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663996b3 MS |
1 | /*** |
2 | This file is part of systemd. | |
3 | ||
4 | Copyright 2012 Harald Hoyer, Lennart Poettering | |
5 | ||
6 | systemd is free software; you can redistribute it and/or modify it | |
7 | under the terms of the GNU Lesser General Public License as published by | |
8 | the Free Software Foundation; either version 2.1 of the License, or | |
9 | (at your option) any later version. | |
10 | ||
11 | systemd is distributed in the hope that it will be useful, but | |
12 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
14 | Lesser General Public License for more details. | |
15 | ||
16 | You should have received a copy of the GNU Lesser General Public License | |
17 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
18 | ***/ | |
19 | ||
663996b3 | 20 | #include <errno.h> |
db2df898 | 21 | #include <fcntl.h> |
4c89c718 | 22 | #include <limits.h> |
db2df898 | 23 | #include <stdbool.h> |
4c89c718 | 24 | #include <stdio.h> |
663996b3 | 25 | #include <sys/mount.h> |
db2df898 | 26 | #include <sys/stat.h> |
663996b3 | 27 | #include <unistd.h> |
663996b3 | 28 | |
e842803a | 29 | #include "base-filesystem.h" |
db2df898 | 30 | #include "fd-util.h" |
4c89c718 | 31 | #include "log.h" |
663996b3 | 32 | #include "missing.h" |
db2df898 MP |
33 | #include "mkdir.h" |
34 | #include "path-util.h" | |
35 | #include "rm-rf.h" | |
4c89c718 | 36 | #include "stdio-util.h" |
db2df898 | 37 | #include "string-util.h" |
e3bff60a | 38 | #include "switch-root.h" |
db2df898 MP |
39 | #include "user-util.h" |
40 | #include "util.h" | |
663996b3 | 41 | |
5eef597e | 42 | int switch_root(const char *new_root, const char *oldroot, bool detach_oldroot, unsigned long mountflags) { |
663996b3 MS |
43 | |
44 | /* Don't try to unmount/move the old "/", there's no way to do it. */ | |
45 | static const char move_mounts[] = | |
46 | "/dev\0" | |
47 | "/proc\0" | |
48 | "/sys\0" | |
49 | "/run\0"; | |
50 | ||
60f067b4 | 51 | _cleanup_close_ int old_root_fd = -1; |
663996b3 MS |
52 | struct stat new_root_stat; |
53 | bool old_root_remove; | |
60f067b4 | 54 | const char *i, *temporary_old_root; |
663996b3 MS |
55 | |
56 | if (path_equal(new_root, "/")) | |
57 | return 0; | |
58 | ||
e735f4d4 | 59 | temporary_old_root = strjoina(new_root, oldroot); |
5eef597e | 60 | mkdir_p_label(temporary_old_root, 0755); |
663996b3 MS |
61 | |
62 | old_root_remove = in_initrd(); | |
63 | ||
f47781d8 MP |
64 | if (stat(new_root, &new_root_stat) < 0) |
65 | return log_error_errno(errno, "Failed to stat directory %s: %m", new_root); | |
663996b3 | 66 | |
5eef597e MP |
67 | /* Work-around for kernel design: the kernel refuses switching |
68 | * root if any file systems are mounted MS_SHARED. Hence | |
69 | * remount them MS_PRIVATE here as a work-around. | |
663996b3 MS |
70 | * |
71 | * https://bugzilla.redhat.com/show_bug.cgi?id=847418 */ | |
72 | if (mount(NULL, "/", NULL, MS_REC|MS_PRIVATE, NULL) < 0) | |
f47781d8 | 73 | log_warning_errno(errno, "Failed to make \"/\" private mount: %m"); |
663996b3 MS |
74 | |
75 | NULSTR_FOREACH(i, move_mounts) { | |
76 | char new_mount[PATH_MAX]; | |
77 | struct stat sb; | |
78 | ||
4c89c718 | 79 | xsprintf(new_mount, "%s%s", new_root, i); |
663996b3 | 80 | |
5eef597e | 81 | mkdir_p_label(new_mount, 0755); |
e842803a | 82 | |
663996b3 MS |
83 | if ((stat(new_mount, &sb) < 0) || |
84 | sb.st_dev != new_root_stat.st_dev) { | |
85 | ||
86 | /* Mount point seems to be mounted already or | |
87 | * stat failed. Unmount the old mount | |
88 | * point. */ | |
89 | if (umount2(i, MNT_DETACH) < 0) | |
f47781d8 | 90 | log_warning_errno(errno, "Failed to unmount %s: %m", i); |
663996b3 MS |
91 | continue; |
92 | } | |
93 | ||
5eef597e MP |
94 | if (mount(i, new_mount, NULL, mountflags, NULL) < 0) { |
95 | if (mountflags & MS_MOVE) { | |
f47781d8 | 96 | log_error_errno(errno, "Failed to move mount %s to %s, forcing unmount: %m", i, new_mount); |
5eef597e MP |
97 | |
98 | if (umount2(i, MNT_FORCE) < 0) | |
f47781d8 | 99 | log_warning_errno(errno, "Failed to unmount %s: %m", i); |
5eef597e MP |
100 | } |
101 | if (mountflags & MS_BIND) | |
f47781d8 | 102 | log_error_errno(errno, "Failed to bind mount %s to %s: %m", i, new_mount); |
663996b3 | 103 | |
663996b3 MS |
104 | } |
105 | } | |
106 | ||
f47781d8 MP |
107 | /* Do not fail, if base_filesystem_create() fails. Not all |
108 | * switch roots are like base_filesystem_create() wants them | |
109 | * to look like. They might even boot, if they are RO and | |
110 | * don't have the FS layout. Just ignore the error and | |
111 | * switch_root() nevertheless. */ | |
e3bff60a | 112 | (void) base_filesystem_create(new_root, UID_INVALID, GID_INVALID); |
e842803a | 113 | |
f47781d8 MP |
114 | if (chdir(new_root) < 0) |
115 | return log_error_errno(errno, "Failed to change directory to %s: %m", new_root); | |
663996b3 MS |
116 | |
117 | if (old_root_remove) { | |
118 | old_root_fd = open("/", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_NOCTTY|O_DIRECTORY); | |
119 | if (old_root_fd < 0) | |
f47781d8 | 120 | log_warning_errno(errno, "Failed to open root directory: %m"); |
663996b3 MS |
121 | } |
122 | ||
123 | /* We first try a pivot_root() so that we can umount the old | |
124 | * root dir. In many cases (i.e. where rootfs is /), that's | |
125 | * not possible however, and hence we simply overmount root */ | |
126 | if (pivot_root(new_root, temporary_old_root) >= 0) { | |
127 | ||
5eef597e MP |
128 | /* Immediately get rid of the old root, if detach_oldroot is set. |
129 | * Since we are running off it we need to do this lazily. */ | |
130 | if (detach_oldroot && umount2(oldroot, MNT_DETACH) < 0) | |
f47781d8 | 131 | log_error_errno(errno, "Failed to lazily umount old root dir %s, %s: %m", |
5eef597e MP |
132 | oldroot, |
133 | errno == ENOENT ? "ignoring" : "leaving it around"); | |
663996b3 | 134 | |
f47781d8 MP |
135 | } else if (mount(new_root, "/", NULL, MS_MOVE, NULL) < 0) |
136 | return log_error_errno(errno, "Failed to mount moving %s to /: %m", new_root); | |
663996b3 | 137 | |
f47781d8 MP |
138 | if (chroot(".") < 0) |
139 | return log_error_errno(errno, "Failed to change root: %m"); | |
663996b3 | 140 | |
f47781d8 MP |
141 | if (chdir("/") < 0) |
142 | return log_error_errno(errno, "Failed to change directory: %m"); | |
663996b3 MS |
143 | |
144 | if (old_root_fd >= 0) { | |
145 | struct stat rb; | |
146 | ||
147 | if (fstat(old_root_fd, &rb) < 0) | |
f47781d8 | 148 | log_warning_errno(errno, "Failed to stat old root directory, leaving: %m"); |
663996b3 | 149 | else { |
e3bff60a | 150 | (void) rm_rf_children(old_root_fd, 0, &rb); |
663996b3 MS |
151 | old_root_fd = -1; |
152 | } | |
153 | } | |
154 | ||
60f067b4 | 155 | return 0; |
663996b3 | 156 | } |