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linux/tools/testing/selftests/filesystems/mount-notify/mount-notify_test.c
Amir Goldstein e897b9b133
selftests/filesystems: create get_unique_mnt_id() helper 
Add helper to utils.c and use it in mount-notify and statmount tests.

Linking with utils.c drags in a dependecy with libcap, so add it to the
Makefile of the tests.

Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Link: https://lore.kernel.org/20250509133240.529330-7-amir73il@gmail.com
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
2025-05-12 11:40:12 +02:00

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// SPDX-License-Identifier: GPL-2.0-or-later
// Copyright (c) 2025 Miklos Szeredi <miklos@szeredi.hu>
#define _GNU_SOURCE
#include <fcntl.h>
#include <sched.h>
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/mount.h>
#include <unistd.h>
#include <sys/syscall.h>
#include "../../kselftest_harness.h"
#include "../statmount/statmount.h"
#include "../utils.h"
// Needed for linux/fanotify.h
#ifndef __kernel_fsid_t
typedef struct {
int val[2];
} __kernel_fsid_t;
#endif
#include <sys/fanotify.h>
static const char root_mntpoint_templ[] = "/tmp/mount-notify_test_root.XXXXXX";
static const int mark_cmds[] = {
FAN_MARK_ADD,
FAN_MARK_REMOVE,
FAN_MARK_FLUSH
};
#define NUM_FAN_FDS ARRAY_SIZE(mark_cmds)
FIXTURE(fanotify) {
int fan_fd[NUM_FAN_FDS];
char buf[256];
unsigned int rem;
void *next;
char root_mntpoint[sizeof(root_mntpoint_templ)];
int orig_root;
int ns_fd;
uint64_t root_id;
};
FIXTURE_SETUP(fanotify)
{
int i, ret;
ASSERT_EQ(unshare(CLONE_NEWNS), 0);
self->ns_fd = open("/proc/self/ns/mnt", O_RDONLY);
ASSERT_GE(self->ns_fd, 0);
ASSERT_EQ(mount("", "/", NULL, MS_REC|MS_PRIVATE, NULL), 0);
strcpy(self->root_mntpoint, root_mntpoint_templ);
ASSERT_NE(mkdtemp(self->root_mntpoint), NULL);
self->orig_root = open("/", O_PATH | O_CLOEXEC);
ASSERT_GE(self->orig_root, 0);
ASSERT_EQ(mount("tmpfs", self->root_mntpoint, "tmpfs", 0, NULL), 0);
ASSERT_EQ(chroot(self->root_mntpoint), 0);
ASSERT_EQ(chdir("/"), 0);
ASSERT_EQ(mkdir("a", 0700), 0);
ASSERT_EQ(mkdir("b", 0700), 0);
self->root_id = get_unique_mnt_id("/");
ASSERT_NE(self->root_id, 0);
for (i = 0; i < NUM_FAN_FDS; i++) {
self->fan_fd[i] = fanotify_init(FAN_REPORT_MNT | FAN_NONBLOCK,
0);
ASSERT_GE(self->fan_fd[i], 0);
ret = fanotify_mark(self->fan_fd[i], FAN_MARK_ADD |
FAN_MARK_MNTNS,
FAN_MNT_ATTACH | FAN_MNT_DETACH,
self->ns_fd, NULL);
ASSERT_EQ(ret, 0);
// On fd[0] we do an extra ADD that changes nothing.
// On fd[1]/fd[2] we REMOVE/FLUSH which removes the mark.
ret = fanotify_mark(self->fan_fd[i], mark_cmds[i] |
FAN_MARK_MNTNS,
FAN_MNT_ATTACH | FAN_MNT_DETACH,
self->ns_fd, NULL);
ASSERT_EQ(ret, 0);
}
self->rem = 0;
}
FIXTURE_TEARDOWN(fanotify)
{
int i;
ASSERT_EQ(self->rem, 0);
for (i = 0; i < NUM_FAN_FDS; i++)
close(self->fan_fd[i]);
ASSERT_EQ(fchdir(self->orig_root), 0);
ASSERT_EQ(chroot("."), 0);
EXPECT_EQ(umount2(self->root_mntpoint, MNT_DETACH), 0);
EXPECT_EQ(chdir(self->root_mntpoint), 0);
EXPECT_EQ(chdir("/"), 0);
EXPECT_EQ(rmdir(self->root_mntpoint), 0);
}
static uint64_t expect_notify(struct __test_metadata *const _metadata,
FIXTURE_DATA(fanotify) *self,
uint64_t *mask)
{
struct fanotify_event_metadata *meta;
struct fanotify_event_info_mnt *mnt;
unsigned int thislen;
if (!self->rem) {
ssize_t len;
int i;
for (i = NUM_FAN_FDS - 1; i >= 0; i--) {
len = read(self->fan_fd[i], self->buf,
sizeof(self->buf));
if (i > 0) {
// Groups 1,2 should get EAGAIN
ASSERT_EQ(len, -1);
ASSERT_EQ(errno, EAGAIN);
} else {
// Group 0 should get events
ASSERT_GT(len, 0);
}
}
self->rem = len;
self->next = (void *) self->buf;
}
meta = self->next;
ASSERT_TRUE(FAN_EVENT_OK(meta, self->rem));
thislen = meta->event_len;
self->rem -= thislen;
self->next += thislen;
*mask = meta->mask;
thislen -= sizeof(*meta);
mnt = ((void *) meta) + meta->event_len - thislen;
ASSERT_EQ(thislen, sizeof(*mnt));
return mnt->mnt_id;
}
static void expect_notify_n(struct __test_metadata *const _metadata,
FIXTURE_DATA(fanotify) *self,
unsigned int n, uint64_t mask[], uint64_t mnts[])
{
unsigned int i;
for (i = 0; i < n; i++)
mnts[i] = expect_notify(_metadata, self, &mask[i]);
}
static uint64_t expect_notify_mask(struct __test_metadata *const _metadata,
FIXTURE_DATA(fanotify) *self,
uint64_t expect_mask)
{
uint64_t mntid, mask;
mntid = expect_notify(_metadata, self, &mask);
ASSERT_EQ(expect_mask, mask);
return mntid;
}
static void expect_notify_mask_n(struct __test_metadata *const _metadata,
FIXTURE_DATA(fanotify) *self,
uint64_t mask, unsigned int n, uint64_t mnts[])
{
unsigned int i;
for (i = 0; i < n; i++)
mnts[i] = expect_notify_mask(_metadata, self, mask);
}
static void verify_mount_ids(struct __test_metadata *const _metadata,
const uint64_t list1[], const uint64_t list2[],
size_t num)
{
unsigned int i, j;
// Check that neither list has any duplicates
for (i = 0; i < num; i++) {
for (j = 0; j < num; j++) {
if (i != j) {
ASSERT_NE(list1[i], list1[j]);
ASSERT_NE(list2[i], list2[j]);
}
}
}
// Check that all list1 memebers can be found in list2. Together with
// the above it means that the list1 and list2 represent the same sets.
for (i = 0; i < num; i++) {
for (j = 0; j < num; j++) {
if (list1[i] == list2[j])
break;
}
ASSERT_NE(j, num);
}
}
static void check_mounted(struct __test_metadata *const _metadata,
const uint64_t mnts[], size_t num)
{
ssize_t ret;
uint64_t *list;
list = malloc((num + 1) * sizeof(list[0]));
ASSERT_NE(list, NULL);
ret = listmount(LSMT_ROOT, 0, 0, list, num + 1, 0);
ASSERT_EQ(ret, num);
verify_mount_ids(_metadata, mnts, list, num);
free(list);
}
static void setup_mount_tree(struct __test_metadata *const _metadata,
int log2_num)
{
int ret, i;
ret = mount("", "/", NULL, MS_SHARED, NULL);
ASSERT_EQ(ret, 0);
for (i = 0; i < log2_num; i++) {
ret = mount("/", "/", NULL, MS_BIND, NULL);
ASSERT_EQ(ret, 0);
}
}
TEST_F(fanotify, bind)
{
int ret;
uint64_t mnts[2] = { self->root_id };
ret = mount("/", "/", NULL, MS_BIND, NULL);
ASSERT_EQ(ret, 0);
mnts[1] = expect_notify_mask(_metadata, self, FAN_MNT_ATTACH);
ASSERT_NE(mnts[0], mnts[1]);
check_mounted(_metadata, mnts, 2);
// Cleanup
uint64_t detach_id;
ret = umount("/");
ASSERT_EQ(ret, 0);
detach_id = expect_notify_mask(_metadata, self, FAN_MNT_DETACH);
ASSERT_EQ(detach_id, mnts[1]);
check_mounted(_metadata, mnts, 1);
}
TEST_F(fanotify, move)
{
int ret;
uint64_t mnts[2] = { self->root_id };
uint64_t move_id;
ret = mount("/", "/a", NULL, MS_BIND, NULL);
ASSERT_EQ(ret, 0);
mnts[1] = expect_notify_mask(_metadata, self, FAN_MNT_ATTACH);
ASSERT_NE(mnts[0], mnts[1]);
check_mounted(_metadata, mnts, 2);
ret = move_mount(AT_FDCWD, "/a", AT_FDCWD, "/b", 0);
ASSERT_EQ(ret, 0);
move_id = expect_notify_mask(_metadata, self, FAN_MNT_ATTACH | FAN_MNT_DETACH);
ASSERT_EQ(move_id, mnts[1]);
// Cleanup
ret = umount("/b");
ASSERT_EQ(ret, 0);
check_mounted(_metadata, mnts, 1);
}
TEST_F(fanotify, propagate)
{
const unsigned int log2_num = 4;
const unsigned int num = (1 << log2_num);
uint64_t mnts[num];
setup_mount_tree(_metadata, log2_num);
expect_notify_mask_n(_metadata, self, FAN_MNT_ATTACH, num - 1, mnts + 1);
mnts[0] = self->root_id;
check_mounted(_metadata, mnts, num);
// Cleanup
int ret;
uint64_t mnts2[num];
ret = umount2("/", MNT_DETACH);
ASSERT_EQ(ret, 0);
ret = mount("", "/", NULL, MS_PRIVATE, NULL);
ASSERT_EQ(ret, 0);
mnts2[0] = self->root_id;
expect_notify_mask_n(_metadata, self, FAN_MNT_DETACH, num - 1, mnts2 + 1);
verify_mount_ids(_metadata, mnts, mnts2, num);
check_mounted(_metadata, mnts, 1);
}
TEST_F(fanotify, fsmount)
{
int ret, fs, mnt;
uint64_t mnts[2] = { self->root_id };
fs = fsopen("tmpfs", 0);
ASSERT_GE(fs, 0);
ret = fsconfig(fs, FSCONFIG_CMD_CREATE, 0, 0, 0);
ASSERT_EQ(ret, 0);
mnt = fsmount(fs, 0, 0);
ASSERT_GE(mnt, 0);
close(fs);
ret = move_mount(mnt, "", AT_FDCWD, "/a", MOVE_MOUNT_F_EMPTY_PATH);
ASSERT_EQ(ret, 0);
close(mnt);
mnts[1] = expect_notify_mask(_metadata, self, FAN_MNT_ATTACH);
ASSERT_NE(mnts[0], mnts[1]);
check_mounted(_metadata, mnts, 2);
// Cleanup
uint64_t detach_id;
ret = umount("/a");
ASSERT_EQ(ret, 0);
detach_id = expect_notify_mask(_metadata, self, FAN_MNT_DETACH);
ASSERT_EQ(detach_id, mnts[1]);
check_mounted(_metadata, mnts, 1);
}
TEST_F(fanotify, reparent)
{
uint64_t mnts[6] = { self->root_id };
uint64_t dmnts[3];
uint64_t masks[3];
unsigned int i;
int ret;
// Create setup with a[1] -> b[2] propagation
ret = mount("/", "/a", NULL, MS_BIND, NULL);
ASSERT_EQ(ret, 0);
ret = mount("", "/a", NULL, MS_SHARED, NULL);
ASSERT_EQ(ret, 0);
ret = mount("/a", "/b", NULL, MS_BIND, NULL);
ASSERT_EQ(ret, 0);
ret = mount("", "/b", NULL, MS_SLAVE, NULL);
ASSERT_EQ(ret, 0);
expect_notify_mask_n(_metadata, self, FAN_MNT_ATTACH, 2, mnts + 1);
check_mounted(_metadata, mnts, 3);
// Mount on a[3], which is propagated to b[4]
ret = mount("/", "/a", NULL, MS_BIND, NULL);
ASSERT_EQ(ret, 0);
expect_notify_mask_n(_metadata, self, FAN_MNT_ATTACH, 2, mnts + 3);
check_mounted(_metadata, mnts, 5);
// Mount on b[5], not propagated
ret = mount("/", "/b", NULL, MS_BIND, NULL);
ASSERT_EQ(ret, 0);
mnts[5] = expect_notify_mask(_metadata, self, FAN_MNT_ATTACH);
check_mounted(_metadata, mnts, 6);
// Umount a[3], which is propagated to b[4], but not b[5]
// This will result in b[5] "falling" on b[2]
ret = umount("/a");
ASSERT_EQ(ret, 0);
expect_notify_n(_metadata, self, 3, masks, dmnts);
verify_mount_ids(_metadata, mnts + 3, dmnts, 3);
for (i = 0; i < 3; i++) {
if (dmnts[i] == mnts[5]) {
ASSERT_EQ(masks[i], FAN_MNT_ATTACH | FAN_MNT_DETACH);
} else {
ASSERT_EQ(masks[i], FAN_MNT_DETACH);
}
}
mnts[3] = mnts[5];
check_mounted(_metadata, mnts, 4);
// Cleanup
ret = umount("/b");
ASSERT_EQ(ret, 0);
ret = umount("/a");
ASSERT_EQ(ret, 0);
ret = umount("/b");
ASSERT_EQ(ret, 0);
expect_notify_mask_n(_metadata, self, FAN_MNT_DETACH, 3, dmnts);
verify_mount_ids(_metadata, mnts + 1, dmnts, 3);
check_mounted(_metadata, mnts, 1);
}
TEST_F(fanotify, rmdir)
{
uint64_t mnts[3] = { self->root_id };
int ret;
ret = mount("/", "/a", NULL, MS_BIND, NULL);
ASSERT_EQ(ret, 0);
ret = mount("/", "/a/b", NULL, MS_BIND, NULL);
ASSERT_EQ(ret, 0);
expect_notify_mask_n(_metadata, self, FAN_MNT_ATTACH, 2, mnts + 1);
check_mounted(_metadata, mnts, 3);
ret = chdir("/a");
ASSERT_EQ(ret, 0);
ret = fork();
ASSERT_GE(ret, 0);
if (ret == 0) {
chdir("/");
unshare(CLONE_NEWNS);
mount("", "/", NULL, MS_REC|MS_PRIVATE, NULL);
umount2("/a", MNT_DETACH);
// This triggers a detach in the other namespace
rmdir("/a");
exit(0);
}
wait(NULL);
expect_notify_mask_n(_metadata, self, FAN_MNT_DETACH, 2, mnts + 1);
check_mounted(_metadata, mnts, 1);
// Cleanup
ret = chdir("/");
ASSERT_EQ(ret, 0);
}
TEST_F(fanotify, pivot_root)
{
uint64_t mnts[3] = { self->root_id };
uint64_t mnts2[3];
int ret;
ret = mount("tmpfs", "/a", "tmpfs", 0, NULL);
ASSERT_EQ(ret, 0);
mnts[2] = expect_notify_mask(_metadata, self, FAN_MNT_ATTACH);
ret = mkdir("/a/new", 0700);
ASSERT_EQ(ret, 0);
ret = mkdir("/a/old", 0700);
ASSERT_EQ(ret, 0);
ret = mount("/a", "/a/new", NULL, MS_BIND, NULL);
ASSERT_EQ(ret, 0);
mnts[1] = expect_notify_mask(_metadata, self, FAN_MNT_ATTACH);
check_mounted(_metadata, mnts, 3);
ret = syscall(SYS_pivot_root, "/a/new", "/a/new/old");
ASSERT_EQ(ret, 0);
expect_notify_mask_n(_metadata, self, FAN_MNT_ATTACH | FAN_MNT_DETACH, 2, mnts2);
verify_mount_ids(_metadata, mnts, mnts2, 2);
check_mounted(_metadata, mnts, 3);
// Cleanup
ret = syscall(SYS_pivot_root, "/old", "/old/a/new");
ASSERT_EQ(ret, 0);
ret = umount("/a/new");
ASSERT_EQ(ret, 0);
ret = umount("/a");
ASSERT_EQ(ret, 0);
check_mounted(_metadata, mnts, 1);
}
TEST_HARNESS_MAIN
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