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41669317 LP |
1 | /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/ |
2 | ||
3 | /*** | |
4 | This file is part of systemd. | |
5 | ||
6 | Copyright 2012 Harald Hoyer, Lennart Poettering | |
7 | ||
8 | systemd is free software; you can redistribute it and/or modify it | |
9 | under the terms of the GNU Lesser General Public License as published by | |
10 | the Free Software Foundation; either version 2.1 of the License, or | |
11 | (at your option) any later version. | |
12 | ||
13 | systemd is distributed in the hope that it will be useful, but | |
14 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
16 | Lesser General Public License for more details. | |
17 | ||
18 | You should have received a copy of the GNU Lesser General Public License | |
19 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
20 | ***/ | |
21 | ||
22 | #include <sys/stat.h> | |
23 | #include <stdbool.h> | |
24 | #include <errno.h> | |
25 | #include <string.h> | |
26 | #include <sys/mount.h> | |
27 | #include <unistd.h> | |
28 | #include <fcntl.h> | |
29 | ||
30 | #include "util.h" | |
31 | #include "path-util.h" | |
32 | #include "switch-root.h" | |
33 | ||
34 | int switch_root(const char *new_root) { | |
35 | ||
36 | /* Don't try to unmount/move the old "/", there's no way to do it. */ | |
37 | static const char move_mounts[] = | |
38 | "/dev\0" | |
39 | "/proc\0" | |
40 | "/sys\0" | |
41 | "/run\0"; | |
42 | ||
43 | int r, old_root_fd = -1; | |
44 | struct stat new_root_stat; | |
45 | bool old_root_remove; | |
46 | const char *i; | |
47 | ||
48 | if (path_equal(new_root, "/")) | |
49 | return 0; | |
50 | ||
51 | old_root_remove = in_initrd(); | |
52 | ||
53 | if (stat(new_root, &new_root_stat) < 0) { | |
54 | r = -errno; | |
55 | log_error("Failed to stat directory %s: %m", new_root); | |
56 | goto fail; | |
57 | } | |
58 | ||
f47fc355 LP |
59 | /* Work-around for a kernel bug: for some reason the kernel |
60 | * refuses switching root if any file systems are mounted | |
61 | * MS_SHARED. Hence remount them MS_PRIVATE here as a | |
62 | * work-around. | |
63 | * | |
64 | * https://bugzilla.redhat.com/show_bug.cgi?id=847418 */ | |
65 | if (mount(NULL, "/", NULL, MS_REC|MS_PRIVATE, NULL) < 0) | |
66 | log_warning("Failed to make \"/\" private mount: %m"); | |
67 | ||
41669317 LP |
68 | NULSTR_FOREACH(i, move_mounts) { |
69 | char new_mount[PATH_MAX]; | |
70 | struct stat sb; | |
71 | ||
72 | snprintf(new_mount, sizeof(new_mount), "%s%s", new_root, i); | |
73 | char_array_0(new_mount); | |
74 | ||
75 | if ((stat(new_mount, &sb) < 0) || | |
76 | sb.st_dev != new_root_stat.st_dev) { | |
77 | ||
78 | /* Mount point seems to be mounted already or | |
79 | * stat failed. Unmount the old mount | |
80 | * point. */ | |
81 | if (umount2(i, MNT_DETACH) < 0) | |
82 | log_warning("Failed to unmount %s: %m", i); | |
83 | continue; | |
84 | } | |
85 | ||
86 | if (mount(i, new_mount, NULL, MS_MOVE, NULL) < 0) { | |
87 | log_error("Failed to move mount %s to %s, forcing unmount: %m", i, new_mount); | |
88 | ||
89 | if (umount2(i, MNT_FORCE) < 0) | |
90 | log_warning("Failed to unmount %s: %m", i); | |
91 | } | |
92 | } | |
93 | ||
94 | if (chdir(new_root) < 0) { | |
95 | r = -errno; | |
96 | log_error("Failed to change directory to %s: %m", new_root); | |
97 | goto fail; | |
98 | } | |
99 | ||
100 | if (old_root_remove) { | |
101 | old_root_fd = open("/", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_NOCTTY|O_DIRECTORY); | |
102 | if (old_root_fd < 0) | |
103 | log_warning("Failed to open root directory: %m"); | |
104 | } | |
105 | ||
106 | if (mount(new_root, "/", NULL, MS_MOVE, NULL) < 0) { | |
107 | r = -errno; | |
108 | log_error("Failed to mount moving %s to /: %m", new_root); | |
109 | goto fail; | |
110 | } | |
111 | ||
112 | if (chroot(".") < 0) { | |
113 | r = -errno; | |
114 | log_error("Failed to change root: %m"); | |
115 | goto fail; | |
116 | } | |
117 | ||
118 | if (old_root_fd >= 0) { | |
119 | struct stat rb; | |
120 | ||
121 | if (fstat(old_root_fd, &rb) < 0) | |
122 | log_warning("Failed to stat old root directory, leaving: %m"); | |
b46178e5 | 123 | else { |
41669317 | 124 | rm_rf_children(old_root_fd, false, false, &rb); |
b46178e5 HH |
125 | old_root_fd = -1; |
126 | } | |
41669317 LP |
127 | } |
128 | ||
129 | r = 0; | |
130 | ||
131 | fail: | |
132 | if (old_root_fd >= 0) | |
133 | close_nointr_nofail(old_root_fd); | |
134 | ||
135 | return r; | |
136 | } |