1 // SPDX-License-Identifier: GPL-2.0-or-later
2 // Copyright (c) 2025 Miklos Szeredi <miklos@szeredi.hu>
3
4 #define _GNU_SOURCE
5 #include <fcntl.h>
6 #include <sched.h>
7 #include <stdio.h>
8 #include <string.h>
9 #include <sys/stat.h>
10 #include <sys/mount.h>
11 #include <linux/fanotify.h>
12 #include <unistd.h>
13 #include <sys/fanotify.h>
14 #include <sys/syscall.h>
15
16 #include "../../kselftest_harness.h"
17 #include "../statmount/statmount.h"
18
19 #ifndef FAN_MNT_ATTACH
20 struct fanotify_event_info_mnt {
21 struct fanotify_event_info_header hdr;
22 __u64 mnt_id;
23 };
24 #define FAN_MNT_ATTACH 0x01000000 /* Mount was attached */
25 #endif
26
27 #ifndef FAN_MNT_DETACH
28 #define FAN_MNT_DETACH 0x02000000 /* Mount was detached */
29 #endif
30
31 #ifndef FAN_REPORT_MNT
32 #define FAN_REPORT_MNT 0x00004000 /* Report mount events */
33 #endif
34
35 #ifndef FAN_MARK_MNTNS
36 #define FAN_MARK_MNTNS 0x00000110
37 #endif
38
get_mnt_id(struct __test_metadata * const _metadata,const char * path)39 static uint64_t get_mnt_id(struct __test_metadata *const _metadata,
40 const char *path)
41 {
42 struct statx sx;
43
44 ASSERT_EQ(statx(AT_FDCWD, path, 0, STATX_MNT_ID_UNIQUE, &sx), 0);
45 ASSERT_TRUE(!!(sx.stx_mask & STATX_MNT_ID_UNIQUE));
46 return sx.stx_mnt_id;
47 }
48
49 static const char root_mntpoint_templ[] = "/tmp/mount-notify_test_root.XXXXXX";
50
51 static const int mark_cmds[] = {
52 FAN_MARK_ADD,
53 FAN_MARK_REMOVE,
54 FAN_MARK_FLUSH
55 };
56
57 #define NUM_FAN_FDS ARRAY_SIZE(mark_cmds)
58
FIXTURE(fanotify)59 FIXTURE(fanotify) {
60 int fan_fd[NUM_FAN_FDS];
61 char buf[256];
62 unsigned int rem;
63 void *next;
64 char root_mntpoint[sizeof(root_mntpoint_templ)];
65 int orig_root;
66 int ns_fd;
67 uint64_t root_id;
68 };
69
FIXTURE_SETUP(fanotify)70 FIXTURE_SETUP(fanotify)
71 {
72 int i, ret;
73
74 ASSERT_EQ(unshare(CLONE_NEWNS), 0);
75
76 self->ns_fd = open("/proc/self/ns/mnt", O_RDONLY);
77 ASSERT_GE(self->ns_fd, 0);
78
79 ASSERT_EQ(mount("", "/", NULL, MS_REC|MS_PRIVATE, NULL), 0);
80
81 strcpy(self->root_mntpoint, root_mntpoint_templ);
82 ASSERT_NE(mkdtemp(self->root_mntpoint), NULL);
83
84 self->orig_root = open("/", O_PATH | O_CLOEXEC);
85 ASSERT_GE(self->orig_root, 0);
86
87 ASSERT_EQ(mount("tmpfs", self->root_mntpoint, "tmpfs", 0, NULL), 0);
88
89 ASSERT_EQ(chroot(self->root_mntpoint), 0);
90
91 ASSERT_EQ(chdir("/"), 0);
92
93 ASSERT_EQ(mkdir("a", 0700), 0);
94
95 ASSERT_EQ(mkdir("b", 0700), 0);
96
97 self->root_id = get_mnt_id(_metadata, "/");
98 ASSERT_NE(self->root_id, 0);
99
100 for (i = 0; i < NUM_FAN_FDS; i++) {
101 self->fan_fd[i] = fanotify_init(FAN_REPORT_MNT | FAN_NONBLOCK,
102 0);
103 ASSERT_GE(self->fan_fd[i], 0);
104 ret = fanotify_mark(self->fan_fd[i], FAN_MARK_ADD |
105 FAN_MARK_MNTNS,
106 FAN_MNT_ATTACH | FAN_MNT_DETACH,
107 self->ns_fd, NULL);
108 ASSERT_EQ(ret, 0);
109 // On fd[0] we do an extra ADD that changes nothing.
110 // On fd[1]/fd[2] we REMOVE/FLUSH which removes the mark.
111 ret = fanotify_mark(self->fan_fd[i], mark_cmds[i] |
112 FAN_MARK_MNTNS,
113 FAN_MNT_ATTACH | FAN_MNT_DETACH,
114 self->ns_fd, NULL);
115 ASSERT_EQ(ret, 0);
116 }
117
118 self->rem = 0;
119 }
120
FIXTURE_TEARDOWN(fanotify)121 FIXTURE_TEARDOWN(fanotify)
122 {
123 int i;
124
125 ASSERT_EQ(self->rem, 0);
126 for (i = 0; i < NUM_FAN_FDS; i++)
127 close(self->fan_fd[i]);
128
129 ASSERT_EQ(fchdir(self->orig_root), 0);
130
131 ASSERT_EQ(chroot("."), 0);
132
133 EXPECT_EQ(umount2(self->root_mntpoint, MNT_DETACH), 0);
134 EXPECT_EQ(chdir(self->root_mntpoint), 0);
135 EXPECT_EQ(chdir("/"), 0);
136 EXPECT_EQ(rmdir(self->root_mntpoint), 0);
137 }
138
expect_notify(struct __test_metadata * const _metadata,FIXTURE_DATA (fanotify)* self,uint64_t * mask)139 static uint64_t expect_notify(struct __test_metadata *const _metadata,
140 FIXTURE_DATA(fanotify) *self,
141 uint64_t *mask)
142 {
143 struct fanotify_event_metadata *meta;
144 struct fanotify_event_info_mnt *mnt;
145 unsigned int thislen;
146
147 if (!self->rem) {
148 ssize_t len;
149 int i;
150
151 for (i = NUM_FAN_FDS - 1; i >= 0; i--) {
152 len = read(self->fan_fd[i], self->buf,
153 sizeof(self->buf));
154 if (i > 0) {
155 // Groups 1,2 should get EAGAIN
156 ASSERT_EQ(len, -1);
157 ASSERT_EQ(errno, EAGAIN);
158 } else {
159 // Group 0 should get events
160 ASSERT_GT(len, 0);
161 }
162 }
163
164 self->rem = len;
165 self->next = (void *) self->buf;
166 }
167
168 meta = self->next;
169 ASSERT_TRUE(FAN_EVENT_OK(meta, self->rem));
170
171 thislen = meta->event_len;
172 self->rem -= thislen;
173 self->next += thislen;
174
175 *mask = meta->mask;
176 thislen -= sizeof(*meta);
177
178 mnt = ((void *) meta) + meta->event_len - thislen;
179
180 ASSERT_EQ(thislen, sizeof(*mnt));
181
182 return mnt->mnt_id;
183 }
184
expect_notify_n(struct __test_metadata * const _metadata,FIXTURE_DATA (fanotify)* self,unsigned int n,uint64_t mask[],uint64_t mnts[])185 static void expect_notify_n(struct __test_metadata *const _metadata,
186 FIXTURE_DATA(fanotify) *self,
187 unsigned int n, uint64_t mask[], uint64_t mnts[])
188 {
189 unsigned int i;
190
191 for (i = 0; i < n; i++)
192 mnts[i] = expect_notify(_metadata, self, &mask[i]);
193 }
194
expect_notify_mask(struct __test_metadata * const _metadata,FIXTURE_DATA (fanotify)* self,uint64_t expect_mask)195 static uint64_t expect_notify_mask(struct __test_metadata *const _metadata,
196 FIXTURE_DATA(fanotify) *self,
197 uint64_t expect_mask)
198 {
199 uint64_t mntid, mask;
200
201 mntid = expect_notify(_metadata, self, &mask);
202 ASSERT_EQ(expect_mask, mask);
203
204 return mntid;
205 }
206
207
expect_notify_mask_n(struct __test_metadata * const _metadata,FIXTURE_DATA (fanotify)* self,uint64_t mask,unsigned int n,uint64_t mnts[])208 static void expect_notify_mask_n(struct __test_metadata *const _metadata,
209 FIXTURE_DATA(fanotify) *self,
210 uint64_t mask, unsigned int n, uint64_t mnts[])
211 {
212 unsigned int i;
213
214 for (i = 0; i < n; i++)
215 mnts[i] = expect_notify_mask(_metadata, self, mask);
216 }
217
verify_mount_ids(struct __test_metadata * const _metadata,const uint64_t list1[],const uint64_t list2[],size_t num)218 static void verify_mount_ids(struct __test_metadata *const _metadata,
219 const uint64_t list1[], const uint64_t list2[],
220 size_t num)
221 {
222 unsigned int i, j;
223
224 // Check that neither list has any duplicates
225 for (i = 0; i < num; i++) {
226 for (j = 0; j < num; j++) {
227 if (i != j) {
228 ASSERT_NE(list1[i], list1[j]);
229 ASSERT_NE(list2[i], list2[j]);
230 }
231 }
232 }
233 // Check that all list1 memebers can be found in list2. Together with
234 // the above it means that the list1 and list2 represent the same sets.
235 for (i = 0; i < num; i++) {
236 for (j = 0; j < num; j++) {
237 if (list1[i] == list2[j])
238 break;
239 }
240 ASSERT_NE(j, num);
241 }
242 }
243
check_mounted(struct __test_metadata * const _metadata,const uint64_t mnts[],size_t num)244 static void check_mounted(struct __test_metadata *const _metadata,
245 const uint64_t mnts[], size_t num)
246 {
247 ssize_t ret;
248 uint64_t *list;
249
250 list = malloc((num + 1) * sizeof(list[0]));
251 ASSERT_NE(list, NULL);
252
253 ret = listmount(LSMT_ROOT, 0, 0, list, num + 1, 0);
254 ASSERT_EQ(ret, num);
255
256 verify_mount_ids(_metadata, mnts, list, num);
257
258 free(list);
259 }
260
setup_mount_tree(struct __test_metadata * const _metadata,int log2_num)261 static void setup_mount_tree(struct __test_metadata *const _metadata,
262 int log2_num)
263 {
264 int ret, i;
265
266 ret = mount("", "/", NULL, MS_SHARED, NULL);
267 ASSERT_EQ(ret, 0);
268
269 for (i = 0; i < log2_num; i++) {
270 ret = mount("/", "/", NULL, MS_BIND, NULL);
271 ASSERT_EQ(ret, 0);
272 }
273 }
274
TEST_F(fanotify,bind)275 TEST_F(fanotify, bind)
276 {
277 int ret;
278 uint64_t mnts[2] = { self->root_id };
279
280 ret = mount("/", "/", NULL, MS_BIND, NULL);
281 ASSERT_EQ(ret, 0);
282
283 mnts[1] = expect_notify_mask(_metadata, self, FAN_MNT_ATTACH);
284 ASSERT_NE(mnts[0], mnts[1]);
285
286 check_mounted(_metadata, mnts, 2);
287
288 // Cleanup
289 uint64_t detach_id;
290 ret = umount("/");
291 ASSERT_EQ(ret, 0);
292
293 detach_id = expect_notify_mask(_metadata, self, FAN_MNT_DETACH);
294 ASSERT_EQ(detach_id, mnts[1]);
295
296 check_mounted(_metadata, mnts, 1);
297 }
298
TEST_F(fanotify,move)299 TEST_F(fanotify, move)
300 {
301 int ret;
302 uint64_t mnts[2] = { self->root_id };
303 uint64_t move_id;
304
305 ret = mount("/", "/a", NULL, MS_BIND, NULL);
306 ASSERT_EQ(ret, 0);
307
308 mnts[1] = expect_notify_mask(_metadata, self, FAN_MNT_ATTACH);
309 ASSERT_NE(mnts[0], mnts[1]);
310
311 check_mounted(_metadata, mnts, 2);
312
313 ret = move_mount(AT_FDCWD, "/a", AT_FDCWD, "/b", 0);
314 ASSERT_EQ(ret, 0);
315
316 move_id = expect_notify_mask(_metadata, self, FAN_MNT_ATTACH | FAN_MNT_DETACH);
317 ASSERT_EQ(move_id, mnts[1]);
318
319 // Cleanup
320 ret = umount("/b");
321 ASSERT_EQ(ret, 0);
322
323 check_mounted(_metadata, mnts, 1);
324 }
325
TEST_F(fanotify,propagate)326 TEST_F(fanotify, propagate)
327 {
328 const unsigned int log2_num = 4;
329 const unsigned int num = (1 << log2_num);
330 uint64_t mnts[num];
331
332 setup_mount_tree(_metadata, log2_num);
333
334 expect_notify_mask_n(_metadata, self, FAN_MNT_ATTACH, num - 1, mnts + 1);
335
336 mnts[0] = self->root_id;
337 check_mounted(_metadata, mnts, num);
338
339 // Cleanup
340 int ret;
341 uint64_t mnts2[num];
342 ret = umount2("/", MNT_DETACH);
343 ASSERT_EQ(ret, 0);
344
345 ret = mount("", "/", NULL, MS_PRIVATE, NULL);
346 ASSERT_EQ(ret, 0);
347
348 mnts2[0] = self->root_id;
349 expect_notify_mask_n(_metadata, self, FAN_MNT_DETACH, num - 1, mnts2 + 1);
350 verify_mount_ids(_metadata, mnts, mnts2, num);
351
352 check_mounted(_metadata, mnts, 1);
353 }
354
TEST_F(fanotify,fsmount)355 TEST_F(fanotify, fsmount)
356 {
357 int ret, fs, mnt;
358 uint64_t mnts[2] = { self->root_id };
359
360 fs = fsopen("tmpfs", 0);
361 ASSERT_GE(fs, 0);
362
363 ret = fsconfig(fs, FSCONFIG_CMD_CREATE, 0, 0, 0);
364 ASSERT_EQ(ret, 0);
365
366 mnt = fsmount(fs, 0, 0);
367 ASSERT_GE(mnt, 0);
368
369 close(fs);
370
371 ret = move_mount(mnt, "", AT_FDCWD, "/a", MOVE_MOUNT_F_EMPTY_PATH);
372 ASSERT_EQ(ret, 0);
373
374 close(mnt);
375
376 mnts[1] = expect_notify_mask(_metadata, self, FAN_MNT_ATTACH);
377 ASSERT_NE(mnts[0], mnts[1]);
378
379 check_mounted(_metadata, mnts, 2);
380
381 // Cleanup
382 uint64_t detach_id;
383 ret = umount("/a");
384 ASSERT_EQ(ret, 0);
385
386 detach_id = expect_notify_mask(_metadata, self, FAN_MNT_DETACH);
387 ASSERT_EQ(detach_id, mnts[1]);
388
389 check_mounted(_metadata, mnts, 1);
390 }
391
TEST_F(fanotify,reparent)392 TEST_F(fanotify, reparent)
393 {
394 uint64_t mnts[6] = { self->root_id };
395 uint64_t dmnts[3];
396 uint64_t masks[3];
397 unsigned int i;
398 int ret;
399
400 // Create setup with a[1] -> b[2] propagation
401 ret = mount("/", "/a", NULL, MS_BIND, NULL);
402 ASSERT_EQ(ret, 0);
403
404 ret = mount("", "/a", NULL, MS_SHARED, NULL);
405 ASSERT_EQ(ret, 0);
406
407 ret = mount("/a", "/b", NULL, MS_BIND, NULL);
408 ASSERT_EQ(ret, 0);
409
410 ret = mount("", "/b", NULL, MS_SLAVE, NULL);
411 ASSERT_EQ(ret, 0);
412
413 expect_notify_mask_n(_metadata, self, FAN_MNT_ATTACH, 2, mnts + 1);
414
415 check_mounted(_metadata, mnts, 3);
416
417 // Mount on a[3], which is propagated to b[4]
418 ret = mount("/", "/a", NULL, MS_BIND, NULL);
419 ASSERT_EQ(ret, 0);
420
421 expect_notify_mask_n(_metadata, self, FAN_MNT_ATTACH, 2, mnts + 3);
422
423 check_mounted(_metadata, mnts, 5);
424
425 // Mount on b[5], not propagated
426 ret = mount("/", "/b", NULL, MS_BIND, NULL);
427 ASSERT_EQ(ret, 0);
428
429 mnts[5] = expect_notify_mask(_metadata, self, FAN_MNT_ATTACH);
430
431 check_mounted(_metadata, mnts, 6);
432
433 // Umount a[3], which is propagated to b[4], but not b[5]
434 // This will result in b[5] "falling" on b[2]
435 ret = umount("/a");
436 ASSERT_EQ(ret, 0);
437
438 expect_notify_n(_metadata, self, 3, masks, dmnts);
439 verify_mount_ids(_metadata, mnts + 3, dmnts, 3);
440
441 for (i = 0; i < 3; i++) {
442 if (dmnts[i] == mnts[5]) {
443 ASSERT_EQ(masks[i], FAN_MNT_ATTACH | FAN_MNT_DETACH);
444 } else {
445 ASSERT_EQ(masks[i], FAN_MNT_DETACH);
446 }
447 }
448
449 mnts[3] = mnts[5];
450 check_mounted(_metadata, mnts, 4);
451
452 // Cleanup
453 ret = umount("/b");
454 ASSERT_EQ(ret, 0);
455
456 ret = umount("/a");
457 ASSERT_EQ(ret, 0);
458
459 ret = umount("/b");
460 ASSERT_EQ(ret, 0);
461
462 expect_notify_mask_n(_metadata, self, FAN_MNT_DETACH, 3, dmnts);
463 verify_mount_ids(_metadata, mnts + 1, dmnts, 3);
464
465 check_mounted(_metadata, mnts, 1);
466 }
467
TEST_F(fanotify,rmdir)468 TEST_F(fanotify, rmdir)
469 {
470 uint64_t mnts[3] = { self->root_id };
471 int ret;
472
473 ret = mount("/", "/a", NULL, MS_BIND, NULL);
474 ASSERT_EQ(ret, 0);
475
476 ret = mount("/", "/a/b", NULL, MS_BIND, NULL);
477 ASSERT_EQ(ret, 0);
478
479 expect_notify_mask_n(_metadata, self, FAN_MNT_ATTACH, 2, mnts + 1);
480
481 check_mounted(_metadata, mnts, 3);
482
483 ret = chdir("/a");
484 ASSERT_EQ(ret, 0);
485
486 ret = fork();
487 ASSERT_GE(ret, 0);
488
489 if (ret == 0) {
490 chdir("/");
491 unshare(CLONE_NEWNS);
492 mount("", "/", NULL, MS_REC|MS_PRIVATE, NULL);
493 umount2("/a", MNT_DETACH);
494 // This triggers a detach in the other namespace
495 rmdir("/a");
496 exit(0);
497 }
498 wait(NULL);
499
500 expect_notify_mask_n(_metadata, self, FAN_MNT_DETACH, 2, mnts + 1);
501 check_mounted(_metadata, mnts, 1);
502
503 // Cleanup
504 ret = chdir("/");
505 ASSERT_EQ(ret, 0);
506 }
507
TEST_F(fanotify,pivot_root)508 TEST_F(fanotify, pivot_root)
509 {
510 uint64_t mnts[3] = { self->root_id };
511 uint64_t mnts2[3];
512 int ret;
513
514 ret = mount("tmpfs", "/a", "tmpfs", 0, NULL);
515 ASSERT_EQ(ret, 0);
516
517 mnts[2] = expect_notify_mask(_metadata, self, FAN_MNT_ATTACH);
518
519 ret = mkdir("/a/new", 0700);
520 ASSERT_EQ(ret, 0);
521
522 ret = mkdir("/a/old", 0700);
523 ASSERT_EQ(ret, 0);
524
525 ret = mount("/a", "/a/new", NULL, MS_BIND, NULL);
526 ASSERT_EQ(ret, 0);
527
528 mnts[1] = expect_notify_mask(_metadata, self, FAN_MNT_ATTACH);
529 check_mounted(_metadata, mnts, 3);
530
531 ret = syscall(SYS_pivot_root, "/a/new", "/a/new/old");
532 ASSERT_EQ(ret, 0);
533
534 expect_notify_mask_n(_metadata, self, FAN_MNT_ATTACH | FAN_MNT_DETACH, 2, mnts2);
535 verify_mount_ids(_metadata, mnts, mnts2, 2);
536 check_mounted(_metadata, mnts, 3);
537
538 // Cleanup
539 ret = syscall(SYS_pivot_root, "/old", "/old/a/new");
540 ASSERT_EQ(ret, 0);
541
542 ret = umount("/a/new");
543 ASSERT_EQ(ret, 0);
544
545 ret = umount("/a");
546 ASSERT_EQ(ret, 0);
547
548 check_mounted(_metadata, mnts, 1);
549 }
550
551 TEST_HARNESS_MAIN
552