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Commit | Line | Data |
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db9ecf05 | 1 | /* SPDX-License-Identifier: LGPL-2.1-or-later */ |
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" |
f4351959 | 12 | #include "chase-symlinks.h" |
3ffd4af2 | 13 | #include "fd-util.h" |
baa6a42d | 14 | #include "initrd-util.h" |
a8fbdf54 | 15 | #include "log.h" |
f5947a5e | 16 | #include "missing_syscall.h" |
35cd0ba5 | 17 | #include "mkdir-label.h" |
e5b42203 | 18 | #include "mount-util.h" |
049af8ad | 19 | #include "mountpoint-util.h" |
07630cea LP |
20 | #include "path-util.h" |
21 | #include "rm-rf.h" | |
d054f0a4 | 22 | #include "stdio-util.h" |
07630cea | 23 | #include "string-util.h" |
e5b42203 | 24 | #include "strv.h" |
c6878637 | 25 | #include "switch-root.h" |
ee104e11 | 26 | #include "user-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; |
254d1313 | 34 | _cleanup_close_ int old_root_fd = -EBADF; |
e5b42203 LP |
35 | int r; |
36 | ||
37 | assert(new_root); | |
38 | assert(old_root_after); | |
41669317 LP |
39 | |
40 | if (path_equal(new_root, "/")) | |
41 | return 0; | |
42 | ||
e5b42203 | 43 | /* Check if we shall remove the contents of the old root */ |
a940f507 ZJS |
44 | old_root_fd = open("/", O_RDONLY | O_CLOEXEC | O_DIRECTORY); |
45 | if (old_root_fd < 0) | |
46 | return log_error_errno(errno, "Failed to open root directory: %m"); | |
47 | r = fd_is_temporary_fs(old_root_fd); | |
48 | if (r < 0) | |
49 | return log_error_errno(r, "Failed to stat root directory: %m"); | |
50 | if (r > 0) | |
51 | log_debug("Root directory is on tmpfs, will do cleanup later."); | |
52 | else | |
53 | old_root_fd = safe_close(old_root_fd); | |
41669317 | 54 | |
e5b42203 | 55 | /* Determine where we shall place the old root after the transition */ |
a5648b80 | 56 | r = chase_symlinks(old_root_after, new_root, CHASE_PREFIX_ROOT|CHASE_NONEXISTENT, &resolved_old_root_after, NULL); |
e5b42203 LP |
57 | if (r < 0) |
58 | return log_error_errno(r, "Failed to resolve %s/%s: %m", new_root, old_root_after); | |
59 | if (r == 0) /* Doesn't exist yet. Let's create it */ | |
60 | (void) mkdir_p_label(resolved_old_root_after, 0755); | |
41669317 | 61 | |
e5b42203 | 62 | /* Work-around for kernel design: the kernel refuses MS_MOVE if any file systems are mounted MS_SHARED. Hence |
d677d4df | 63 | * remount them MS_PRIVATE here as a work-around. |
f47fc355 LP |
64 | * |
65 | * https://bugzilla.redhat.com/show_bug.cgi?id=847418 */ | |
66 | if (mount(NULL, "/", NULL, MS_REC|MS_PRIVATE, NULL) < 0) | |
e5b42203 LP |
67 | return log_error_errno(errno, "Failed to set \"/\" mount propagation to private: %m"); |
68 | ||
5980d463 | 69 | FOREACH_STRING(path, "/sys", "/dev", "/run", "/proc") { |
e5b42203 LP |
70 | _cleanup_free_ char *chased = NULL; |
71 | ||
5980d463 | 72 | r = chase_symlinks(path, new_root, CHASE_PREFIX_ROOT|CHASE_NONEXISTENT, &chased, NULL); |
e5b42203 | 73 | if (r < 0) |
5980d463 | 74 | return log_error_errno(r, "Failed to resolve %s/%s: %m", new_root, path); |
e5b42203 LP |
75 | if (r > 0) { |
76 | /* Already exists. Let's see if it is a mount point already. */ | |
77 | r = path_is_mount_point(chased, NULL, 0); | |
78 | if (r < 0) | |
79 | return log_error_errno(r, "Failed to determine whether %s is a mount point: %m", chased); | |
80 | if (r > 0) /* If it is already mounted, then do nothing */ | |
81 | continue; | |
82 | } else | |
83 | /* Doesn't exist yet? */ | |
84 | (void) mkdir_p_label(chased, 0755); | |
85 | ||
5980d463 ZJS |
86 | if (mount(path, chased, NULL, mount_flags, NULL) < 0) |
87 | return log_error_errno(errno, "Failed to mount %s to %s: %m", path, chased); | |
41669317 LP |
88 | } |
89 | ||
e5b42203 LP |
90 | /* Do not fail if base_filesystem_create() fails. Not all switch roots are like base_filesystem_create() wants |
91 | * them to look like. They might even boot, if they are RO and don't have the FS layout. Just ignore the error | |
92 | * and switch_root() nevertheless. */ | |
03cfe0d5 | 93 | (void) base_filesystem_create(new_root, UID_INVALID, GID_INVALID); |
971ff8c7 | 94 | |
4a62c710 MS |
95 | if (chdir(new_root) < 0) |
96 | return log_error_errno(errno, "Failed to change directory to %s: %m", new_root); | |
41669317 | 97 | |
e5b42203 LP |
98 | /* We first try a pivot_root() so that we can umount the old root dir. In many cases (i.e. where rootfs is /), |
99 | * that's not possible however, and hence we simply overmount root */ | |
100 | if (pivot_root(new_root, resolved_old_root_after) >= 0) { | |
891a4918 | 101 | |
5a4bf02f HH |
102 | /* Immediately get rid of the old root, if detach_oldroot is set. |
103 | * Since we are running off it we need to do this lazily. */ | |
e5b42203 LP |
104 | if (unmount_old_root) { |
105 | r = umount_recursive(old_root_after, MNT_DETACH); | |
106 | if (r < 0) | |
107 | log_warning_errno(r, "Failed to unmount old root directory tree, ignoring: %m"); | |
108 | } | |
891a4918 | 109 | |
4a62c710 | 110 | } else if (mount(new_root, "/", NULL, MS_MOVE, NULL) < 0) |
e5b42203 | 111 | return log_error_errno(errno, "Failed to move %s to /: %m", new_root); |
41669317 | 112 | |
4a62c710 MS |
113 | if (chroot(".") < 0) |
114 | return log_error_errno(errno, "Failed to change root: %m"); | |
41669317 | 115 | |
4a62c710 MS |
116 | if (chdir("/") < 0) |
117 | return log_error_errno(errno, "Failed to change directory: %m"); | |
ac0930c8 | 118 | |
41669317 LP |
119 | if (old_root_fd >= 0) { |
120 | struct stat rb; | |
121 | ||
122 | if (fstat(old_root_fd, &rb) < 0) | |
a940f507 ZJS |
123 | return log_error_errno(errno, "Failed to stat old root directory: %m"); |
124 | (void) rm_rf_children(TAKE_FD(old_root_fd), 0, &rb); /* takes possession of the dir fd, even on failure */ | |
41669317 LP |
125 | } |
126 | ||
03e334a1 | 127 | return 0; |
41669317 | 128 | } |