/* * loopback block device utilities * * Copyright (C) 2009-2021 Red Hat, Inc. All rights reserved. * Copyright (C) 2009-2021 Milan Broz * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version 2 * of the License, or (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. */ #include <stdlib.h> #include <string.h> #include <stdio.h> #include <unistd.h> #include <fcntl.h> #include <errno.h> #include <limits.h> #include <sys/ioctl.h> #include <sys/stat.h> #include <sys/types.h> #ifdef HAVE_SYS_SYSMACROS_H # include <sys/sysmacros.h> /* for major, minor */ #endif #include <linux/loop.h> #include "utils_loop.h" #define LOOP_DEV_MAJOR 7 #ifndef LO_FLAGS_AUTOCLEAR #define LO_FLAGS_AUTOCLEAR 4 #endif #ifndef LOOP_CTL_GET_FREE #define LOOP_CTL_GET_FREE 0x4C82 #endif #ifndef LOOP_SET_CAPACITY #define LOOP_SET_CAPACITY 0x4C07 #endif static char *crypt_loop_get_device_old(void) { char dev[20]; int i, loop_fd; struct loop_info64 lo64 = {0}; for (i = 0; i < 256; i++) { sprintf(dev, "/dev/loop%d", i); loop_fd = open(dev, O_RDONLY); if (loop_fd < 0) return NULL; if (ioctl(loop_fd, LOOP_GET_STATUS64, &lo64) && errno == ENXIO) { close(loop_fd); return strdup(dev); } close(loop_fd); } return NULL; } static char *crypt_loop_get_device(void) { char dev[64]; int i, loop_fd; struct stat st; loop_fd = open("/dev/loop-control", O_RDONLY); if (loop_fd < 0) return crypt_loop_get_device_old(); i = ioctl(loop_fd, LOOP_CTL_GET_FREE); if (i < 0) { close(loop_fd); return NULL; } close(loop_fd); if (sprintf(dev, "/dev/loop%d", i) < 0) return NULL; if (stat(dev, &st) || !S_ISBLK(st.st_mode)) return NULL; return strdup(dev); } int crypt_loop_attach(char **loop, const char *file, int offset, int autoclear, int *readonly) { struct loop_info64 lo64 = {0}; char *lo_file_name; int loop_fd = -1, file_fd = -1, r = 1; *loop = NULL; file_fd = open(file, (*readonly ? O_RDONLY : O_RDWR) | O_EXCL); if (file_fd < 0 && (errno == EROFS || errno == EACCES) && !*readonly) { *readonly = 1; file_fd = open(file, O_RDONLY | O_EXCL); } if (file_fd < 0) goto out; while (loop_fd < 0) { *loop = crypt_loop_get_device(); if (!*loop) goto out; loop_fd = open(*loop, *readonly ? O_RDONLY : O_RDWR); if (loop_fd < 0) goto out; if (ioctl(loop_fd, LOOP_SET_FD, file_fd) < 0) { if (errno != EBUSY) goto out; free(*loop); *loop = NULL; close(loop_fd); loop_fd = -1; } } lo_file_name = (char*)lo64.lo_file_name; lo_file_name[LO_NAME_SIZE-1] = '\0'; strncpy(lo_file_name, file, LO_NAME_SIZE-1); lo64.lo_offset = offset; if (autoclear) lo64.lo_flags |= LO_FLAGS_AUTOCLEAR; if (ioctl(loop_fd, LOOP_SET_STATUS64, &lo64) < 0) { (void)ioctl(loop_fd, LOOP_CLR_FD, 0); goto out; } /* Verify that autoclear is really set */ if (autoclear) { memset(&lo64, 0, sizeof(lo64)); if (ioctl(loop_fd, LOOP_GET_STATUS64, &lo64) < 0 || !(lo64.lo_flags & LO_FLAGS_AUTOCLEAR)) { (void)ioctl(loop_fd, LOOP_CLR_FD, 0); goto out; } } r = 0; out: if (r && loop_fd >= 0) close(loop_fd); if (file_fd >= 0) close(file_fd); if (r && *loop) { free(*loop); *loop = NULL; } return r ? -1 : loop_fd; } int crypt_loop_detach(const char *loop) { int loop_fd = -1, r = 1; loop_fd = open(loop, O_RDONLY); if (loop_fd < 0) return 1; if (!ioctl(loop_fd, LOOP_CLR_FD, 0)) r = 0; close(loop_fd); return r; } int crypt_loop_resize(const char *loop) { int loop_fd = -1, r = 1; loop_fd = open(loop, O_RDONLY); if (loop_fd < 0) return 1; if (!ioctl(loop_fd, LOOP_SET_CAPACITY, 0)) r = 0; close(loop_fd); return r; } static char *_ioctl_backing_file(const char *loop) { struct loop_info64 lo64 = {0}; int loop_fd; loop_fd = open(loop, O_RDONLY); if (loop_fd < 0) return NULL; if (ioctl(loop_fd, LOOP_GET_STATUS64, &lo64) < 0) { close(loop_fd); return NULL; } lo64.lo_file_name[LO_NAME_SIZE-2] = '*'; lo64.lo_file_name[LO_NAME_SIZE-1] = 0; close(loop_fd); return strdup((char*)lo64.lo_file_name); } static char *_sysfs_backing_file(const char *loop) { struct stat st; char buf[PATH_MAX]; size_t len; int fd; if (stat(loop, &st) || !S_ISBLK(st.st_mode)) return NULL; if (snprintf(buf, sizeof(buf), "/sys/dev/block/%d:%d/loop/backing_file", major(st.st_rdev), minor(st.st_rdev)) < 0) return NULL; fd = open(buf, O_RDONLY); if (fd < 0) return NULL; len = read(fd, buf, PATH_MAX); close(fd); if (len < 2) return NULL; buf[len - 1] = '\0'; return strdup(buf); } char *crypt_loop_backing_file(const char *loop) { char *bf; if (!crypt_loop_device(loop)) return NULL; bf = _sysfs_backing_file(loop); return bf ?: _ioctl_backing_file(loop); } int crypt_loop_device(const char *loop) { struct stat st; if (!loop) return 0; if (stat(loop, &st) || !S_ISBLK(st.st_mode) || major(st.st_rdev) != LOOP_DEV_MAJOR) return 0; return 1; }