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/* Copyright (c) 2015-2018 Dovecot authors, see the included COPYING file */
#include "lib.h"
#include "str.h"
#include "safe-mkstemp.h"
#include "mkdir-parents.h"
#include "file-lock.h"
#include "file-create-locked.h"
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>
/* Try mkdir() + lock creation multiple times. This allows the lock file
creation to work even while the directory is simultaneously being
rmdir()ed. */
#define MAX_MKDIR_COUNT 10
#define MAX_RETRY_COUNT 1000
static int
try_lock_existing(int fd, const char *path,
const struct file_create_settings *set,
struct file_lock **lock_r, const char **error_r)
{
struct file_lock_settings lock_set = set->lock_settings;
struct stat st1, st2;
int ret;
lock_set.unlink_on_free = FALSE;
lock_set.close_on_free = FALSE;
if (fstat(fd, &st1) < 0) {
*error_r = t_strdup_printf("fstat(%s) failed: %m", path);
return -1;
}
if (file_wait_lock(fd, path, F_WRLCK, &lock_set, set->lock_timeout_secs,
lock_r, error_r) <= 0)
return -1;
if (stat(path, &st2) == 0) {
ret = st1.st_ino == st2.st_ino &&
CMP_DEV_T(st1.st_dev, st2.st_dev) ? 1 : 0;
} else if (errno == ENOENT) {
ret = 0;
} else {
*error_r = t_strdup_printf("stat(%s) failed: %m", path);
ret = -1;
}
if (ret <= 0) {
/* the fd is closed next - no need to unlock */
file_lock_free(lock_r);
} else {
file_lock_set_unlink_on_free(
*lock_r, set->lock_settings.unlink_on_free);
file_lock_set_close_on_free(
*lock_r, set->lock_settings.close_on_free);
}
return ret;
}
static int
try_mkdir(const char *path, const struct file_create_settings *set,
const char **error_r)
{
uid_t uid = set->mkdir_uid != 0 ? set->mkdir_uid : (uid_t)-1;
gid_t gid = set->mkdir_gid != 0 ? set->mkdir_gid : (gid_t)-1;
const char *p = strrchr(path, '/');
if (p == NULL)
return 0;
const char *dir = t_strdup_until(path, p);
int ret;
if (uid != (uid_t)-1)
ret = mkdir_parents_chown(dir, set->mkdir_mode, uid, gid);
else {
ret = mkdir_parents_chgrp(dir, set->mkdir_mode,
gid, set->gid_origin);
}
if (ret < 0 && errno != EEXIST) {
*error_r = t_strdup_printf("mkdir_parents(%s) failed: %m", dir);
return -1;
}
return 1;
}
static int
try_create_new(const char *path, const struct file_create_settings *set,
int *fd_r, struct file_lock **lock_r, const char **error_r)
{
string_t *temp_path = t_str_new(128);
int fd, orig_errno, ret = 1;
int mode = set->mode != 0 ? set->mode : 0600;
uid_t uid = set->uid != 0 ? set->uid : (uid_t)-1;
uid_t gid = set->gid != 0 ? set->gid : (gid_t)-1;
str_append(temp_path, path);
for (unsigned int i = 0; ret > 0; i++) {
if (uid != (uid_t)-1)
fd = safe_mkstemp(temp_path, mode, uid, gid);
else
fd = safe_mkstemp_group(temp_path, mode, gid, set->gid_origin);
if (fd != -1 || errno != ENOENT || set->mkdir_mode == 0 ||
i >= MAX_MKDIR_COUNT)
break;
int orig_errno = errno;
if ((ret = try_mkdir(path, set, error_r)) < 0)
return -1;
errno = orig_errno;
}
if (fd == -1) {
*error_r = t_strdup_printf("safe_mkstemp(%s) failed: %m", path);
return -1;
}
struct file_lock_settings lock_set = set->lock_settings;
lock_set.unlink_on_free = FALSE;
lock_set.close_on_free = FALSE;
ret = -1;
if (file_try_lock(fd, str_c(temp_path), F_WRLCK, &lock_set,
lock_r, error_r) <= 0) {
} else if (link(str_c(temp_path), path) < 0) {
if (errno == EEXIST) {
/* just created by somebody else */
ret = 0;
} else if (errno == ENOENT) {
/* nobody should be deleting the temp file unless the
entire directory is deleted. */
*error_r = t_strdup_printf(
"Temporary file %s was unexpectedly deleted",
str_c(temp_path));
} else {
*error_r = t_strdup_printf("link(%s, %s) failed: %m",
str_c(temp_path), path);
}
file_lock_free(lock_r);
} else {
file_lock_set_path(*lock_r, path);
file_lock_set_unlink_on_free(
*lock_r, set->lock_settings.unlink_on_free);
file_lock_set_close_on_free(
*lock_r, set->lock_settings.close_on_free);
i_unlink_if_exists(str_c(temp_path));
*fd_r = fd;
return 1;
}
orig_errno = errno;
i_close_fd(&fd);
i_unlink_if_exists(str_c(temp_path));
errno = orig_errno;
return ret;
}
int file_create_locked(const char *path, const struct file_create_settings *set,
struct file_lock **lock_r, bool *created_r,
const char **error_r)
{
unsigned int i;
int fd, ret;
for (i = 0; i < MAX_RETRY_COUNT; i++) {
fd = open(path, O_RDWR);
if (fd != -1) {
ret = try_lock_existing(fd, path, set, lock_r, error_r);
if (ret > 0) {
/* successfully locked an existing file */
*created_r = FALSE;
return fd;
}
i_close_fd(&fd);
if (ret < 0)
return -1;
} else if (errno != ENOENT) {
*error_r = t_strdup_printf("open(%s) failed: %m", path);
return -1;
} else {
/* try to create the file */
ret = try_create_new(path, set, &fd, lock_r, error_r);
if (ret < 0)
return -1;
if (ret > 0) {
/* successfully created a new locked file */
*created_r = TRUE;
return fd;
}
/* the file was just created - try again opening and
locking it */
}
}
*error_r = t_strdup_printf("Creating a locked file %s keeps failing", path);
errno = EINVAL;
return -1;
}
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