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Merge fc99d4b5db58de2b663e05c8bfc35c9a187a3bc4 into 6e1b24820fb6eae83cb8935867d4ef846cc36428

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Nick Rosbrook 2025-01-17 11:12:24 +01:00 committed by GitHub
commit ff11eeac3e
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1 changed files with 46 additions and 13 deletions
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59
src/shared/switch-root.c
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@ -37,14 +37,14 @@ int switch_root(const char *new_root,
static const struct {
const char *path;
unsigned long mount_flags; /* Flags to apply if SWITCH_ROOT_RECURSIVE_RUN is unset */
unsigned long mount_flags_recursive_run; /* Flags to apply if SWITCH_ROOT_RECURSIVE_RUN is set (0 if shall be skipped) */
bool skip_recursive_run; /* Whether or not this path should be skipped when SWITCH_ROOT_RECURSIVE_RUN is set */
} transfer_table[] = {
{ "/dev", MS_BIND|MS_REC, MS_BIND|MS_REC }, /* Recursive, because we want to save the original /dev/shm/ + /dev/pts/ and similar */
{ "/sys", MS_BIND|MS_REC, MS_BIND|MS_REC }, /* Similar, we want to retain various API VFS, or the cgroupv1 /sys/fs/cgroup/ tree */
{ "/proc", MS_BIND|MS_REC, MS_BIND|MS_REC }, /* Similar */
{ "/run", MS_BIND, MS_BIND|MS_REC }, /* Recursive except on soft reboot, see above */
{ "/run/credentials", MS_BIND|MS_REC, 0 /* skip! */ }, /* Credential mounts should survive */
{ "/run/host", MS_BIND|MS_REC, 0 /* skip! */ }, /* Host supplied hierarchy should also survive */
{ "/dev", MS_BIND|MS_REC, /* skip_recursive_run = */ false }, /* Recursive, because we want to save the original /dev/shm/ + /dev/pts/ and similar */
{ "/sys", MS_BIND|MS_REC, /* skip_recursive_run = */ false }, /* Similar, we want to retain various API VFS, or the cgroupv1 /sys/fs/cgroup/ tree */
{ "/proc", MS_BIND|MS_REC, /* skip_recursive_run = */ false }, /* Similar */
{ "/run", MS_BIND, /* skip_recursive_run = */ false }, /* Recursive except on soft reboot, see above */
{ "/run/credentials", MS_BIND|MS_REC, /* skip_recursive_run = */ true }, /* Credential mounts should survive */
{ "/run/host", MS_BIND|MS_REC, /* skip_recursive_run = */ true }, /* Host supplied hierarchy should also survive */
};
_cleanup_close_ int old_root_fd = -EBADF, new_root_fd = -EBADF;
@ -127,10 +127,8 @@ int switch_root(const char *new_root,
FOREACH_ELEMENT(transfer, transfer_table) {
_cleanup_free_ char *chased = NULL;
unsigned long mount_flags;
mount_flags = FLAGS_SET(flags, SWITCH_ROOT_RECURSIVE_RUN) ? transfer->mount_flags_recursive_run : transfer->mount_flags;
if (mount_flags == 0) /* skip if zero */
if (FLAGS_SET(flags, SWITCH_ROOT_RECURSIVE_RUN) && transfer->skip_recursive_run)
continue;
if (access(transfer->path, F_OK) < 0) {
@ -149,9 +147,44 @@ int switch_root(const char *new_root,
if (r > 0) /* If it is already mounted, then do nothing */
continue;
r = mount_nofollow_verbose(LOG_ERR, transfer->path, chased, NULL, mount_flags, NULL);
if (r < 0)
return r;
if (FLAGS_SET(flags, SWITCH_ROOT_RECURSIVE_RUN)) {
/* On recursive runs, first create a bind mount with MOVE_MOUNT_BENEATH, and then MS_MOVE
* the original mount point to the new root. This ensures that the mount point in the final
* destination is the original mount, but also ensures that the mount is available in the old
* root during the switch root. The latter is true because when we MS_MOVE, the bind mount is revelead. */
_cleanup_close_ int mnt_fd = -EBADF, target_fd = -EBADF;
target_fd = open(transfer->path, O_PATH|O_NOFOLLOW|O_CLOEXEC);
if (target_fd < 0)
return log_error_errno(errno, "Failed to open '%s': %m", transfer->path);
mnt_fd = open_tree(-EBADF, transfer->path, OPEN_TREE_CLONE|OPEN_TREE_CLOEXEC);
if (mnt_fd < 0)
return log_error_errno(errno, "Failed to open_tree '%s': %m", transfer->path);
r = RET_NERRNO(mount_setattr(mnt_fd, "", AT_EMPTY_PATH,
&(struct mount_attr) { .propagation = 0 },
MOUNT_ATTR_SIZE_VER0));
if (r < 0)
return log_error_errno(r, "Failed to set mount attrs: %m");
r = RET_NERRNO(move_mount(mnt_fd, "",
target_fd, "",
MOVE_MOUNT_BENEATH|MOVE_MOUNT_F_EMPTY_PATH|MOVE_MOUNT_T_EMPTY_PATH));
if (r == -EINVAL)
log_warning_errno(r, "Failed to move bind mount beneath '%s', ignoring: %m", transfer->path);
else if (r < 0)
return log_debug_errno(r, "Failed to move bind mount beneath '%s': %m", transfer->path);
r = mount_nofollow_verbose(LOG_ERR, transfer->path, chased, NULL, MS_MOVE, NULL);
if (r < 0)
return r;
} else {
r = mount_nofollow_verbose(LOG_ERR, transfer->path, chased, NULL, transfer->mount_flags, NULL);
if (r < 0)
return r;
}
}
if (fchdir(new_root_fd) < 0)