11a1589223
Files which are installed as-is (any .service and other unit files, .conf files, .policy files, etc), are left as is. My assumption is that SPDX identifiers are not yet that well known, so it's better to retain the extended header to avoid any doubt. I also kept any copyright lines. We can probably remove them, but it'd nice to obtain explicit acks from all involved authors before doing that.
135 lines
5.4 KiB
C
135 lines
5.4 KiB
C
/* SPDX-License-Identifier: LGPL-2.1+ */
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/***
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This file is part of systemd.
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Copyright 2012 Harald Hoyer, Lennart Poettering
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***/
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#include <errno.h>
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#include <fcntl.h>
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#include <limits.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <sys/mount.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include "base-filesystem.h"
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#include "fd-util.h"
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#include "fs-util.h"
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#include "log.h"
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#include "missing.h"
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#include "mkdir.h"
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#include "mount-util.h"
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#include "path-util.h"
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#include "rm-rf.h"
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#include "stdio-util.h"
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#include "string-util.h"
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#include "strv.h"
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#include "switch-root.h"
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#include "user-util.h"
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#include "util.h"
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int switch_root(const char *new_root,
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const char *old_root_after, /* path below the new root, where to place the old root after the transition */
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bool unmount_old_root,
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unsigned long mount_flags) { /* MS_MOVE or MS_BIND */
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_cleanup_free_ char *resolved_old_root_after = NULL;
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_cleanup_close_ int old_root_fd = -1;
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bool old_root_remove;
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const char *i;
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int r;
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assert(new_root);
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assert(old_root_after);
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if (path_equal(new_root, "/"))
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return 0;
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/* Check if we shall remove the contents of the old root */
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old_root_remove = in_initrd();
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if (old_root_remove) {
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old_root_fd = open("/", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_NOCTTY|O_DIRECTORY);
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if (old_root_fd < 0)
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return log_error_errno(errno, "Failed to open root directory: %m");
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}
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/* Determine where we shall place the old root after the transition */
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r = chase_symlinks(old_root_after, new_root, CHASE_PREFIX_ROOT|CHASE_NONEXISTENT, &resolved_old_root_after);
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if (r < 0)
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return log_error_errno(r, "Failed to resolve %s/%s: %m", new_root, old_root_after);
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if (r == 0) /* Doesn't exist yet. Let's create it */
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(void) mkdir_p_label(resolved_old_root_after, 0755);
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/* Work-around for kernel design: the kernel refuses MS_MOVE if any file systems are mounted MS_SHARED. Hence
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* remount them MS_PRIVATE here as a work-around.
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*
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* https://bugzilla.redhat.com/show_bug.cgi?id=847418 */
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if (mount(NULL, "/", NULL, MS_REC|MS_PRIVATE, NULL) < 0)
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return log_error_errno(errno, "Failed to set \"/\" mount propagation to private: %m");
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FOREACH_STRING(i, "/sys", "/dev", "/run", "/proc") {
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_cleanup_free_ char *chased = NULL;
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r = chase_symlinks(i, new_root, CHASE_PREFIX_ROOT|CHASE_NONEXISTENT, &chased);
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if (r < 0)
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return log_error_errno(r, "Failed to resolve %s/%s: %m", new_root, i);
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if (r > 0) {
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/* Already exists. Let's see if it is a mount point already. */
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r = path_is_mount_point(chased, NULL, 0);
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if (r < 0)
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return log_error_errno(r, "Failed to determine whether %s is a mount point: %m", chased);
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if (r > 0) /* If it is already mounted, then do nothing */
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continue;
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} else
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/* Doesn't exist yet? */
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(void) mkdir_p_label(chased, 0755);
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if (mount(i, chased, NULL, mount_flags, NULL) < 0)
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return log_error_errno(r, "Failed to mount %s to %s: %m", i, chased);
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}
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/* Do not fail if base_filesystem_create() fails. Not all switch roots are like base_filesystem_create() wants
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* them to look like. They might even boot, if they are RO and don't have the FS layout. Just ignore the error
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* and switch_root() nevertheless. */
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(void) base_filesystem_create(new_root, UID_INVALID, GID_INVALID);
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if (chdir(new_root) < 0)
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return log_error_errno(errno, "Failed to change directory to %s: %m", new_root);
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/* We first try a pivot_root() so that we can umount the old root dir. In many cases (i.e. where rootfs is /),
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* that's not possible however, and hence we simply overmount root */
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if (pivot_root(new_root, resolved_old_root_after) >= 0) {
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/* Immediately get rid of the old root, if detach_oldroot is set.
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* Since we are running off it we need to do this lazily. */
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if (unmount_old_root) {
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r = umount_recursive(old_root_after, MNT_DETACH);
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if (r < 0)
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log_warning_errno(r, "Failed to unmount old root directory tree, ignoring: %m");
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}
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} else if (mount(new_root, "/", NULL, MS_MOVE, NULL) < 0)
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return log_error_errno(errno, "Failed to move %s to /: %m", new_root);
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if (chroot(".") < 0)
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return log_error_errno(errno, "Failed to change root: %m");
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if (chdir("/") < 0)
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return log_error_errno(errno, "Failed to change directory: %m");
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if (old_root_fd >= 0) {
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struct stat rb;
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if (fstat(old_root_fd, &rb) < 0)
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log_warning_errno(errno, "Failed to stat old root directory, leaving: %m");
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else {
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(void) rm_rf_children(old_root_fd, 0, &rb);
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old_root_fd = -1;
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}
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}
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return 0;
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}
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