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663996b3 MS |
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" | |
e842803a | 32 | #include "mkdir.h" |
e3bff60a | 33 | #include "rm-rf.h" |
e842803a | 34 | #include "base-filesystem.h" |
663996b3 | 35 | #include "missing.h" |
e3bff60a | 36 | #include "switch-root.h" |
663996b3 | 37 | |
5eef597e | 38 | int switch_root(const char *new_root, const char *oldroot, bool detach_oldroot, unsigned long mountflags) { |
663996b3 MS |
39 | |
40 | /* Don't try to unmount/move the old "/", there's no way to do it. */ | |
41 | static const char move_mounts[] = | |
42 | "/dev\0" | |
43 | "/proc\0" | |
44 | "/sys\0" | |
45 | "/run\0"; | |
46 | ||
60f067b4 | 47 | _cleanup_close_ int old_root_fd = -1; |
663996b3 MS |
48 | struct stat new_root_stat; |
49 | bool old_root_remove; | |
60f067b4 | 50 | const char *i, *temporary_old_root; |
663996b3 MS |
51 | |
52 | if (path_equal(new_root, "/")) | |
53 | return 0; | |
54 | ||
e735f4d4 | 55 | temporary_old_root = strjoina(new_root, oldroot); |
5eef597e | 56 | mkdir_p_label(temporary_old_root, 0755); |
663996b3 MS |
57 | |
58 | old_root_remove = in_initrd(); | |
59 | ||
f47781d8 MP |
60 | if (stat(new_root, &new_root_stat) < 0) |
61 | return log_error_errno(errno, "Failed to stat directory %s: %m", new_root); | |
663996b3 | 62 | |
5eef597e MP |
63 | /* Work-around for kernel design: the kernel refuses switching |
64 | * root if any file systems are mounted MS_SHARED. Hence | |
65 | * remount them MS_PRIVATE here as a work-around. | |
663996b3 MS |
66 | * |
67 | * https://bugzilla.redhat.com/show_bug.cgi?id=847418 */ | |
68 | if (mount(NULL, "/", NULL, MS_REC|MS_PRIVATE, NULL) < 0) | |
f47781d8 | 69 | log_warning_errno(errno, "Failed to make \"/\" private mount: %m"); |
663996b3 MS |
70 | |
71 | NULSTR_FOREACH(i, move_mounts) { | |
72 | char new_mount[PATH_MAX]; | |
73 | struct stat sb; | |
74 | ||
75 | snprintf(new_mount, sizeof(new_mount), "%s%s", new_root, i); | |
663996b3 | 76 | |
5eef597e | 77 | mkdir_p_label(new_mount, 0755); |
e842803a | 78 | |
663996b3 MS |
79 | if ((stat(new_mount, &sb) < 0) || |
80 | sb.st_dev != new_root_stat.st_dev) { | |
81 | ||
82 | /* Mount point seems to be mounted already or | |
83 | * stat failed. Unmount the old mount | |
84 | * point. */ | |
85 | if (umount2(i, MNT_DETACH) < 0) | |
f47781d8 | 86 | log_warning_errno(errno, "Failed to unmount %s: %m", i); |
663996b3 MS |
87 | continue; |
88 | } | |
89 | ||
5eef597e MP |
90 | if (mount(i, new_mount, NULL, mountflags, NULL) < 0) { |
91 | if (mountflags & MS_MOVE) { | |
f47781d8 | 92 | log_error_errno(errno, "Failed to move mount %s to %s, forcing unmount: %m", i, new_mount); |
5eef597e MP |
93 | |
94 | if (umount2(i, MNT_FORCE) < 0) | |
f47781d8 | 95 | log_warning_errno(errno, "Failed to unmount %s: %m", i); |
5eef597e MP |
96 | } |
97 | if (mountflags & MS_BIND) | |
f47781d8 | 98 | log_error_errno(errno, "Failed to bind mount %s to %s: %m", i, new_mount); |
663996b3 | 99 | |
663996b3 MS |
100 | } |
101 | } | |
102 | ||
f47781d8 MP |
103 | /* Do not fail, if base_filesystem_create() fails. Not all |
104 | * switch roots are like base_filesystem_create() wants them | |
105 | * to look like. They might even boot, if they are RO and | |
106 | * don't have the FS layout. Just ignore the error and | |
107 | * switch_root() nevertheless. */ | |
e3bff60a | 108 | (void) base_filesystem_create(new_root, UID_INVALID, GID_INVALID); |
e842803a | 109 | |
f47781d8 MP |
110 | if (chdir(new_root) < 0) |
111 | return log_error_errno(errno, "Failed to change directory to %s: %m", new_root); | |
663996b3 MS |
112 | |
113 | if (old_root_remove) { | |
114 | old_root_fd = open("/", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_NOCTTY|O_DIRECTORY); | |
115 | if (old_root_fd < 0) | |
f47781d8 | 116 | log_warning_errno(errno, "Failed to open root directory: %m"); |
663996b3 MS |
117 | } |
118 | ||
119 | /* We first try a pivot_root() so that we can umount the old | |
120 | * root dir. In many cases (i.e. where rootfs is /), that's | |
121 | * not possible however, and hence we simply overmount root */ | |
122 | if (pivot_root(new_root, temporary_old_root) >= 0) { | |
123 | ||
5eef597e MP |
124 | /* Immediately get rid of the old root, if detach_oldroot is set. |
125 | * Since we are running off it we need to do this lazily. */ | |
126 | if (detach_oldroot && umount2(oldroot, MNT_DETACH) < 0) | |
f47781d8 | 127 | log_error_errno(errno, "Failed to lazily umount old root dir %s, %s: %m", |
5eef597e MP |
128 | oldroot, |
129 | errno == ENOENT ? "ignoring" : "leaving it around"); | |
663996b3 | 130 | |
f47781d8 MP |
131 | } else if (mount(new_root, "/", NULL, MS_MOVE, NULL) < 0) |
132 | return log_error_errno(errno, "Failed to mount moving %s to /: %m", new_root); | |
663996b3 | 133 | |
f47781d8 MP |
134 | if (chroot(".") < 0) |
135 | return log_error_errno(errno, "Failed to change root: %m"); | |
663996b3 | 136 | |
f47781d8 MP |
137 | if (chdir("/") < 0) |
138 | return log_error_errno(errno, "Failed to change directory: %m"); | |
663996b3 MS |
139 | |
140 | if (old_root_fd >= 0) { | |
141 | struct stat rb; | |
142 | ||
143 | if (fstat(old_root_fd, &rb) < 0) | |
f47781d8 | 144 | log_warning_errno(errno, "Failed to stat old root directory, leaving: %m"); |
663996b3 | 145 | else { |
e3bff60a | 146 | (void) rm_rf_children(old_root_fd, 0, &rb); |
663996b3 MS |
147 | old_root_fd = -1; |
148 | } | |
149 | } | |
150 | ||
60f067b4 | 151 | return 0; |
663996b3 | 152 | } |