/*
* Metadata on-disk locking for processes serialization
*
* Copyright (C) 2016-2020 Red Hat, Inc. All rights reserved.
* Copyright (C) 2016-2020 Ondrej Kozina
*
* 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 <errno.h>
#include <linux/limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#ifdef HAVE_SYS_SYSMACROS_H
# include <sys/sysmacros.h> /* for major, minor */
#endif
#include <libgen.h>
#include <assert.h>
#include "internal.h"
#include "utils_device_locking.h"
#define same_inode(buf1, buf2) \
((buf1).st_ino == (buf2).st_ino && \
(buf1).st_dev == (buf2).st_dev)
enum lock_type {
DEV_LOCK_READ = 0,
DEV_LOCK_WRITE
};
enum lock_mode {
DEV_LOCK_FILE = 0,
DEV_LOCK_BDEV,
DEV_LOCK_NAME
};
struct crypt_lock_handle {
unsigned refcnt;
int flock_fd;
enum lock_type type;
enum lock_mode mode;
union {
struct {
dev_t devno;
} bdev;
struct {
char *name;
} name;
} u;
};
static int resource_by_name(char *res, size_t res_size, const char *name, bool fullpath)
{
int r;
if (fullpath)
r = snprintf(res, res_size, "%s/LN_%s", DEFAULT_LUKS2_LOCK_PATH, name);
else
r = snprintf(res, res_size, "LN_%s", name);
return (r < 0 || (size_t)r >= res_size) ? -EINVAL : 0;
}
static int resource_by_devno(char *res, size_t res_size, dev_t devno, unsigned fullpath)
{
int r;
if (fullpath)
r = snprintf(res, res_size, "%s/L_%d:%d", DEFAULT_LUKS2_LOCK_PATH, major(devno), minor(devno));
else
r = snprintf(res, res_size, "L_%d:%d", major(devno), minor(devno));
return (r < 0 || (size_t)r >= res_size) ? -EINVAL : 0;
}
static int open_lock_dir(struct crypt_device *cd, const char *dir, const char *base)
{
int dirfd, lockdfd;
dirfd = open(dir, O_RDONLY | O_DIRECTORY | O_CLOEXEC);
if (dirfd < 0) {
log_dbg(cd, "Failed to open directory %s: (%d: %s).", dir, errno, strerror(errno));
if (errno == ENOTDIR || errno == ENOENT)
log_err(cd, _("Locking aborted. The locking path %s/%s is unusable (not a directory or missing)."), dir, base);
return -EINVAL;
}
lockdfd = openat(dirfd, base, O_RDONLY | O_NOFOLLOW | O_DIRECTORY | O_CLOEXEC);
if (lockdfd < 0) {
if (errno == ENOENT) {
log_std(cd, _("WARNING: Locking directory %s/%s is missing!\n"), dir, base);
/* success or failure w/ errno == EEXIST either way just try to open the 'base' directory again */
if (mkdirat(dirfd, base, DEFAULT_LUKS2_LOCK_DIR_PERMS) && errno != EEXIST)
log_dbg(cd, "Failed to create directory %s in %s (%d: %s).", base, dir, errno, strerror(errno));
else
lockdfd = openat(dirfd, base, O_RDONLY | O_NOFOLLOW | O_DIRECTORY | O_CLOEXEC);
} else {
log_dbg(cd, "Failed to open directory %s/%s: (%d: %s)", dir, base, errno, strerror(errno));
if (errno == ENOTDIR || errno == ELOOP)
log_err(cd, _("Locking aborted. The locking path %s/%s is unusable (%s is not a directory)."), dir, base, base);
}
}
close(dirfd);
return lockdfd >= 0 ? lockdfd : -EINVAL;
}
static int open_resource(struct crypt_device *cd, const char *res)
{
int err, lockdir_fd, r;
char dir[] = DEFAULT_LUKS2_LOCK_PATH,
base[] = DEFAULT_LUKS2_LOCK_PATH;
lockdir_fd = open_lock_dir(cd, dirname(dir), basename(base));
if (lockdir_fd < 0)
return -EINVAL;
log_dbg(cd, "Opening lock resource file %s/%s", DEFAULT_LUKS2_LOCK_PATH, res);
r = openat(lockdir_fd, res, O_CREAT | O_NOFOLLOW | O_RDWR | O_CLOEXEC, 0777);
err = errno;
close(lockdir_fd);
return r < 0 ? -err : r;
}
static int acquire_lock_handle(struct crypt_device *cd, struct device *device, struct crypt_lock_handle *h)
{
char res[PATH_MAX];
int dev_fd, fd;
struct stat st;
dev_fd = open(device_path(device), O_RDONLY | O_NONBLOCK | O_CLOEXEC);
if (dev_fd < 0)
return -EINVAL;
if (fstat(dev_fd, &st)) {
close(dev_fd);
return -EINVAL;
}
if (S_ISBLK(st.st_mode)) {
if (resource_by_devno(res, sizeof(res), st.st_rdev, 0)) {
close(dev_fd);
return -EINVAL;
}
fd = open_resource(cd, res);
close(dev_fd);
if (fd < 0)
return fd;
h->flock_fd = fd;
h->u.bdev.devno = st.st_rdev;
h->mode = DEV_LOCK_BDEV;
} else if (S_ISREG(st.st_mode)) {
// FIXME: workaround for nfsv4
fd = open(device_path(device), O_RDWR | O_NONBLOCK | O_CLOEXEC);
if (fd < 0)
h->flock_fd = dev_fd;
else {
h->flock_fd = fd;
close(dev_fd);
}
h->mode = DEV_LOCK_FILE;
} else {
/* Wrong device type */
close(dev_fd);
return -EINVAL;
}
return 0;
}
static int acquire_lock_handle_by_name(struct crypt_device *cd, const char *name, struct crypt_lock_handle *h)
{
char res[PATH_MAX];
int fd;
h->u.name.name = strdup(name);
if (!h->u.name.name)
return -ENOMEM;
if (resource_by_name(res, sizeof(res), name, false)) {
free(h->u.name.name);
return -EINVAL;
}
fd = open_resource(cd, res);
if (fd < 0) {
free(h->u.name.name);
return fd;
}
h->flock_fd = fd;
h->mode = DEV_LOCK_NAME;
return 0;
}
static void release_lock_handle(struct crypt_device *cd, struct crypt_lock_handle *h)
{
char res[PATH_MAX];
struct stat buf_a, buf_b;
if ((h->mode == DEV_LOCK_NAME) && /* was it name lock */
!flock(h->flock_fd, LOCK_EX | LOCK_NB) && /* lock to drop the file */
!resource_by_name(res, sizeof(res), h->u.name.name, true) && /* acquire lock resource name */
!fstat(h->flock_fd, &buf_a) && /* read inode id referred by fd */
!stat(res, &buf_b) && /* does path file still exist? */
same_inode(buf_a, buf_b)) { /* is it same id as the one referenced by fd? */
/* coverity[toctou] */
if (unlink(res)) /* yes? unlink the file */
log_dbg(cd, "Failed to unlink resource file: %s", res);
}
if ((h->mode == DEV_LOCK_BDEV) && /* was it block device */
!flock(h->flock_fd, LOCK_EX | LOCK_NB) && /* lock to drop the file */
!resource_by_devno(res, sizeof(res), h->u.bdev.devno, 1) && /* acquire lock resource name */
!fstat(h->flock_fd, &buf_a) && /* read inode id referred by fd */
!stat(res, &buf_b) && /* does path file still exist? */
same_inode(buf_a, buf_b)) { /* is it same id as the one referenced by fd? */
/* coverity[toctou] */
if (unlink(res)) /* yes? unlink the file */
log_dbg(cd, "Failed to unlink resource file: %s", res);
}
if (h->mode == DEV_LOCK_NAME)
free(h->u.name.name);
if (close(h->flock_fd))
log_dbg(cd, "Failed to close lock resource fd (%d).", h->flock_fd);
}
int device_locked(struct crypt_lock_handle *h)
{
return (h && (h->type == DEV_LOCK_READ || h->type == DEV_LOCK_WRITE));
}
int device_locked_readonly(struct crypt_lock_handle *h)
{
return (h && h->type == DEV_LOCK_READ);
}
static int verify_lock_handle(const char *device_path, struct crypt_lock_handle *h)
{
char res[PATH_MAX];
struct stat lck_st, res_st;
/* we locked a regular file, check during device_open() instead. No reason to check now */
if (h->mode == DEV_LOCK_FILE)
return 0;
if (h->mode == DEV_LOCK_NAME) {
if (resource_by_name(res, sizeof(res), h->u.name.name, true))
return -EINVAL;
} else if (h->mode == DEV_LOCK_BDEV) {
if (resource_by_devno(res, sizeof(res), h->u.bdev.devno, true))
return -EINVAL;
} else
return -EINVAL;
if (fstat(h->flock_fd, &lck_st))
return -EINVAL;
return (stat(res, &res_st) || !same_inode(lck_st, res_st)) ? -EAGAIN : 0;
}
static unsigned device_lock_inc(struct crypt_lock_handle *h)
{
return ++h->refcnt;
}
static unsigned device_lock_dec(struct crypt_lock_handle *h)
{
assert(h->refcnt);
return --h->refcnt;
}
static int acquire_and_verify(struct crypt_device *cd, struct device *device, const char *resource, int flock_op, struct crypt_lock_handle **lock)
{
int r;
struct crypt_lock_handle *h;
if (device && resource)
return -EINVAL;
if (!(h = malloc(sizeof(*h))))
return -ENOMEM;
do {
r = device ? acquire_lock_handle(cd, device, h) : acquire_lock_handle_by_name(cd, resource, h);
if (r < 0)
break;
if (flock(h->flock_fd, flock_op)) {
log_dbg(cd, "Flock on fd %d failed with errno %d.", h->flock_fd, errno);
r = (errno == EWOULDBLOCK) ? -EBUSY : -EINVAL;
release_lock_handle(cd, h);
break;
}
log_dbg(cd, "Verifying lock handle for %s.", device ? device_path(device) : resource);
/*
* check whether another libcryptsetup process removed resource file before this
* one managed to flock() it. See release_lock_handle() for details
*/
r = verify_lock_handle(device_path(device), h);
if (r < 0) {
if (flock(h->flock_fd, LOCK_UN))
log_dbg(cd, "flock on fd %d failed.", h->flock_fd);
release_lock_handle(cd, h);
log_dbg(cd, "Lock handle verification failed.");
}
} while (r == -EAGAIN);
if (r < 0) {
free(h);
return r;
}
*lock = h;
return 0;
}
int device_read_lock_internal(struct crypt_device *cd, struct device *device)
{
int r;
struct crypt_lock_handle *h;
if (!device)
return -EINVAL;
h = device_get_lock_handle(device);
if (device_locked(h)) {
device_lock_inc(h);
log_dbg(cd, "Device %s READ lock (or higher) already held.", device_path(device));
return 0;
}
log_dbg(cd, "Acquiring read lock for device %s.", device_path(device));
r = acquire_and_verify(cd, device, NULL, LOCK_SH, &h);
if (r < 0)
return r;
h->type = DEV_LOCK_READ;
h->refcnt = 1;
device_set_lock_handle(device, h);
log_dbg(cd, "Device %s READ lock taken.", device_path(device));
return 0;
}
int device_write_lock_internal(struct crypt_device *cd, struct device *device)
{
int r;
struct crypt_lock_handle *h;
if (!device)
return -EINVAL;
h = device_get_lock_handle(device);
if (device_locked(h)) {
log_dbg(cd, "Device %s WRITE lock already held.", device_path(device));
return device_lock_inc(h);
}
log_dbg(cd, "Acquiring write lock for device %s.", device_path(device));
r = acquire_and_verify(cd, device, NULL, LOCK_EX, &h);
if (r < 0)
return r;
h->type = DEV_LOCK_WRITE;
h->refcnt = 1;
device_set_lock_handle(device, h);
log_dbg(cd, "Device %s WRITE lock taken.", device_path(device));
return 1;
}
int crypt_read_lock(struct crypt_device *cd, const char *resource, bool blocking, struct crypt_lock_handle **lock)
{
int r;
struct crypt_lock_handle *h;
if (!resource)
return -EINVAL;
log_dbg(cd, "Acquiring %sblocking read lock for resource %s.", blocking ? "" : "non", resource);
r = acquire_and_verify(cd, NULL, resource, LOCK_SH | (blocking ? 0 : LOCK_NB), &h);
if (r < 0)
return r;
h->type = DEV_LOCK_READ;
h->refcnt = 1;
log_dbg(cd, "READ lock for resource %s taken.", resource);
*lock = h;
return 0;
}
int crypt_write_lock(struct crypt_device *cd, const char *resource, bool blocking, struct crypt_lock_handle **lock)
{
int r;
struct crypt_lock_handle *h;
if (!resource)
return -EINVAL;
log_dbg(cd, "Acquiring %sblocking write lock for resource %s.", blocking ? "" : "non", resource);
r = acquire_and_verify(cd, NULL, resource, LOCK_EX | (blocking ? 0 : LOCK_NB), &h);
if (r < 0)
return r;
h->type = DEV_LOCK_WRITE;
h->refcnt = 1;
log_dbg(cd, "WRITE lock for resource %s taken.", resource);
*lock = h;
return 0;
}
static void unlock_internal(struct crypt_device *cd, struct crypt_lock_handle *h)
{
if (flock(h->flock_fd, LOCK_UN))
log_dbg(cd, "flock on fd %d failed.", h->flock_fd);
release_lock_handle(cd, h);
free(h);
}
void crypt_unlock_internal(struct crypt_device *cd, struct crypt_lock_handle *h)
{
if (!h)
return;
/* nested locks are illegal */
assert(!device_lock_dec(h));
log_dbg(cd, "Unlocking %s lock for resource %s.",
device_locked_readonly(h) ? "READ" : "WRITE", h->u.name.name);
unlock_internal(cd, h);
}
void device_unlock_internal(struct crypt_device *cd, struct device *device)
{
bool readonly;
struct crypt_lock_handle *h = device_get_lock_handle(device);
unsigned u = device_lock_dec(h);
if (u)
return;
readonly = device_locked_readonly(h);
unlock_internal(cd, h);
log_dbg(cd, "Device %s %s lock released.", device_path(device),
readonly ? "READ" : "WRITE");
device_set_lock_handle(device, NULL);
}
int device_locked_verify(struct crypt_device *cd, int dev_fd, struct crypt_lock_handle *h)
{
char res[PATH_MAX];
struct stat dev_st, lck_st, st;
if (fstat(dev_fd, &dev_st) || fstat(h->flock_fd, &lck_st))
return 1;
/* if device handle is regular file the handle must match the lock handle */
if (S_ISREG(dev_st.st_mode)) {
log_dbg(cd, "Veryfing locked device handle (regular file)");
if (!same_inode(dev_st, lck_st))
return 1;
} else if (S_ISBLK(dev_st.st_mode)) {
log_dbg(cd, "Veryfing locked device handle (bdev)");
if (resource_by_devno(res, sizeof(res), dev_st.st_rdev, 1) ||
stat(res, &st) ||
!same_inode(lck_st, st))
return 1;
} else
return 1;
return 0;
}