mirror of
https://github.com/morgan9e/systemd
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254d1313ae
-1 was used everywhere, but -EBADF or -EBADFD started being used in various places. Let's make things consistent in the new style. Note that there are two candidates: EBADF 9 Bad file descriptor EBADFD 77 File descriptor in bad state Since we're initializating the fd, we're just assigning a value that means "no fd yet", so it's just a bad file descriptor, and the first errno fits better. If instead we had a valid file descriptor that became invalid because of some operation or state change, the other errno would fit better. In some places, initialization is dropped if unnecessary.
129 lines
5.5 KiB
C
129 lines
5.5 KiB
C
/* SPDX-License-Identifier: LGPL-2.1-or-later */
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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 <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 "chase-symlinks.h"
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#include "fd-util.h"
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#include "initrd-util.h"
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#include "log.h"
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#include "missing_syscall.h"
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#include "mkdir-label.h"
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#include "mount-util.h"
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#include "mountpoint-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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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 = -EBADF;
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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_fd = open("/", O_RDONLY | O_CLOEXEC | 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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r = fd_is_temporary_fs(old_root_fd);
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if (r < 0)
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return log_error_errno(r, "Failed to stat root directory: %m");
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if (r > 0)
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log_debug("Root directory is on tmpfs, will do cleanup later.");
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else
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old_root_fd = safe_close(old_root_fd);
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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, NULL);
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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(path, "/sys", "/dev", "/run", "/proc") {
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_cleanup_free_ char *chased = NULL;
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r = chase_symlinks(path, new_root, CHASE_PREFIX_ROOT|CHASE_NONEXISTENT, &chased, NULL);
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if (r < 0)
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return log_error_errno(r, "Failed to resolve %s/%s: %m", new_root, path);
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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(path, chased, NULL, mount_flags, NULL) < 0)
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return log_error_errno(errno, "Failed to mount %s to %s: %m", path, 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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return log_error_errno(errno, "Failed to stat old root directory: %m");
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(void) rm_rf_children(TAKE_FD(old_root_fd), 0, &rb); /* takes possession of the dir fd, even on failure */
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}
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return 0;
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}
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