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Commit | Line | Data |
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53e1b683 | 1 | /* SPDX-License-Identifier: LGPL-2.1+ */ |
41669317 | 2 | |
41669317 | 3 | #include <errno.h> |
07630cea | 4 | #include <fcntl.h> |
a8fbdf54 | 5 | #include <limits.h> |
07630cea | 6 | #include <stdbool.h> |
41669317 | 7 | #include <sys/mount.h> |
07630cea | 8 | #include <sys/stat.h> |
41669317 | 9 | #include <unistd.h> |
41669317 | 10 | |
971ff8c7 | 11 | #include "base-filesystem.h" |
3ffd4af2 | 12 | #include "fd-util.h" |
e5b42203 | 13 | #include "fs-util.h" |
a8fbdf54 | 14 | #include "log.h" |
f5947a5e | 15 | #include "missing_syscall.h" |
07630cea | 16 | #include "mkdir.h" |
e5b42203 | 17 | #include "mount-util.h" |
049af8ad | 18 | #include "mountpoint-util.h" |
07630cea LP |
19 | #include "path-util.h" |
20 | #include "rm-rf.h" | |
d054f0a4 | 21 | #include "stdio-util.h" |
07630cea | 22 | #include "string-util.h" |
e5b42203 | 23 | #include "strv.h" |
c6878637 | 24 | #include "switch-root.h" |
ee104e11 | 25 | #include "user-util.h" |
3ffd4af2 | 26 | #include "util.h" |
41669317 | 27 | |
e5b42203 LP |
28 | int switch_root(const char *new_root, |
29 | const char *old_root_after, /* path below the new root, where to place the old root after the transition */ | |
30 | bool unmount_old_root, | |
31 | unsigned long mount_flags) { /* MS_MOVE or MS_BIND */ | |
41669317 | 32 | |
e5b42203 | 33 | _cleanup_free_ char *resolved_old_root_after = NULL; |
03e334a1 | 34 | _cleanup_close_ int old_root_fd = -1; |
41669317 | 35 | bool old_root_remove; |
e5b42203 LP |
36 | const char *i; |
37 | int r; | |
38 | ||
39 | assert(new_root); | |
40 | assert(old_root_after); | |
41669317 LP |
41 | |
42 | if (path_equal(new_root, "/")) | |
43 | return 0; | |
44 | ||
e5b42203 | 45 | /* Check if we shall remove the contents of the old root */ |
41669317 | 46 | old_root_remove = in_initrd(); |
e5b42203 LP |
47 | if (old_root_remove) { |
48 | old_root_fd = open("/", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_NOCTTY|O_DIRECTORY); | |
49 | if (old_root_fd < 0) | |
50 | return log_error_errno(errno, "Failed to open root directory: %m"); | |
51 | } | |
41669317 | 52 | |
e5b42203 | 53 | /* Determine where we shall place the old root after the transition */ |
a5648b80 | 54 | r = chase_symlinks(old_root_after, new_root, CHASE_PREFIX_ROOT|CHASE_NONEXISTENT, &resolved_old_root_after, NULL); |
e5b42203 LP |
55 | if (r < 0) |
56 | return log_error_errno(r, "Failed to resolve %s/%s: %m", new_root, old_root_after); | |
57 | if (r == 0) /* Doesn't exist yet. Let's create it */ | |
58 | (void) mkdir_p_label(resolved_old_root_after, 0755); | |
41669317 | 59 | |
e5b42203 | 60 | /* Work-around for kernel design: the kernel refuses MS_MOVE if any file systems are mounted MS_SHARED. Hence |
d677d4df | 61 | * remount them MS_PRIVATE here as a work-around. |
f47fc355 LP |
62 | * |
63 | * https://bugzilla.redhat.com/show_bug.cgi?id=847418 */ | |
64 | if (mount(NULL, "/", NULL, MS_REC|MS_PRIVATE, NULL) < 0) | |
e5b42203 LP |
65 | return log_error_errno(errno, "Failed to set \"/\" mount propagation to private: %m"); |
66 | ||
67 | FOREACH_STRING(i, "/sys", "/dev", "/run", "/proc") { | |
68 | _cleanup_free_ char *chased = NULL; | |
69 | ||
a5648b80 | 70 | r = chase_symlinks(i, new_root, CHASE_PREFIX_ROOT|CHASE_NONEXISTENT, &chased, NULL); |
e5b42203 LP |
71 | if (r < 0) |
72 | return log_error_errno(r, "Failed to resolve %s/%s: %m", new_root, i); | |
73 | if (r > 0) { | |
74 | /* Already exists. Let's see if it is a mount point already. */ | |
75 | r = path_is_mount_point(chased, NULL, 0); | |
76 | if (r < 0) | |
77 | return log_error_errno(r, "Failed to determine whether %s is a mount point: %m", chased); | |
78 | if (r > 0) /* If it is already mounted, then do nothing */ | |
79 | continue; | |
80 | } else | |
81 | /* Doesn't exist yet? */ | |
82 | (void) mkdir_p_label(chased, 0755); | |
83 | ||
84 | if (mount(i, chased, NULL, mount_flags, NULL) < 0) | |
a5c67ccc | 85 | return log_error_errno(errno, "Failed to mount %s to %s: %m", i, chased); |
41669317 LP |
86 | } |
87 | ||
e5b42203 LP |
88 | /* Do not fail if base_filesystem_create() fails. Not all switch roots are like base_filesystem_create() wants |
89 | * them to look like. They might even boot, if they are RO and don't have the FS layout. Just ignore the error | |
90 | * and switch_root() nevertheless. */ | |
03cfe0d5 | 91 | (void) base_filesystem_create(new_root, UID_INVALID, GID_INVALID); |
971ff8c7 | 92 | |
4a62c710 MS |
93 | if (chdir(new_root) < 0) |
94 | return log_error_errno(errno, "Failed to change directory to %s: %m", new_root); | |
41669317 | 95 | |
e5b42203 LP |
96 | /* We first try a pivot_root() so that we can umount the old root dir. In many cases (i.e. where rootfs is /), |
97 | * that's not possible however, and hence we simply overmount root */ | |
98 | if (pivot_root(new_root, resolved_old_root_after) >= 0) { | |
891a4918 | 99 | |
5a4bf02f HH |
100 | /* Immediately get rid of the old root, if detach_oldroot is set. |
101 | * Since we are running off it we need to do this lazily. */ | |
e5b42203 LP |
102 | if (unmount_old_root) { |
103 | r = umount_recursive(old_root_after, MNT_DETACH); | |
104 | if (r < 0) | |
105 | log_warning_errno(r, "Failed to unmount old root directory tree, ignoring: %m"); | |
106 | } | |
891a4918 | 107 | |
4a62c710 | 108 | } else if (mount(new_root, "/", NULL, MS_MOVE, NULL) < 0) |
e5b42203 | 109 | return log_error_errno(errno, "Failed to move %s to /: %m", new_root); |
41669317 | 110 | |
4a62c710 MS |
111 | if (chroot(".") < 0) |
112 | return log_error_errno(errno, "Failed to change root: %m"); | |
41669317 | 113 | |
4a62c710 MS |
114 | if (chdir("/") < 0) |
115 | return log_error_errno(errno, "Failed to change directory: %m"); | |
ac0930c8 | 116 | |
41669317 LP |
117 | if (old_root_fd >= 0) { |
118 | struct stat rb; | |
119 | ||
120 | if (fstat(old_root_fd, &rb) < 0) | |
56f64d95 | 121 | log_warning_errno(errno, "Failed to stat old root directory, leaving: %m"); |
c0ba6b92 LP |
122 | else |
123 | (void) rm_rf_children(TAKE_FD(old_root_fd), 0, &rb); /* takes possession of the dir fd, even on failure */ | |
41669317 LP |
124 | } |
125 | ||
03e334a1 | 126 | return 0; |
41669317 | 127 | } |