Loading...
1/*
2 * memfd_create system call and file sealing support
3 *
4 * Code was originally included in shmem.c, and broken out to facilitate
5 * use by hugetlbfs as well as tmpfs.
6 *
7 * This file is released under the GPL.
8 */
9
10#include <linux/fs.h>
11#include <linux/vfs.h>
12#include <linux/pagemap.h>
13#include <linux/file.h>
14#include <linux/mm.h>
15#include <linux/sched/signal.h>
16#include <linux/khugepaged.h>
17#include <linux/syscalls.h>
18#include <linux/hugetlb.h>
19#include <linux/shmem_fs.h>
20#include <linux/memfd.h>
21#include <linux/pid_namespace.h>
22#include <uapi/linux/memfd.h>
23
24/*
25 * We need a tag: a new tag would expand every xa_node by 8 bytes,
26 * so reuse a tag which we firmly believe is never set or cleared on tmpfs
27 * or hugetlbfs because they are memory only filesystems.
28 */
29#define MEMFD_TAG_PINNED PAGECACHE_TAG_TOWRITE
30#define LAST_SCAN 4 /* about 150ms max */
31
32static bool memfd_folio_has_extra_refs(struct folio *folio)
33{
34 return folio_ref_count(folio) - folio_mapcount(folio) !=
35 folio_nr_pages(folio);
36}
37
38static void memfd_tag_pins(struct xa_state *xas)
39{
40 struct folio *folio;
41 int latency = 0;
42
43 lru_add_drain();
44
45 xas_lock_irq(xas);
46 xas_for_each(xas, folio, ULONG_MAX) {
47 if (!xa_is_value(folio) && memfd_folio_has_extra_refs(folio))
48 xas_set_mark(xas, MEMFD_TAG_PINNED);
49
50 if (++latency < XA_CHECK_SCHED)
51 continue;
52 latency = 0;
53
54 xas_pause(xas);
55 xas_unlock_irq(xas);
56 cond_resched();
57 xas_lock_irq(xas);
58 }
59 xas_unlock_irq(xas);
60}
61
62/*
63 * This is a helper function used by memfd_pin_user_pages() in GUP (gup.c).
64 * It is mainly called to allocate a folio in a memfd when the caller
65 * (memfd_pin_folios()) cannot find a folio in the page cache at a given
66 * index in the mapping.
67 */
68struct folio *memfd_alloc_folio(struct file *memfd, pgoff_t idx)
69{
70#ifdef CONFIG_HUGETLB_PAGE
71 struct folio *folio;
72 gfp_t gfp_mask;
73 int err;
74
75 if (is_file_hugepages(memfd)) {
76 /*
77 * The folio would most likely be accessed by a DMA driver,
78 * therefore, we have zone memory constraints where we can
79 * alloc from. Also, the folio will be pinned for an indefinite
80 * amount of time, so it is not expected to be migrated away.
81 */
82 struct hstate *h = hstate_file(memfd);
83
84 gfp_mask = htlb_alloc_mask(h);
85 gfp_mask &= ~(__GFP_HIGHMEM | __GFP_MOVABLE);
86 idx >>= huge_page_order(h);
87
88 folio = alloc_hugetlb_folio_reserve(h,
89 numa_node_id(),
90 NULL,
91 gfp_mask);
92 if (folio) {
93 err = hugetlb_add_to_page_cache(folio,
94 memfd->f_mapping,
95 idx);
96 if (err) {
97 folio_put(folio);
98 return ERR_PTR(err);
99 }
100 folio_unlock(folio);
101 return folio;
102 }
103 return ERR_PTR(-ENOMEM);
104 }
105#endif
106 return shmem_read_folio(memfd->f_mapping, idx);
107}
108
109/*
110 * Setting SEAL_WRITE requires us to verify there's no pending writer. However,
111 * via get_user_pages(), drivers might have some pending I/O without any active
112 * user-space mappings (eg., direct-IO, AIO). Therefore, we look at all folios
113 * and see whether it has an elevated ref-count. If so, we tag them and wait for
114 * them to be dropped.
115 * The caller must guarantee that no new user will acquire writable references
116 * to those folios to avoid races.
117 */
118static int memfd_wait_for_pins(struct address_space *mapping)
119{
120 XA_STATE(xas, &mapping->i_pages, 0);
121 struct folio *folio;
122 int error, scan;
123
124 memfd_tag_pins(&xas);
125
126 error = 0;
127 for (scan = 0; scan <= LAST_SCAN; scan++) {
128 int latency = 0;
129
130 if (!xas_marked(&xas, MEMFD_TAG_PINNED))
131 break;
132
133 if (!scan)
134 lru_add_drain_all();
135 else if (schedule_timeout_killable((HZ << scan) / 200))
136 scan = LAST_SCAN;
137
138 xas_set(&xas, 0);
139 xas_lock_irq(&xas);
140 xas_for_each_marked(&xas, folio, ULONG_MAX, MEMFD_TAG_PINNED) {
141 bool clear = true;
142
143 if (!xa_is_value(folio) &&
144 memfd_folio_has_extra_refs(folio)) {
145 /*
146 * On the last scan, we clean up all those tags
147 * we inserted; but make a note that we still
148 * found folios pinned.
149 */
150 if (scan == LAST_SCAN)
151 error = -EBUSY;
152 else
153 clear = false;
154 }
155 if (clear)
156 xas_clear_mark(&xas, MEMFD_TAG_PINNED);
157
158 if (++latency < XA_CHECK_SCHED)
159 continue;
160 latency = 0;
161
162 xas_pause(&xas);
163 xas_unlock_irq(&xas);
164 cond_resched();
165 xas_lock_irq(&xas);
166 }
167 xas_unlock_irq(&xas);
168 }
169
170 return error;
171}
172
173unsigned int *memfd_file_seals_ptr(struct file *file)
174{
175 if (shmem_file(file))
176 return &SHMEM_I(file_inode(file))->seals;
177
178#ifdef CONFIG_HUGETLBFS
179 if (is_file_hugepages(file))
180 return &HUGETLBFS_I(file_inode(file))->seals;
181#endif
182
183 return NULL;
184}
185
186#define F_ALL_SEALS (F_SEAL_SEAL | \
187 F_SEAL_EXEC | \
188 F_SEAL_SHRINK | \
189 F_SEAL_GROW | \
190 F_SEAL_WRITE | \
191 F_SEAL_FUTURE_WRITE)
192
193static int memfd_add_seals(struct file *file, unsigned int seals)
194{
195 struct inode *inode = file_inode(file);
196 unsigned int *file_seals;
197 int error;
198
199 /*
200 * SEALING
201 * Sealing allows multiple parties to share a tmpfs or hugetlbfs file
202 * but restrict access to a specific subset of file operations. Seals
203 * can only be added, but never removed. This way, mutually untrusted
204 * parties can share common memory regions with a well-defined policy.
205 * A malicious peer can thus never perform unwanted operations on a
206 * shared object.
207 *
208 * Seals are only supported on special tmpfs or hugetlbfs files and
209 * always affect the whole underlying inode. Once a seal is set, it
210 * may prevent some kinds of access to the file. Currently, the
211 * following seals are defined:
212 * SEAL_SEAL: Prevent further seals from being set on this file
213 * SEAL_SHRINK: Prevent the file from shrinking
214 * SEAL_GROW: Prevent the file from growing
215 * SEAL_WRITE: Prevent write access to the file
216 * SEAL_EXEC: Prevent modification of the exec bits in the file mode
217 *
218 * As we don't require any trust relationship between two parties, we
219 * must prevent seals from being removed. Therefore, sealing a file
220 * only adds a given set of seals to the file, it never touches
221 * existing seals. Furthermore, the "setting seals"-operation can be
222 * sealed itself, which basically prevents any further seal from being
223 * added.
224 *
225 * Semantics of sealing are only defined on volatile files. Only
226 * anonymous tmpfs and hugetlbfs files support sealing. More
227 * importantly, seals are never written to disk. Therefore, there's
228 * no plan to support it on other file types.
229 */
230
231 if (!(file->f_mode & FMODE_WRITE))
232 return -EPERM;
233 if (seals & ~(unsigned int)F_ALL_SEALS)
234 return -EINVAL;
235
236 inode_lock(inode);
237
238 file_seals = memfd_file_seals_ptr(file);
239 if (!file_seals) {
240 error = -EINVAL;
241 goto unlock;
242 }
243
244 if (*file_seals & F_SEAL_SEAL) {
245 error = -EPERM;
246 goto unlock;
247 }
248
249 if ((seals & F_SEAL_WRITE) && !(*file_seals & F_SEAL_WRITE)) {
250 error = mapping_deny_writable(file->f_mapping);
251 if (error)
252 goto unlock;
253
254 error = memfd_wait_for_pins(file->f_mapping);
255 if (error) {
256 mapping_allow_writable(file->f_mapping);
257 goto unlock;
258 }
259 }
260
261 /*
262 * SEAL_EXEC implys SEAL_WRITE, making W^X from the start.
263 */
264 if (seals & F_SEAL_EXEC && inode->i_mode & 0111)
265 seals |= F_SEAL_SHRINK|F_SEAL_GROW|F_SEAL_WRITE|F_SEAL_FUTURE_WRITE;
266
267 *file_seals |= seals;
268 error = 0;
269
270unlock:
271 inode_unlock(inode);
272 return error;
273}
274
275static int memfd_get_seals(struct file *file)
276{
277 unsigned int *seals = memfd_file_seals_ptr(file);
278
279 return seals ? *seals : -EINVAL;
280}
281
282long memfd_fcntl(struct file *file, unsigned int cmd, unsigned int arg)
283{
284 long error;
285
286 switch (cmd) {
287 case F_ADD_SEALS:
288 error = memfd_add_seals(file, arg);
289 break;
290 case F_GET_SEALS:
291 error = memfd_get_seals(file);
292 break;
293 default:
294 error = -EINVAL;
295 break;
296 }
297
298 return error;
299}
300
301#define MFD_NAME_PREFIX "memfd:"
302#define MFD_NAME_PREFIX_LEN (sizeof(MFD_NAME_PREFIX) - 1)
303#define MFD_NAME_MAX_LEN (NAME_MAX - MFD_NAME_PREFIX_LEN)
304
305#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB | MFD_NOEXEC_SEAL | MFD_EXEC)
306
307static int check_sysctl_memfd_noexec(unsigned int *flags)
308{
309#ifdef CONFIG_SYSCTL
310 struct pid_namespace *ns = task_active_pid_ns(current);
311 int sysctl = pidns_memfd_noexec_scope(ns);
312
313 if (!(*flags & (MFD_EXEC | MFD_NOEXEC_SEAL))) {
314 if (sysctl >= MEMFD_NOEXEC_SCOPE_NOEXEC_SEAL)
315 *flags |= MFD_NOEXEC_SEAL;
316 else
317 *flags |= MFD_EXEC;
318 }
319
320 if (!(*flags & MFD_NOEXEC_SEAL) && sysctl >= MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED) {
321 pr_err_ratelimited(
322 "%s[%d]: memfd_create() requires MFD_NOEXEC_SEAL with vm.memfd_noexec=%d\n",
323 current->comm, task_pid_nr(current), sysctl);
324 return -EACCES;
325 }
326#endif
327 return 0;
328}
329
330SYSCALL_DEFINE2(memfd_create,
331 const char __user *, uname,
332 unsigned int, flags)
333{
334 unsigned int *file_seals;
335 struct file *file;
336 int fd, error;
337 char *name;
338 long len;
339
340 if (!(flags & MFD_HUGETLB)) {
341 if (flags & ~(unsigned int)MFD_ALL_FLAGS)
342 return -EINVAL;
343 } else {
344 /* Allow huge page size encoding in flags. */
345 if (flags & ~(unsigned int)(MFD_ALL_FLAGS |
346 (MFD_HUGE_MASK << MFD_HUGE_SHIFT)))
347 return -EINVAL;
348 }
349
350 /* Invalid if both EXEC and NOEXEC_SEAL are set.*/
351 if ((flags & MFD_EXEC) && (flags & MFD_NOEXEC_SEAL))
352 return -EINVAL;
353
354 error = check_sysctl_memfd_noexec(&flags);
355 if (error < 0)
356 return error;
357
358 /* length includes terminating zero */
359 len = strnlen_user(uname, MFD_NAME_MAX_LEN + 1);
360 if (len <= 0)
361 return -EFAULT;
362 if (len > MFD_NAME_MAX_LEN + 1)
363 return -EINVAL;
364
365 name = kmalloc(len + MFD_NAME_PREFIX_LEN, GFP_KERNEL);
366 if (!name)
367 return -ENOMEM;
368
369 strcpy(name, MFD_NAME_PREFIX);
370 if (copy_from_user(&name[MFD_NAME_PREFIX_LEN], uname, len)) {
371 error = -EFAULT;
372 goto err_name;
373 }
374
375 /* terminating-zero may have changed after strnlen_user() returned */
376 if (name[len + MFD_NAME_PREFIX_LEN - 1]) {
377 error = -EFAULT;
378 goto err_name;
379 }
380
381 fd = get_unused_fd_flags((flags & MFD_CLOEXEC) ? O_CLOEXEC : 0);
382 if (fd < 0) {
383 error = fd;
384 goto err_name;
385 }
386
387 if (flags & MFD_HUGETLB) {
388 file = hugetlb_file_setup(name, 0, VM_NORESERVE,
389 HUGETLB_ANONHUGE_INODE,
390 (flags >> MFD_HUGE_SHIFT) &
391 MFD_HUGE_MASK);
392 } else
393 file = shmem_file_setup(name, 0, VM_NORESERVE);
394 if (IS_ERR(file)) {
395 error = PTR_ERR(file);
396 goto err_fd;
397 }
398 file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
399 file->f_flags |= O_LARGEFILE;
400
401 if (flags & MFD_NOEXEC_SEAL) {
402 struct inode *inode = file_inode(file);
403
404 inode->i_mode &= ~0111;
405 file_seals = memfd_file_seals_ptr(file);
406 if (file_seals) {
407 *file_seals &= ~F_SEAL_SEAL;
408 *file_seals |= F_SEAL_EXEC;
409 }
410 } else if (flags & MFD_ALLOW_SEALING) {
411 /* MFD_EXEC and MFD_ALLOW_SEALING are set */
412 file_seals = memfd_file_seals_ptr(file);
413 if (file_seals)
414 *file_seals &= ~F_SEAL_SEAL;
415 }
416
417 fd_install(fd, file);
418 kfree(name);
419 return fd;
420
421err_fd:
422 put_unused_fd(fd);
423err_name:
424 kfree(name);
425 return error;
426}
1/*
2 * memfd_create system call and file sealing support
3 *
4 * Code was originally included in shmem.c, and broken out to facilitate
5 * use by hugetlbfs as well as tmpfs.
6 *
7 * This file is released under the GPL.
8 */
9
10#include <linux/fs.h>
11#include <linux/vfs.h>
12#include <linux/pagemap.h>
13#include <linux/file.h>
14#include <linux/mm.h>
15#include <linux/sched/signal.h>
16#include <linux/khugepaged.h>
17#include <linux/syscalls.h>
18#include <linux/hugetlb.h>
19#include <linux/shmem_fs.h>
20#include <linux/memfd.h>
21#include <linux/pid_namespace.h>
22#include <uapi/linux/memfd.h>
23
24/*
25 * We need a tag: a new tag would expand every xa_node by 8 bytes,
26 * so reuse a tag which we firmly believe is never set or cleared on tmpfs
27 * or hugetlbfs because they are memory only filesystems.
28 */
29#define MEMFD_TAG_PINNED PAGECACHE_TAG_TOWRITE
30#define LAST_SCAN 4 /* about 150ms max */
31
32static bool memfd_folio_has_extra_refs(struct folio *folio)
33{
34 return folio_ref_count(folio) - folio_mapcount(folio) !=
35 folio_nr_pages(folio);
36}
37
38static void memfd_tag_pins(struct xa_state *xas)
39{
40 struct folio *folio;
41 int latency = 0;
42
43 lru_add_drain();
44
45 xas_lock_irq(xas);
46 xas_for_each(xas, folio, ULONG_MAX) {
47 if (!xa_is_value(folio) && memfd_folio_has_extra_refs(folio))
48 xas_set_mark(xas, MEMFD_TAG_PINNED);
49
50 if (++latency < XA_CHECK_SCHED)
51 continue;
52 latency = 0;
53
54 xas_pause(xas);
55 xas_unlock_irq(xas);
56 cond_resched();
57 xas_lock_irq(xas);
58 }
59 xas_unlock_irq(xas);
60}
61
62/*
63 * Setting SEAL_WRITE requires us to verify there's no pending writer. However,
64 * via get_user_pages(), drivers might have some pending I/O without any active
65 * user-space mappings (eg., direct-IO, AIO). Therefore, we look at all folios
66 * and see whether it has an elevated ref-count. If so, we tag them and wait for
67 * them to be dropped.
68 * The caller must guarantee that no new user will acquire writable references
69 * to those folios to avoid races.
70 */
71static int memfd_wait_for_pins(struct address_space *mapping)
72{
73 XA_STATE(xas, &mapping->i_pages, 0);
74 struct folio *folio;
75 int error, scan;
76
77 memfd_tag_pins(&xas);
78
79 error = 0;
80 for (scan = 0; scan <= LAST_SCAN; scan++) {
81 int latency = 0;
82
83 if (!xas_marked(&xas, MEMFD_TAG_PINNED))
84 break;
85
86 if (!scan)
87 lru_add_drain_all();
88 else if (schedule_timeout_killable((HZ << scan) / 200))
89 scan = LAST_SCAN;
90
91 xas_set(&xas, 0);
92 xas_lock_irq(&xas);
93 xas_for_each_marked(&xas, folio, ULONG_MAX, MEMFD_TAG_PINNED) {
94 bool clear = true;
95
96 if (!xa_is_value(folio) &&
97 memfd_folio_has_extra_refs(folio)) {
98 /*
99 * On the last scan, we clean up all those tags
100 * we inserted; but make a note that we still
101 * found folios pinned.
102 */
103 if (scan == LAST_SCAN)
104 error = -EBUSY;
105 else
106 clear = false;
107 }
108 if (clear)
109 xas_clear_mark(&xas, MEMFD_TAG_PINNED);
110
111 if (++latency < XA_CHECK_SCHED)
112 continue;
113 latency = 0;
114
115 xas_pause(&xas);
116 xas_unlock_irq(&xas);
117 cond_resched();
118 xas_lock_irq(&xas);
119 }
120 xas_unlock_irq(&xas);
121 }
122
123 return error;
124}
125
126static unsigned int *memfd_file_seals_ptr(struct file *file)
127{
128 if (shmem_file(file))
129 return &SHMEM_I(file_inode(file))->seals;
130
131#ifdef CONFIG_HUGETLBFS
132 if (is_file_hugepages(file))
133 return &HUGETLBFS_I(file_inode(file))->seals;
134#endif
135
136 return NULL;
137}
138
139#define F_ALL_SEALS (F_SEAL_SEAL | \
140 F_SEAL_EXEC | \
141 F_SEAL_SHRINK | \
142 F_SEAL_GROW | \
143 F_SEAL_WRITE | \
144 F_SEAL_FUTURE_WRITE)
145
146static int memfd_add_seals(struct file *file, unsigned int seals)
147{
148 struct inode *inode = file_inode(file);
149 unsigned int *file_seals;
150 int error;
151
152 /*
153 * SEALING
154 * Sealing allows multiple parties to share a tmpfs or hugetlbfs file
155 * but restrict access to a specific subset of file operations. Seals
156 * can only be added, but never removed. This way, mutually untrusted
157 * parties can share common memory regions with a well-defined policy.
158 * A malicious peer can thus never perform unwanted operations on a
159 * shared object.
160 *
161 * Seals are only supported on special tmpfs or hugetlbfs files and
162 * always affect the whole underlying inode. Once a seal is set, it
163 * may prevent some kinds of access to the file. Currently, the
164 * following seals are defined:
165 * SEAL_SEAL: Prevent further seals from being set on this file
166 * SEAL_SHRINK: Prevent the file from shrinking
167 * SEAL_GROW: Prevent the file from growing
168 * SEAL_WRITE: Prevent write access to the file
169 * SEAL_EXEC: Prevent modification of the exec bits in the file mode
170 *
171 * As we don't require any trust relationship between two parties, we
172 * must prevent seals from being removed. Therefore, sealing a file
173 * only adds a given set of seals to the file, it never touches
174 * existing seals. Furthermore, the "setting seals"-operation can be
175 * sealed itself, which basically prevents any further seal from being
176 * added.
177 *
178 * Semantics of sealing are only defined on volatile files. Only
179 * anonymous tmpfs and hugetlbfs files support sealing. More
180 * importantly, seals are never written to disk. Therefore, there's
181 * no plan to support it on other file types.
182 */
183
184 if (!(file->f_mode & FMODE_WRITE))
185 return -EPERM;
186 if (seals & ~(unsigned int)F_ALL_SEALS)
187 return -EINVAL;
188
189 inode_lock(inode);
190
191 file_seals = memfd_file_seals_ptr(file);
192 if (!file_seals) {
193 error = -EINVAL;
194 goto unlock;
195 }
196
197 if (*file_seals & F_SEAL_SEAL) {
198 error = -EPERM;
199 goto unlock;
200 }
201
202 if ((seals & F_SEAL_WRITE) && !(*file_seals & F_SEAL_WRITE)) {
203 error = mapping_deny_writable(file->f_mapping);
204 if (error)
205 goto unlock;
206
207 error = memfd_wait_for_pins(file->f_mapping);
208 if (error) {
209 mapping_allow_writable(file->f_mapping);
210 goto unlock;
211 }
212 }
213
214 /*
215 * SEAL_EXEC implys SEAL_WRITE, making W^X from the start.
216 */
217 if (seals & F_SEAL_EXEC && inode->i_mode & 0111)
218 seals |= F_SEAL_SHRINK|F_SEAL_GROW|F_SEAL_WRITE|F_SEAL_FUTURE_WRITE;
219
220 *file_seals |= seals;
221 error = 0;
222
223unlock:
224 inode_unlock(inode);
225 return error;
226}
227
228static int memfd_get_seals(struct file *file)
229{
230 unsigned int *seals = memfd_file_seals_ptr(file);
231
232 return seals ? *seals : -EINVAL;
233}
234
235long memfd_fcntl(struct file *file, unsigned int cmd, unsigned int arg)
236{
237 long error;
238
239 switch (cmd) {
240 case F_ADD_SEALS:
241 error = memfd_add_seals(file, arg);
242 break;
243 case F_GET_SEALS:
244 error = memfd_get_seals(file);
245 break;
246 default:
247 error = -EINVAL;
248 break;
249 }
250
251 return error;
252}
253
254#define MFD_NAME_PREFIX "memfd:"
255#define MFD_NAME_PREFIX_LEN (sizeof(MFD_NAME_PREFIX) - 1)
256#define MFD_NAME_MAX_LEN (NAME_MAX - MFD_NAME_PREFIX_LEN)
257
258#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB | MFD_NOEXEC_SEAL | MFD_EXEC)
259
260static int check_sysctl_memfd_noexec(unsigned int *flags)
261{
262#ifdef CONFIG_SYSCTL
263 struct pid_namespace *ns = task_active_pid_ns(current);
264 int sysctl = pidns_memfd_noexec_scope(ns);
265
266 if (!(*flags & (MFD_EXEC | MFD_NOEXEC_SEAL))) {
267 if (sysctl >= MEMFD_NOEXEC_SCOPE_NOEXEC_SEAL)
268 *flags |= MFD_NOEXEC_SEAL;
269 else
270 *flags |= MFD_EXEC;
271 }
272
273 if (!(*flags & MFD_NOEXEC_SEAL) && sysctl >= MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED) {
274 pr_err_ratelimited(
275 "%s[%d]: memfd_create() requires MFD_NOEXEC_SEAL with vm.memfd_noexec=%d\n",
276 current->comm, task_pid_nr(current), sysctl);
277 return -EACCES;
278 }
279#endif
280 return 0;
281}
282
283SYSCALL_DEFINE2(memfd_create,
284 const char __user *, uname,
285 unsigned int, flags)
286{
287 unsigned int *file_seals;
288 struct file *file;
289 int fd, error;
290 char *name;
291 long len;
292
293 if (!(flags & MFD_HUGETLB)) {
294 if (flags & ~(unsigned int)MFD_ALL_FLAGS)
295 return -EINVAL;
296 } else {
297 /* Allow huge page size encoding in flags. */
298 if (flags & ~(unsigned int)(MFD_ALL_FLAGS |
299 (MFD_HUGE_MASK << MFD_HUGE_SHIFT)))
300 return -EINVAL;
301 }
302
303 /* Invalid if both EXEC and NOEXEC_SEAL are set.*/
304 if ((flags & MFD_EXEC) && (flags & MFD_NOEXEC_SEAL))
305 return -EINVAL;
306
307 error = check_sysctl_memfd_noexec(&flags);
308 if (error < 0)
309 return error;
310
311 /* length includes terminating zero */
312 len = strnlen_user(uname, MFD_NAME_MAX_LEN + 1);
313 if (len <= 0)
314 return -EFAULT;
315 if (len > MFD_NAME_MAX_LEN + 1)
316 return -EINVAL;
317
318 name = kmalloc(len + MFD_NAME_PREFIX_LEN, GFP_KERNEL);
319 if (!name)
320 return -ENOMEM;
321
322 strcpy(name, MFD_NAME_PREFIX);
323 if (copy_from_user(&name[MFD_NAME_PREFIX_LEN], uname, len)) {
324 error = -EFAULT;
325 goto err_name;
326 }
327
328 /* terminating-zero may have changed after strnlen_user() returned */
329 if (name[len + MFD_NAME_PREFIX_LEN - 1]) {
330 error = -EFAULT;
331 goto err_name;
332 }
333
334 fd = get_unused_fd_flags((flags & MFD_CLOEXEC) ? O_CLOEXEC : 0);
335 if (fd < 0) {
336 error = fd;
337 goto err_name;
338 }
339
340 if (flags & MFD_HUGETLB) {
341 file = hugetlb_file_setup(name, 0, VM_NORESERVE,
342 HUGETLB_ANONHUGE_INODE,
343 (flags >> MFD_HUGE_SHIFT) &
344 MFD_HUGE_MASK);
345 } else
346 file = shmem_file_setup(name, 0, VM_NORESERVE);
347 if (IS_ERR(file)) {
348 error = PTR_ERR(file);
349 goto err_fd;
350 }
351 file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
352 file->f_flags |= O_LARGEFILE;
353
354 if (flags & MFD_NOEXEC_SEAL) {
355 struct inode *inode = file_inode(file);
356
357 inode->i_mode &= ~0111;
358 file_seals = memfd_file_seals_ptr(file);
359 if (file_seals) {
360 *file_seals &= ~F_SEAL_SEAL;
361 *file_seals |= F_SEAL_EXEC;
362 }
363 } else if (flags & MFD_ALLOW_SEALING) {
364 /* MFD_EXEC and MFD_ALLOW_SEALING are set */
365 file_seals = memfd_file_seals_ptr(file);
366 if (file_seals)
367 *file_seals &= ~F_SEAL_SEAL;
368 }
369
370 fd_install(fd, file);
371 kfree(name);
372 return fd;
373
374err_fd:
375 put_unused_fd(fd);
376err_name:
377 kfree(name);
378 return error;
379}