loop.c

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	memset(info, 0, sizeof(*info));
	info->lo_number = info64->lo_number;
	info->lo_device = info64->lo_device;
	info->lo_inode = info64->lo_inode;
	info->lo_rdevice = info64->lo_rdevice;
	info->lo_offset = info64->lo_offset;
	info->lo_encrypt_type = info64->lo_encrypt_type;
	info->lo_encrypt_key_size = info64->lo_encrypt_key_size;
	info->lo_flags = info64->lo_flags;
	info->lo_init[0] = info64->lo_init[0];
	info->lo_init[1] = info64->lo_init[1];
	if (info->lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
		memcpy(info->lo_name, info64->lo_crypt_name, LO_NAME_SIZE);
	else
		memcpy(info->lo_name, info64->lo_file_name, LO_NAME_SIZE);
	memcpy(info->lo_encrypt_key, info64->lo_encrypt_key, LO_KEY_SIZE);

	/* error in case values were truncated */
	if (info->lo_device != info64->lo_device ||
	    info->lo_rdevice != info64->lo_rdevice ||
	    info->lo_inode != info64->lo_inode ||
	    info->lo_offset != info64->lo_offset)
		return -EOVERFLOW;

	return 0;
}

static int
loop_set_status_old(struct loop_device *lo, const struct loop_info __user *arg)
{
	struct loop_info info;
	struct loop_info64 info64;

	if (copy_from_user(&info, arg, sizeof (struct loop_info)))
		return -EFAULT;
	loop_info64_from_old(&info, &info64);
	return loop_set_status(lo, &info64);
}

static int
loop_set_status64(struct loop_device *lo, const struct loop_info64 __user *arg)
{
	struct loop_info64 info64;

	if (copy_from_user(&info64, arg, sizeof (struct loop_info64)))
		return -EFAULT;
	return loop_set_status(lo, &info64);
}

static int
loop_get_status_old(struct loop_device *lo, struct loop_info __user *arg) {
	struct loop_info info;
	struct loop_info64 info64;
	int err = 0;

	if (!arg)
		err = -EINVAL;
	if (!err)
		err = loop_get_status(lo, &info64);
	if (!err)
		err = loop_info64_to_old(&info64, &info);
	if (!err && copy_to_user(arg, &info, sizeof(info)))
		err = -EFAULT;

	return err;
}

static int
loop_get_status64(struct loop_device *lo, struct loop_info64 __user *arg) {
	struct loop_info64 info64;
	int err = 0;

	if (!arg)
		err = -EINVAL;
	if (!err)
		err = loop_get_status(lo, &info64);
	if (!err && copy_to_user(arg, &info64, sizeof(info64)))
		err = -EFAULT;

	return err;
}

static int lo_ioctl(struct inode * inode, struct file * file,
	unsigned int cmd, unsigned long arg)
{
	struct loop_device *lo = inode->i_bdev->bd_disk->private_data;
	int err;

	mutex_lock(&lo->lo_ctl_mutex);
	switch (cmd) {
	case LOOP_SET_FD:
		err = loop_set_fd(lo, file, inode->i_bdev, arg);
		break;
	case LOOP_CHANGE_FD:
		err = loop_change_fd(lo, file, inode->i_bdev, arg);
		break;
	case LOOP_CLR_FD:
		err = loop_clr_fd(lo, inode->i_bdev);
		break;
	case LOOP_SET_STATUS:
		err = loop_set_status_old(lo, (struct loop_info __user *) arg);
		break;
	case LOOP_GET_STATUS:
		err = loop_get_status_old(lo, (struct loop_info __user *) arg);
		break;
	case LOOP_SET_STATUS64:
		err = loop_set_status64(lo, (struct loop_info64 __user *) arg);
		break;
	case LOOP_GET_STATUS64:
		err = loop_get_status64(lo, (struct loop_info64 __user *) arg);
		break;
	default:
		err = lo->ioctl ? lo->ioctl(lo, cmd, arg) : -EINVAL;
	}
	mutex_unlock(&lo->lo_ctl_mutex);
	return err;
}

#ifdef CONFIG_COMPAT
struct compat_loop_info {
	compat_int_t	lo_number;      /* ioctl r/o */
	compat_dev_t	lo_device;      /* ioctl r/o */
	compat_ulong_t	lo_inode;       /* ioctl r/o */
	compat_dev_t	lo_rdevice;     /* ioctl r/o */
	compat_int_t	lo_offset;
	compat_int_t	lo_encrypt_type;
	compat_int_t	lo_encrypt_key_size;    /* ioctl w/o */
	compat_int_t	lo_flags;       /* ioctl r/o */
	char		lo_name[LO_NAME_SIZE];
	unsigned char	lo_encrypt_key[LO_KEY_SIZE]; /* ioctl w/o */
	compat_ulong_t	lo_init[2];
	char		reserved[4];
};

/*
 * Transfer 32-bit compatibility structure in userspace to 64-bit loop info
 * - noinlined to reduce stack space usage in main part of driver
 */
static noinline int
loop_info64_from_compat(const struct compat_loop_info __user *arg,
			struct loop_info64 *info64)
{
	struct compat_loop_info info;

	if (copy_from_user(&info, arg, sizeof(info)))
		return -EFAULT;

	memset(info64, 0, sizeof(*info64));
	info64->lo_number = info.lo_number;
	info64->lo_device = info.lo_device;
	info64->lo_inode = info.lo_inode;
	info64->lo_rdevice = info.lo_rdevice;
	info64->lo_offset = info.lo_offset;
	info64->lo_sizelimit = 0;
	info64->lo_encrypt_type = info.lo_encrypt_type;
	info64->lo_encrypt_key_size = info.lo_encrypt_key_size;
	info64->lo_flags = info.lo_flags;
	info64->lo_init[0] = info.lo_init[0];
	info64->lo_init[1] = info.lo_init[1];
	if (info.lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
		memcpy(info64->lo_crypt_name, info.lo_name, LO_NAME_SIZE);
	else
		memcpy(info64->lo_file_name, info.lo_name, LO_NAME_SIZE);
	memcpy(info64->lo_encrypt_key, info.lo_encrypt_key, LO_KEY_SIZE);
	return 0;
}

/*
 * Transfer 64-bit loop info to 32-bit compatibility structure in userspace
 * - noinlined to reduce stack space usage in main part of driver
 */
static noinline int
loop_info64_to_compat(const struct loop_info64 *info64,
		      struct compat_loop_info __user *arg)
{
	struct compat_loop_info info;

	memset(&info, 0, sizeof(info));
	info.lo_number = info64->lo_number;
	info.lo_device = info64->lo_device;
	info.lo_inode = info64->lo_inode;
	info.lo_rdevice = info64->lo_rdevice;
	info.lo_offset = info64->lo_offset;
	info.lo_encrypt_type = info64->lo_encrypt_type;
	info.lo_encrypt_key_size = info64->lo_encrypt_key_size;
	info.lo_flags = info64->lo_flags;
	info.lo_init[0] = info64->lo_init[0];
	info.lo_init[1] = info64->lo_init[1];
	if (info.lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
		memcpy(info.lo_name, info64->lo_crypt_name, LO_NAME_SIZE);
	else
		memcpy(info.lo_name, info64->lo_file_name, LO_NAME_SIZE);
	memcpy(info.lo_encrypt_key, info64->lo_encrypt_key, LO_KEY_SIZE);

	/* error in case values were truncated */
	if (info.lo_device != info64->lo_device ||
	    info.lo_rdevice != info64->lo_rdevice ||
	    info.lo_inode != info64->lo_inode ||
	    info.lo_offset != info64->lo_offset ||
	    info.lo_init[0] != info64->lo_init[0] ||
	    info.lo_init[1] != info64->lo_init[1])
		return -EOVERFLOW;

	if (copy_to_user(arg, &info, sizeof(info)))
		return -EFAULT;
	return 0;
}

static int
loop_set_status_compat(struct loop_device *lo,
		       const struct compat_loop_info __user *arg)
{
	struct loop_info64 info64;
	int ret;

	ret = loop_info64_from_compat(arg, &info64);
	if (ret < 0)
		return ret;
	return loop_set_status(lo, &info64);
}

static int
loop_get_status_compat(struct loop_device *lo,
		       struct compat_loop_info __user *arg)
{
	struct loop_info64 info64;
	int err = 0;

	if (!arg)
		err = -EINVAL;
	if (!err)
		err = loop_get_status(lo, &info64);
	if (!err)
		err = loop_info64_to_compat(&info64, arg);
	return err;
}

static long lo_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
	struct inode *inode = file->f_path.dentry->d_inode;
	struct loop_device *lo = inode->i_bdev->bd_disk->private_data;
	int err;

	switch(cmd) {
	case LOOP_SET_STATUS:
		mutex_lock(&lo->lo_ctl_mutex);
		err = loop_set_status_compat(
			lo, (const struct compat_loop_info __user *) arg);
		mutex_unlock(&lo->lo_ctl_mutex);
		break;
	case LOOP_GET_STATUS:
		mutex_lock(&lo->lo_ctl_mutex);
		err = loop_get_status_compat(
			lo, (struct compat_loop_info __user *) arg);
		mutex_unlock(&lo->lo_ctl_mutex);
		break;
	case LOOP_CLR_FD:
	case LOOP_GET_STATUS64:
	case LOOP_SET_STATUS64:
		arg = (unsigned long) compat_ptr(arg);
	case LOOP_SET_FD:
	case LOOP_CHANGE_FD:
		err = lo_ioctl(inode, file, cmd, arg);
		break;
	default:
		err = -ENOIOCTLCMD;
		break;
	}
	return err;
}
#endif

static int lo_open(struct inode *inode, struct file *file)
{
	struct loop_device *lo = inode->i_bdev->bd_disk->private_data;

	mutex_lock(&lo->lo_ctl_mutex);
	lo->lo_refcnt++;
	mutex_unlock(&lo->lo_ctl_mutex);

	return 0;
}

static int lo_release(struct inode *inode, struct file *file)
{
	struct loop_device *lo = inode->i_bdev->bd_disk->private_data;

	mutex_lock(&lo->lo_ctl_mutex);
	--lo->lo_refcnt;
	mutex_unlock(&lo->lo_ctl_mutex);

	return 0;
}

static struct block_device_operations lo_fops = {
	.owner =	THIS_MODULE,
	.open =		lo_open,
	.release =	lo_release,
	.ioctl =	lo_ioctl,
#ifdef CONFIG_COMPAT
	.compat_ioctl =	lo_compat_ioctl,
#endif
};

/*
 * And now the modules code and kernel interface.
 */
static int max_loop;
module_param(max_loop, int, 0);
MODULE_PARM_DESC(max_loop, "Maximum number of loop devices");
MODULE_LICENSE("GPL");
MODULE_ALIAS_BLOCKDEV_MAJOR(LOOP_MAJOR);

int loop_register_transfer(struct loop_func_table *funcs)
{
	unsigned int n = funcs->number;

	if (n >= MAX_LO_CRYPT || xfer_funcs[n])
		return -EINVAL;
	xfer_funcs[n] = funcs;
	return 0;
}

int loop_unregister_transfer(int number)
{
	unsigned int n = number;
	struct loop_device *lo;
	struct loop_func_table *xfer;

	if (n == 0 || n >= MAX_LO_CRYPT || (xfer = xfer_funcs[n]) == NULL)
		return -EINVAL;

	xfer_funcs[n] = NULL;

	list_for_each_entry(lo, &loop_devices, lo_list) {
		mutex_lock(&lo->lo_ctl_mutex);

		if (lo->lo_encryption == xfer)
			loop_release_xfer(lo);

		mutex_unlock(&lo->lo_ctl_mutex);
	}

	return 0;
}

EXPORT_SYMBOL(loop_register_transfer);
EXPORT_SYMBOL(loop_unregister_transfer);

static struct loop_device *loop_alloc(int i)
{
	struct loop_device *lo;
	struct gendisk *disk;

	lo = kzalloc(sizeof(*lo), GFP_KERNEL);
	if (!lo)
		goto out;

	lo->lo_queue = blk_alloc_queue(GFP_KERNEL);
	if (!lo->lo_queue)
		goto out_free_dev;

	disk = lo->lo_disk = alloc_disk(1);
	if (!disk)
		goto out_free_queue;

	mutex_init(&lo->lo_ctl_mutex);
	lo->lo_number		= i;
	lo->lo_thread		= NULL;
	init_waitqueue_head(&lo->lo_event);
	spin_lock_init(&lo->lo_lock);
	disk->major		= LOOP_MAJOR;
	disk->first_minor	= i;
	disk->fops		= &lo_fops;
	disk->private_data	= lo;
	disk->queue		= lo->lo_queue;
	sprintf(disk->disk_name, "loop%d", i);
	return lo;

out_free_queue:
	blk_cleanup_queue(lo->lo_queue);
out_free_dev:
	kfree(lo);
out:
	return NULL;
}

static void loop_free(struct loop_device *lo)
{
	blk_cleanup_queue(lo->lo_queue);
	put_disk(lo->lo_disk);
	list_del(&lo->lo_list);
	kfree(lo);
}

static struct loop_device *loop_init_one(int i)
{
	struct loop_device *lo;

	list_for_each_entry(lo, &loop_devices, lo_list) {
		if (lo->lo_number == i)
			return lo;
	}

	lo = loop_alloc(i);
	if (lo) {
		add_disk(lo->lo_disk);
		list_add_tail(&lo->lo_list, &loop_devices);
	}
	return lo;
}

static void loop_del_one(struct loop_device *lo)
{
	del_gendisk(lo->lo_disk);
	loop_free(lo);
}

static struct kobject *loop_probe(dev_t dev, int *part, void *data)
{
	struct loop_device *lo;
	struct kobject *kobj;

	mutex_lock(&loop_devices_mutex);
	lo = loop_init_one(dev & MINORMASK);
	kobj = lo ? get_disk(lo->lo_disk) : ERR_PTR(-ENOMEM);
	mutex_unlock(&loop_devices_mutex);

	*part = 0;
	return kobj;
}

static int __init loop_init(void)
{
	int i, nr;
	unsigned long range;
	struct loop_device *lo, *next;

	/*
	 * loop module now has a feature to instantiate underlying device
	 * structure on-demand, provided that there is an access dev node.
	 * However, this will not work well with user space tool that doesn't
	 * know about such "feature".  In order to not break any existing
	 * tool, we do the following:
	 *
	 * (1) if max_loop is specified, create that many upfront, and this
	 *     also becomes a hard limit.
	 * (2) if max_loop is not specified, create 8 loop device on module
	 *     load, user can further extend loop device by create dev node
	 *     themselves and have kernel automatically instantiate actual
	 *     device on-demand.
	 */
	if (max_loop > 1UL << MINORBITS)
		return -EINVAL;

	if (max_loop) {
		nr = max_loop;
		range = max_loop;
	} else {
		nr = 8;
		range = 1UL << MINORBITS;
	}

	if (register_blkdev(LOOP_MAJOR, "loop"))
		return -EIO;

	for (i = 0; i < nr; i++) {
		lo = loop_alloc(i);
		if (!lo)
			goto Enomem;
		list_add_tail(&lo->lo_list, &loop_devices);
	}

	/* point of no return */

	list_for_each_entry(lo, &loop_devices, lo_list)
		add_disk(lo->lo_disk);

	blk_register_region(MKDEV(LOOP_MAJOR, 0), range,
				  THIS_MODULE, loop_probe, NULL, NULL);

	printk(KERN_INFO "loop: module loaded\n");
	return 0;

Enomem:
	printk(KERN_INFO "loop: out of memory\n");

	list_for_each_entry_safe(lo, next, &loop_devices, lo_list)
		loop_free(lo);

	unregister_blkdev(LOOP_MAJOR, "loop");
	return -ENOMEM;
}

static void __exit loop_exit(void)
{
	unsigned long range;
	struct loop_device *lo, *next;

	range = max_loop ? max_loop :  1UL << MINORBITS;

	list_for_each_entry_safe(lo, next, &loop_devices, lo_list)
		loop_del_one(lo);

	blk_unregister_region(MKDEV(LOOP_MAJOR, 0), range);
	unregister_blkdev(LOOP_MAJOR, "loop");
}

module_init(loop_init);
module_exit(loop_exit);

#ifndef MODULE
static int __init max_loop_setup(char *str)
{
	max_loop = simple_strtol(str, NULL, 0);
	return 1;
}

__setup("max_loop=", max_loop_setup);
#endif