1006 lines
33 KiB
C
1006 lines
33 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 2010 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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#include <errno.h>
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#include <stddef.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/stat.h>
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#include <linux/magic.h>
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#include <time.h>
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#include <unistd.h>
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#include "alloc-util.h"
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#include "dirent-util.h"
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#include "fd-util.h"
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#include "fileio.h"
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#include "fs-util.h"
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#include "log.h"
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#include "macro.h"
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#include "missing.h"
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#include "mkdir.h"
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#include "parse-util.h"
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#include "path-util.h"
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#include "process-util.h"
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#include "stat-util.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 "time-util.h"
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#include "user-util.h"
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#include "util.h"
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int unlink_noerrno(const char *path) {
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PROTECT_ERRNO;
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int r;
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r = unlink(path);
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if (r < 0)
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return -errno;
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return 0;
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}
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int rmdir_parents(const char *path, const char *stop) {
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size_t l;
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int r = 0;
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assert(path);
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assert(stop);
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l = strlen(path);
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/* Skip trailing slashes */
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while (l > 0 && path[l-1] == '/')
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l--;
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while (l > 0) {
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char *t;
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/* Skip last component */
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while (l > 0 && path[l-1] != '/')
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l--;
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/* Skip trailing slashes */
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while (l > 0 && path[l-1] == '/')
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l--;
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if (l <= 0)
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break;
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t = strndup(path, l);
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if (!t)
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return -ENOMEM;
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if (path_startswith(stop, t)) {
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free(t);
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return 0;
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}
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r = rmdir(t);
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free(t);
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if (r < 0)
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if (errno != ENOENT)
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return -errno;
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}
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return 0;
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}
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int rename_noreplace(int olddirfd, const char *oldpath, int newdirfd, const char *newpath) {
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struct stat buf;
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int ret;
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ret = renameat2(olddirfd, oldpath, newdirfd, newpath, RENAME_NOREPLACE);
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if (ret >= 0)
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return 0;
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/* renameat2() exists since Linux 3.15, btrfs added support for it later.
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* If it is not implemented, fallback to another method. */
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if (!IN_SET(errno, EINVAL, ENOSYS))
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return -errno;
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/* The link()/unlink() fallback does not work on directories. But
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* renameat() without RENAME_NOREPLACE gives the same semantics on
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* directories, except when newpath is an *empty* directory. This is
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* good enough. */
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ret = fstatat(olddirfd, oldpath, &buf, AT_SYMLINK_NOFOLLOW);
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if (ret >= 0 && S_ISDIR(buf.st_mode)) {
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ret = renameat(olddirfd, oldpath, newdirfd, newpath);
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return ret >= 0 ? 0 : -errno;
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}
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/* If it is not a directory, use the link()/unlink() fallback. */
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ret = linkat(olddirfd, oldpath, newdirfd, newpath, 0);
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if (ret < 0)
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return -errno;
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ret = unlinkat(olddirfd, oldpath, 0);
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if (ret < 0) {
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/* backup errno before the following unlinkat() alters it */
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ret = errno;
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(void) unlinkat(newdirfd, newpath, 0);
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errno = ret;
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return -errno;
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}
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return 0;
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}
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int readlinkat_malloc(int fd, const char *p, char **ret) {
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size_t l = 100;
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int r;
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assert(p);
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assert(ret);
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for (;;) {
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char *c;
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ssize_t n;
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c = new(char, l);
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if (!c)
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return -ENOMEM;
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n = readlinkat(fd, p, c, l-1);
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if (n < 0) {
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r = -errno;
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free(c);
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return r;
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}
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if ((size_t) n < l-1) {
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c[n] = 0;
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*ret = c;
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return 0;
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}
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free(c);
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l *= 2;
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}
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}
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int readlink_malloc(const char *p, char **ret) {
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return readlinkat_malloc(AT_FDCWD, p, ret);
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}
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int readlink_value(const char *p, char **ret) {
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_cleanup_free_ char *link = NULL;
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char *value;
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int r;
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r = readlink_malloc(p, &link);
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if (r < 0)
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return r;
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value = basename(link);
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if (!value)
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return -ENOENT;
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value = strdup(value);
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if (!value)
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return -ENOMEM;
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*ret = value;
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return 0;
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}
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int readlink_and_make_absolute(const char *p, char **r) {
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_cleanup_free_ char *target = NULL;
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char *k;
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int j;
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assert(p);
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assert(r);
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j = readlink_malloc(p, &target);
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if (j < 0)
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return j;
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k = file_in_same_dir(p, target);
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if (!k)
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return -ENOMEM;
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*r = k;
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return 0;
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}
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int chmod_and_chown(const char *path, mode_t mode, uid_t uid, gid_t gid) {
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assert(path);
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/* Under the assumption that we are running privileged we
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* first change the access mode and only then hand out
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* ownership to avoid a window where access is too open. */
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if (mode != MODE_INVALID)
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if (chmod(path, mode) < 0)
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return -errno;
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if (uid != UID_INVALID || gid != GID_INVALID)
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if (chown(path, uid, gid) < 0)
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return -errno;
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return 0;
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}
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int fchmod_umask(int fd, mode_t m) {
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mode_t u;
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int r;
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u = umask(0777);
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r = fchmod(fd, m & (~u)) < 0 ? -errno : 0;
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umask(u);
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return r;
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}
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int fd_warn_permissions(const char *path, int fd) {
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struct stat st;
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if (fstat(fd, &st) < 0)
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return -errno;
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if (st.st_mode & 0111)
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log_warning("Configuration file %s is marked executable. Please remove executable permission bits. Proceeding anyway.", path);
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if (st.st_mode & 0002)
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log_warning("Configuration file %s is marked world-writable. Please remove world writability permission bits. Proceeding anyway.", path);
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if (getpid_cached() == 1 && (st.st_mode & 0044) != 0044)
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log_warning("Configuration file %s is marked world-inaccessible. This has no effect as configuration data is accessible via APIs without restrictions. Proceeding anyway.", path);
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return 0;
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}
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int touch_file(const char *path, bool parents, usec_t stamp, uid_t uid, gid_t gid, mode_t mode) {
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char fdpath[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
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_cleanup_close_ int fd = -1;
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int r, ret = 0;
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assert(path);
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/* Note that touch_file() does not follow symlinks: if invoked on an existing symlink, then it is the symlink
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* itself which is updated, not its target
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*
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* Returns the first error we encounter, but tries to apply as much as possible. */
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if (parents)
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(void) mkdir_parents(path, 0755);
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/* Initially, we try to open the node with O_PATH, so that we get a reference to the node. This is useful in
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* case the path refers to an existing device or socket node, as we can open it successfully in all cases, and
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* won't trigger any driver magic or so. */
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fd = open(path, O_PATH|O_CLOEXEC|O_NOFOLLOW);
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if (fd < 0) {
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if (errno != ENOENT)
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return -errno;
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/* if the node doesn't exist yet, we create it, but with O_EXCL, so that we only create a regular file
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* here, and nothing else */
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fd = open(path, O_WRONLY|O_CREAT|O_EXCL|O_CLOEXEC, IN_SET(mode, 0, MODE_INVALID) ? 0644 : mode);
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if (fd < 0)
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return -errno;
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}
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/* Let's make a path from the fd, and operate on that. With this logic, we can adjust the access mode,
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* ownership and time of the file node in all cases, even if the fd refers to an O_PATH object — which is
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* something fchown(), fchmod(), futimensat() don't allow. */
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xsprintf(fdpath, "/proc/self/fd/%i", fd);
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if (mode != MODE_INVALID)
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if (chmod(fdpath, mode) < 0)
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ret = -errno;
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if (uid_is_valid(uid) || gid_is_valid(gid))
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if (chown(fdpath, uid, gid) < 0 && ret >= 0)
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ret = -errno;
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if (stamp != USEC_INFINITY) {
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struct timespec ts[2];
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timespec_store(&ts[0], stamp);
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ts[1] = ts[0];
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r = utimensat(AT_FDCWD, fdpath, ts, 0);
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} else
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r = utimensat(AT_FDCWD, fdpath, NULL, 0);
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if (r < 0 && ret >= 0)
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return -errno;
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return ret;
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}
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int touch(const char *path) {
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return touch_file(path, false, USEC_INFINITY, UID_INVALID, GID_INVALID, MODE_INVALID);
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}
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int symlink_idempotent(const char *from, const char *to) {
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int r;
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assert(from);
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assert(to);
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if (symlink(from, to) < 0) {
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_cleanup_free_ char *p = NULL;
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if (errno != EEXIST)
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return -errno;
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r = readlink_malloc(to, &p);
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if (r == -EINVAL) /* Not a symlink? In that case return the original error we encountered: -EEXIST */
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return -EEXIST;
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if (r < 0) /* Any other error? In that case propagate it as is */
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return r;
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if (!streq(p, from)) /* Not the symlink we want it to be? In that case, propagate the original -EEXIST */
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return -EEXIST;
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}
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return 0;
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}
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int symlink_atomic(const char *from, const char *to) {
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_cleanup_free_ char *t = NULL;
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int r;
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assert(from);
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assert(to);
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r = tempfn_random(to, NULL, &t);
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if (r < 0)
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return r;
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if (symlink(from, t) < 0)
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return -errno;
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if (rename(t, to) < 0) {
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unlink_noerrno(t);
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return -errno;
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}
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return 0;
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}
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int mknod_atomic(const char *path, mode_t mode, dev_t dev) {
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_cleanup_free_ char *t = NULL;
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int r;
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assert(path);
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r = tempfn_random(path, NULL, &t);
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if (r < 0)
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return r;
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if (mknod(t, mode, dev) < 0)
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return -errno;
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if (rename(t, path) < 0) {
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unlink_noerrno(t);
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return -errno;
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}
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return 0;
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}
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int mkfifo_atomic(const char *path, mode_t mode) {
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_cleanup_free_ char *t = NULL;
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int r;
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assert(path);
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r = tempfn_random(path, NULL, &t);
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if (r < 0)
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return r;
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if (mkfifo(t, mode) < 0)
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return -errno;
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if (rename(t, path) < 0) {
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unlink_noerrno(t);
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return -errno;
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}
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return 0;
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}
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int get_files_in_directory(const char *path, char ***list) {
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_cleanup_closedir_ DIR *d = NULL;
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struct dirent *de;
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size_t bufsize = 0, n = 0;
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_cleanup_strv_free_ char **l = NULL;
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assert(path);
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/* Returns all files in a directory in *list, and the number
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* of files as return value. If list is NULL returns only the
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* number. */
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d = opendir(path);
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if (!d)
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return -errno;
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FOREACH_DIRENT_ALL(de, d, return -errno) {
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dirent_ensure_type(d, de);
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if (!dirent_is_file(de))
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continue;
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if (list) {
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/* one extra slot is needed for the terminating NULL */
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if (!GREEDY_REALLOC(l, bufsize, n + 2))
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return -ENOMEM;
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l[n] = strdup(de->d_name);
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if (!l[n])
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return -ENOMEM;
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l[++n] = NULL;
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} else
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n++;
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}
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if (list)
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*list = TAKE_PTR(l);
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return n;
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}
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static int getenv_tmp_dir(const char **ret_path) {
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const char *n;
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int r, ret = 0;
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assert(ret_path);
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/* We use the same order of environment variables python uses in tempfile.gettempdir():
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* https://docs.python.org/3/library/tempfile.html#tempfile.gettempdir */
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FOREACH_STRING(n, "TMPDIR", "TEMP", "TMP") {
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const char *e;
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e = secure_getenv(n);
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if (!e)
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continue;
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if (!path_is_absolute(e)) {
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r = -ENOTDIR;
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goto next;
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}
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if (!path_is_normalized(e)) {
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r = -EPERM;
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goto next;
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}
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r = is_dir(e, true);
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if (r < 0)
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goto next;
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if (r == 0) {
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r = -ENOTDIR;
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goto next;
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}
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*ret_path = e;
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return 1;
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next:
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/* Remember first error, to make this more debuggable */
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if (ret >= 0)
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ret = r;
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}
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if (ret < 0)
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return ret;
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*ret_path = NULL;
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return ret;
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}
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static int tmp_dir_internal(const char *def, const char **ret) {
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const char *e;
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int r, k;
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assert(def);
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assert(ret);
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r = getenv_tmp_dir(&e);
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if (r > 0) {
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*ret = e;
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return 0;
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}
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k = is_dir(def, true);
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if (k == 0)
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k = -ENOTDIR;
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if (k < 0)
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return r < 0 ? r : k;
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*ret = def;
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return 0;
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}
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int var_tmp_dir(const char **ret) {
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/* Returns the location for "larger" temporary files, that is backed by physical storage if available, and thus
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* even might survive a boot: /var/tmp. If $TMPDIR (or related environment variables) are set, its value is
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* returned preferably however. Note that both this function and tmp_dir() below are affected by $TMPDIR,
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* making it a variable that overrides all temporary file storage locations. */
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return tmp_dir_internal("/var/tmp", ret);
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}
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int tmp_dir(const char **ret) {
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/* Similar to var_tmp_dir() above, but returns the location for "smaller" temporary files, which is usually
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* backed by an in-memory file system: /tmp. */
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return tmp_dir_internal("/tmp", ret);
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}
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int unlink_or_warn(const char *filename) {
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if (unlink(filename) < 0 && errno != ENOENT)
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/* If the file doesn't exist and the fs simply was read-only (in which
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* case unlink() returns EROFS even if the file doesn't exist), don't
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* complain */
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if (errno != EROFS || access(filename, F_OK) >= 0)
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return log_error_errno(errno, "Failed to remove \"%s\": %m", filename);
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return 0;
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}
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int inotify_add_watch_fd(int fd, int what, uint32_t mask) {
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||
char path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1];
|
||
int r;
|
||
|
||
/* This is like inotify_add_watch(), except that the file to watch is not referenced by a path, but by an fd */
|
||
xsprintf(path, "/proc/self/fd/%i", what);
|
||
|
||
r = inotify_add_watch(fd, path, mask);
|
||
if (r < 0)
|
||
return -errno;
|
||
|
||
return r;
|
||
}
|
||
|
||
static bool safe_transition(const struct stat *a, const struct stat *b) {
|
||
/* Returns true if the transition from a to b is safe, i.e. that we never transition from unprivileged to
|
||
* privileged files or directories. Why bother? So that unprivileged code can't symlink to privileged files
|
||
* making us believe we read something safe even though it isn't safe in the specific context we open it in. */
|
||
|
||
if (a->st_uid == 0) /* Transitioning from privileged to unprivileged is always fine */
|
||
return true;
|
||
|
||
return a->st_uid == b->st_uid; /* Otherwise we need to stay within the same UID */
|
||
}
|
||
|
||
int chase_symlinks(const char *path, const char *original_root, unsigned flags, char **ret) {
|
||
_cleanup_free_ char *buffer = NULL, *done = NULL, *root = NULL;
|
||
_cleanup_close_ int fd = -1;
|
||
unsigned max_follow = 32; /* how many symlinks to follow before giving up and returning ELOOP */
|
||
struct stat previous_stat;
|
||
bool exists = true;
|
||
char *todo;
|
||
int r;
|
||
|
||
assert(path);
|
||
|
||
/* Either the file may be missing, or we return an fd to the final object, but both make no sense */
|
||
if ((flags & (CHASE_NONEXISTENT|CHASE_OPEN)) == (CHASE_NONEXISTENT|CHASE_OPEN))
|
||
return -EINVAL;
|
||
|
||
if (isempty(path))
|
||
return -EINVAL;
|
||
|
||
/* This is a lot like canonicalize_file_name(), but takes an additional "root" parameter, that allows following
|
||
* symlinks relative to a root directory, instead of the root of the host.
|
||
*
|
||
* Note that "root" primarily matters if we encounter an absolute symlink. It is also used when following
|
||
* relative symlinks to ensure they cannot be used to "escape" the root directory. The path parameter passed is
|
||
* assumed to be already prefixed by it, except if the CHASE_PREFIX_ROOT flag is set, in which case it is first
|
||
* prefixed accordingly.
|
||
*
|
||
* Algorithmically this operates on two path buffers: "done" are the components of the path we already
|
||
* processed and resolved symlinks, "." and ".." of. "todo" are the components of the path we still need to
|
||
* process. On each iteration, we move one component from "todo" to "done", processing it's special meaning
|
||
* each time. The "todo" path always starts with at least one slash, the "done" path always ends in no
|
||
* slash. We always keep an O_PATH fd to the component we are currently processing, thus keeping lookup races
|
||
* at a minimum.
|
||
*
|
||
* Suggested usage: whenever you want to canonicalize a path, use this function. Pass the absolute path you got
|
||
* as-is: fully qualified and relative to your host's root. Optionally, specify the root parameter to tell this
|
||
* function what to do when encountering a symlink with an absolute path as directory: prefix it by the
|
||
* specified path. */
|
||
|
||
/* A root directory of "/" or "" is identical to none */
|
||
if (isempty(original_root) || path_equal(original_root, "/"))
|
||
original_root = NULL;
|
||
|
||
if (original_root) {
|
||
r = path_make_absolute_cwd(original_root, &root);
|
||
if (r < 0)
|
||
return r;
|
||
|
||
if (flags & CHASE_PREFIX_ROOT) {
|
||
|
||
/* We don't support relative paths in combination with a root directory */
|
||
if (!path_is_absolute(path))
|
||
return -EINVAL;
|
||
|
||
path = prefix_roota(root, path);
|
||
}
|
||
}
|
||
|
||
r = path_make_absolute_cwd(path, &buffer);
|
||
if (r < 0)
|
||
return r;
|
||
|
||
fd = open("/", O_CLOEXEC|O_NOFOLLOW|O_PATH);
|
||
if (fd < 0)
|
||
return -errno;
|
||
|
||
if (flags & CHASE_SAFE) {
|
||
if (fstat(fd, &previous_stat) < 0)
|
||
return -errno;
|
||
}
|
||
|
||
todo = buffer;
|
||
for (;;) {
|
||
_cleanup_free_ char *first = NULL;
|
||
_cleanup_close_ int child = -1;
|
||
struct stat st;
|
||
size_t n, m;
|
||
|
||
/* Determine length of first component in the path */
|
||
n = strspn(todo, "/"); /* The slashes */
|
||
m = n + strcspn(todo + n, "/"); /* The entire length of the component */
|
||
|
||
/* Extract the first component. */
|
||
first = strndup(todo, m);
|
||
if (!first)
|
||
return -ENOMEM;
|
||
|
||
todo += m;
|
||
|
||
/* Empty? Then we reached the end. */
|
||
if (isempty(first))
|
||
break;
|
||
|
||
/* Just a single slash? Then we reached the end. */
|
||
if (path_equal(first, "/")) {
|
||
/* Preserve the trailing slash */
|
||
if (!strextend(&done, "/", NULL))
|
||
return -ENOMEM;
|
||
|
||
break;
|
||
}
|
||
|
||
/* Just a dot? Then let's eat this up. */
|
||
if (path_equal(first, "/."))
|
||
continue;
|
||
|
||
/* Two dots? Then chop off the last bit of what we already found out. */
|
||
if (path_equal(first, "/..")) {
|
||
_cleanup_free_ char *parent = NULL;
|
||
_cleanup_close_ int fd_parent = -1;
|
||
|
||
/* If we already are at the top, then going up will not change anything. This is in-line with
|
||
* how the kernel handles this. */
|
||
if (isempty(done) || path_equal(done, "/"))
|
||
continue;
|
||
|
||
parent = dirname_malloc(done);
|
||
if (!parent)
|
||
return -ENOMEM;
|
||
|
||
/* Don't allow this to leave the root dir. */
|
||
if (root &&
|
||
path_startswith(done, root) &&
|
||
!path_startswith(parent, root))
|
||
continue;
|
||
|
||
free_and_replace(done, parent);
|
||
|
||
fd_parent = openat(fd, "..", O_CLOEXEC|O_NOFOLLOW|O_PATH);
|
||
if (fd_parent < 0)
|
||
return -errno;
|
||
|
||
if (flags & CHASE_SAFE) {
|
||
if (fstat(fd_parent, &st) < 0)
|
||
return -errno;
|
||
|
||
if (!safe_transition(&previous_stat, &st))
|
||
return -EPERM;
|
||
|
||
previous_stat = st;
|
||
}
|
||
|
||
safe_close(fd);
|
||
fd = fd_parent;
|
||
fd_parent = -1;
|
||
|
||
continue;
|
||
}
|
||
|
||
/* Otherwise let's see what this is. */
|
||
child = openat(fd, first + n, O_CLOEXEC|O_NOFOLLOW|O_PATH);
|
||
if (child < 0) {
|
||
|
||
if (errno == ENOENT &&
|
||
(flags & CHASE_NONEXISTENT) &&
|
||
(isempty(todo) || path_is_normalized(todo))) {
|
||
|
||
/* If CHASE_NONEXISTENT is set, and the path does not exist, then that's OK, return
|
||
* what we got so far. But don't allow this if the remaining path contains "../ or "./"
|
||
* or something else weird. */
|
||
|
||
/* If done is "/", as first also contains slash at the head, then remove this redundant slash. */
|
||
if (streq_ptr(done, "/"))
|
||
*done = '\0';
|
||
|
||
if (!strextend(&done, first, todo, NULL))
|
||
return -ENOMEM;
|
||
|
||
exists = false;
|
||
break;
|
||
}
|
||
|
||
return -errno;
|
||
}
|
||
|
||
if (fstat(child, &st) < 0)
|
||
return -errno;
|
||
if ((flags & CHASE_SAFE) &&
|
||
!safe_transition(&previous_stat, &st))
|
||
return -EPERM;
|
||
|
||
previous_stat = st;
|
||
|
||
if ((flags & CHASE_NO_AUTOFS) &&
|
||
fd_is_fs_type(child, AUTOFS_SUPER_MAGIC) > 0)
|
||
return -EREMOTE;
|
||
|
||
if (S_ISLNK(st.st_mode)) {
|
||
char *joined;
|
||
|
||
_cleanup_free_ char *destination = NULL;
|
||
|
||
/* This is a symlink, in this case read the destination. But let's make sure we don't follow
|
||
* symlinks without bounds. */
|
||
if (--max_follow <= 0)
|
||
return -ELOOP;
|
||
|
||
r = readlinkat_malloc(fd, first + n, &destination);
|
||
if (r < 0)
|
||
return r;
|
||
if (isempty(destination))
|
||
return -EINVAL;
|
||
|
||
if (path_is_absolute(destination)) {
|
||
|
||
/* An absolute destination. Start the loop from the beginning, but use the root
|
||
* directory as base. */
|
||
|
||
safe_close(fd);
|
||
fd = open(root ?: "/", O_CLOEXEC|O_NOFOLLOW|O_PATH);
|
||
if (fd < 0)
|
||
return -errno;
|
||
|
||
if (flags & CHASE_SAFE) {
|
||
if (fstat(fd, &st) < 0)
|
||
return -errno;
|
||
|
||
if (!safe_transition(&previous_stat, &st))
|
||
return -EPERM;
|
||
|
||
previous_stat = st;
|
||
}
|
||
|
||
free(done);
|
||
|
||
/* Note that we do not revalidate the root, we take it as is. */
|
||
if (isempty(root))
|
||
done = NULL;
|
||
else {
|
||
done = strdup(root);
|
||
if (!done)
|
||
return -ENOMEM;
|
||
}
|
||
|
||
/* Prefix what's left to do with what we just read, and start the loop again, but
|
||
* remain in the current directory. */
|
||
joined = strjoin(destination, todo);
|
||
} else
|
||
joined = strjoin("/", destination, todo);
|
||
if (!joined)
|
||
return -ENOMEM;
|
||
|
||
free(buffer);
|
||
todo = buffer = joined;
|
||
|
||
continue;
|
||
}
|
||
|
||
/* If this is not a symlink, then let's just add the name we read to what we already verified. */
|
||
if (!done)
|
||
done = TAKE_PTR(first);
|
||
else {
|
||
/* If done is "/", as first also contains slash at the head, then remove this redundant slash. */
|
||
if (streq(done, "/"))
|
||
*done = '\0';
|
||
|
||
if (!strextend(&done, first, NULL))
|
||
return -ENOMEM;
|
||
}
|
||
|
||
/* And iterate again, but go one directory further down. */
|
||
safe_close(fd);
|
||
fd = child;
|
||
child = -1;
|
||
}
|
||
|
||
if (!done) {
|
||
/* Special case, turn the empty string into "/", to indicate the root directory. */
|
||
done = strdup("/");
|
||
if (!done)
|
||
return -ENOMEM;
|
||
}
|
||
|
||
if (ret)
|
||
*ret = TAKE_PTR(done);
|
||
|
||
if (flags & CHASE_OPEN) {
|
||
int q;
|
||
|
||
/* Return the O_PATH fd we currently are looking to the caller. It can translate it to a proper fd by
|
||
* opening /proc/self/fd/xyz. */
|
||
|
||
assert(fd >= 0);
|
||
q = fd;
|
||
fd = -1;
|
||
|
||
return q;
|
||
}
|
||
|
||
return exists;
|
||
}
|
||
|
||
int access_fd(int fd, int mode) {
|
||
char p[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(fd) + 1];
|
||
int r;
|
||
|
||
/* Like access() but operates on an already open fd */
|
||
|
||
xsprintf(p, "/proc/self/fd/%i", fd);
|
||
|
||
r = access(p, mode);
|
||
if (r < 0)
|
||
r = -errno;
|
||
|
||
return r;
|
||
}
|
||
|
||
int unlinkat_deallocate(int fd, const char *name, int flags) {
|
||
_cleanup_close_ int truncate_fd = -1;
|
||
struct stat st;
|
||
off_t l, bs;
|
||
|
||
/* Operates like unlinkat() but also deallocates the file contents if it is a regular file and there's no other
|
||
* link to it. This is useful to ensure that other processes that might have the file open for reading won't be
|
||
* able to keep the data pinned on disk forever. This call is particular useful whenever we execute clean-up
|
||
* jobs ("vacuuming"), where we want to make sure the data is really gone and the disk space released and
|
||
* returned to the free pool.
|
||
*
|
||
* Deallocation is preferably done by FALLOC_FL_PUNCH_HOLE|FALLOC_FL_KEEP_SIZE (👊) if supported, which means
|
||
* the file won't change size. That's a good thing since we shouldn't needlessly trigger SIGBUS in other
|
||
* programs that have mmap()ed the file. (The assumption here is that changing file contents to all zeroes
|
||
* underneath those programs is the better choice than simply triggering SIGBUS in them which truncation does.)
|
||
* However if hole punching is not implemented in the kernel or file system we'll fall back to normal file
|
||
* truncation (🔪), as our goal of deallocating the data space trumps our goal of being nice to readers (💐).
|
||
*
|
||
* Note that we attempt deallocation, but failure to succeed with that is not considered fatal, as long as the
|
||
* primary job – to delete the file – is accomplished. */
|
||
|
||
if ((flags & AT_REMOVEDIR) == 0) {
|
||
truncate_fd = openat(fd, name, O_WRONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW|O_NONBLOCK);
|
||
if (truncate_fd < 0) {
|
||
|
||
/* If this failed because the file doesn't exist propagate the error right-away. Also,
|
||
* AT_REMOVEDIR wasn't set, and we tried to open the file for writing, which means EISDIR is
|
||
* returned when this is a directory but we are not supposed to delete those, hence propagate
|
||
* the error right-away too. */
|
||
if (IN_SET(errno, ENOENT, EISDIR))
|
||
return -errno;
|
||
|
||
if (errno != ELOOP) /* don't complain if this is a symlink */
|
||
log_debug_errno(errno, "Failed to open file '%s' for deallocation, ignoring: %m", name);
|
||
}
|
||
}
|
||
|
||
if (unlinkat(fd, name, flags) < 0)
|
||
return -errno;
|
||
|
||
if (truncate_fd < 0) /* Don't have a file handle, can't do more ☹️ */
|
||
return 0;
|
||
|
||
if (fstat(truncate_fd, &st) < 0) {
|
||
log_debug_errno(errno, "Failed to stat file '%s' for deallocation, ignoring.", name);
|
||
return 0;
|
||
}
|
||
|
||
if (!S_ISREG(st.st_mode) || st.st_blocks == 0 || st.st_nlink > 0)
|
||
return 0;
|
||
|
||
/* If this is a regular file, it actually took up space on disk and there are no other links it's time to
|
||
* punch-hole/truncate this to release the disk space. */
|
||
|
||
bs = MAX(st.st_blksize, 512);
|
||
l = DIV_ROUND_UP(st.st_size, bs) * bs; /* Round up to next block size */
|
||
|
||
if (fallocate(truncate_fd, FALLOC_FL_PUNCH_HOLE|FALLOC_FL_KEEP_SIZE, 0, l) >= 0)
|
||
return 0; /* Successfully punched a hole! 😊 */
|
||
|
||
/* Fall back to truncation */
|
||
if (ftruncate(truncate_fd, 0) < 0) {
|
||
log_debug_errno(errno, "Failed to truncate file to 0, ignoring: %m");
|
||
return 0;
|
||
}
|
||
|
||
return 0;
|
||
}
|
||
|
||
int fsync_directory_of_file(int fd) {
|
||
_cleanup_free_ char *path = NULL, *dn = NULL;
|
||
_cleanup_close_ int dfd = -1;
|
||
int r;
|
||
|
||
r = fd_verify_regular(fd);
|
||
if (r < 0)
|
||
return r;
|
||
|
||
r = fd_get_path(fd, &path);
|
||
if (r < 0) {
|
||
log_debug("Failed to query /proc/self/fd/%d%s: %m",
|
||
fd,
|
||
r == -EOPNOTSUPP ? ", ignoring" : "");
|
||
|
||
if (r == -EOPNOTSUPP)
|
||
/* If /proc is not available, we're most likely running in some
|
||
* chroot environment, and syncing the directory is not very
|
||
* important in that case. Let's just silently do nothing. */
|
||
return 0;
|
||
|
||
return r;
|
||
}
|
||
|
||
if (!path_is_absolute(path))
|
||
return -EINVAL;
|
||
|
||
dn = dirname_malloc(path);
|
||
if (!dn)
|
||
return -ENOMEM;
|
||
|
||
dfd = open(dn, O_RDONLY|O_CLOEXEC|O_DIRECTORY);
|
||
if (dfd < 0)
|
||
return -errno;
|
||
|
||
if (fsync(dfd) < 0)
|
||
return -errno;
|
||
|
||
return 0;
|
||
}
|