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switch-root: check if old and new root fs is same via files_same_at()

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This commit is contained in:
Lennart Poettering 2023-05-16 14:57:20 +02:00
parent 676ade310a
commit 5268188de1
1 changed files with 12 additions and 7 deletions
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19
src/shared/switch-root.c
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@ -36,24 +36,29 @@ int switch_root(const char *new_root,
assert(new_root);
assert(IN_SET(mount_flags, MS_MOVE, MS_BIND));
if (path_equal(new_root, "/"))
return 0;
/* Check if we shall remove the contents of the old root */
old_root_fd = open("/", O_DIRECTORY|O_CLOEXEC);
if (old_root_fd < 0)
return log_error_errno(errno, "Failed to open root directory: %m");
new_root_fd = open(new_root, O_DIRECTORY|O_CLOEXEC);
if (new_root_fd < 0)
return log_error_errno(errno, "Failed to open target directory '%s': %m", new_root);
r = files_same_at(old_root_fd, "", new_root_fd, "", AT_EMPTY_PATH);
if (r < 0)
return log_error_errno(r, "Failed to determine if old and new root directory are the same: %m");
if (r > 0) {
log_debug("Skipping switch root, as old and new root directory are the same.");
return 0;
}
istmp = fd_is_temporary_fs(old_root_fd);
if (istmp < 0)
return log_error_errno(istmp, "Failed to stat root directory: %m");
if (istmp > 0)
log_debug("Root directory is on tmpfs, will do cleanup later.");
new_root_fd = open(new_root, O_DIRECTORY|O_CLOEXEC);
if (new_root_fd < 0)
return log_error_errno(errno, "Failed to open target directory '%s': %m", new_root);
if (old_root_after) {
/* Determine where we shall place the old root after the transition */
r = chase(old_root_after, new_root, CHASE_PREFIX_ROOT|CHASE_NONEXISTENT, &resolved_old_root_after, NULL);