_vm_ops;
129}
130
131static const struct file_operations secretmem_fops = {
132	.release	= secretmem_release,
133	.mmap		= secretmem_mmap,
134};
135
136static bool secretmem_isolate_page(struct page *page, isolate_mode_t mode)
 
137{
138	return false;
139}
140
141static int secretmem_migratepage(struct address_space *mapping,
142				 struct page *newpage, struct page *page,
143				 enum migrate_mode mode)
144{
145	return -EBUSY;
 
146}
147
148static void secretmem_freepage(struct page *page)
 
 
 
 
 
 
 
149{
150	set_direct_map_default_noflush(page);
151	clear_highpage(page);
 
 
 
 
 
 
 
 
 
 
 
 
 
152}
153
154const struct address_space_operations secretmem_aops = {
155	.set_page_dirty	= __set_page_dirty_no_writeback,
156	.freepage	= secretmem_freepage,
157	.migratepage	= secretmem_migratepage,
158	.isolate_page	= secretmem_isolate_page,
159};
160
161static struct vfsmount *secretmem_mnt;
162
163static struct file *secretmem_file_create(unsigned long flags)
164{
165	struct file *file = ERR_PTR(-ENOMEM);
166	struct inode *inode;
 
 
 
167
168	inode = alloc_anon_inode(secretmem_mnt->mnt_sb);
169	if (IS_ERR(inode))
170		return ERR_CAST(inode);
171
 
 
 
 
 
 
172	file = alloc_file_pseudo(inode, secretmem_mnt, "secretmem",
173				 O_RDWR, &secretmem_fops);
174	if (IS_ERR(file))
175		goto err_free_inode;
176
177	mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
178	mapping_set_unevictable(inode->i_mapping);
179
 
180	inode->i_mapping->a_ops = &secretmem_aops;
181
182	/* pretend we are a normal file with zero size */
183	inode->i_mode |= S_IFREG;
184	inode->i_size = 0;
185
186	return file;
187
188err_free_inode:
189	iput(inode);
190	return file;
191}
192
193SYSCALL_DEFINE1(memfd_secret, unsigned int, flags)
194{
195	struct file *file;
196	int fd, err;
197
198	/* make sure local flags do not confict with global fcntl.h */
199	BUILD_BUG_ON(SECRETMEM_FLAGS_MASK & O_CLOEXEC);
200
201	if (!secretmem_enable)
202		return -ENOSYS;
203
204	if (flags & ~(SECRETMEM_FLAGS_MASK | O_CLOEXEC))
205		return -EINVAL;
 
 
206
207	fd = get_unused_fd_flags(flags & O_CLOEXEC);
208	if (fd < 0)
209		return fd;
210
211	file = secretmem_file_create(flags);
212	if (IS_ERR(file)) {
213		err = PTR_ERR(file);
214		goto err_put_fd;
215	}
216
217	file->f_flags |= O_LARGEFILE;
218
 
219	fd_install(fd, file);
220	atomic_inc(&secretmem_users);
221	return fd;
222
223err_put_fd:
224	put_unused_fd(fd);
225	return err;
226}
227
228static int secretmem_init_fs_context(struct fs_context *fc)
229{
230	return init_pseudo(fc, SECRETMEM_MAGIC) ? 0 : -ENOMEM;
231}
232
233static struct file_system_type secretmem_fs = {
234	.name		= "secretmem",
235	.init_fs_context = secretmem_init_fs_context,
236	.kill_sb	= kill_anon_super,
237};
238
239static int secretmem_init(void)
240{
241	int ret = 0;
242
243	if (!secretmem_enable)
244		return ret;
245
246	secretmem_mnt = kern_mount(&secretmem_fs);
247	if (IS_ERR(secretmem_mnt))
248		ret = PTR_ERR(secretmem_mnt);
249
250	/* prevent secretmem mappings from ever getting PROT_EXEC */
251	secretmem_mnt->mnt_flags |= MNT_NOEXEC;
252
253	return ret;
254}
255fs_initcall(secretmem_init);