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Commit 7fde62bf authored by Chris Mason's avatar Chris Mason
Browse files

Btrfs: buffer results in the space_info ioctl 



The space_info ioctl was using copy_to_user inside rcu_read_lock.  This
commit changes things to copy into a buffer first and then dump the
result down to userland.

Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent ce769a29

fs/btrfs/ioctl.c

+46 −11
Original line number Diff line number Diff line
@@ -1848,39 +1848,74 @@ long btrfs_ioctl_space_info(struct btrfs_root *root, void __user *arg) 
	struct btrfs_ioctl_space_args space_args;

	struct btrfs_ioctl_space_info space;

	struct btrfs_ioctl_space_info *dest;

	struct btrfs_ioctl_space_info *dest_orig;

	struct btrfs_ioctl_space_info *user_dest;

	struct btrfs_space_info *info;

	int alloc_size;

	int ret = 0;

	int slot_count = 0;



	if (copy_from_user(&space_args,

			   (struct btrfs_ioctl_space_args __user *)arg,

			   sizeof(space_args)))

		return -EFAULT;



	/* first we count slots */

	rcu_read_lock();

	list_for_each_entry_rcu(info, &root->fs_info->space_info, list)

		slot_count++;

	rcu_read_unlock();



	/* space_slots == 0 means they are asking for a count */

	if (space_args.space_slots == 0) {

		space_args.total_spaces = slot_count;

		goto out;

	}

	alloc_size = sizeof(*dest) * slot_count;

	/* we generally have at most 6 or so space infos, one for each raid

	 * level.  So, a whole page should be more than enough for everyone

	 */

	if (alloc_size > PAGE_CACHE_SIZE)

		return -ENOMEM;



	space_args.total_spaces = 0;

	dest = (struct btrfs_ioctl_space_info *)

		(arg + sizeof(struct btrfs_ioctl_space_args));

	dest = kmalloc(alloc_size, GFP_NOFS);

	if (!dest)

		return -ENOMEM;

	dest_orig = dest;



	/* now we have a buffer to copy into */

	rcu_read_lock();

	list_for_each_entry_rcu(info, &root->fs_info->space_info, list) {

		if (!space_args.space_slots) {

			space_args.total_spaces++;

			continue;

		}

		/* make sure we don't copy more than we allocated

		 * in our buffer

		 */

		if (slot_count == 0)

			break;

		slot_count--;



		/* make sure userland has enough room in their buffer */

		if (space_args.total_spaces >= space_args.space_slots)

			break;



		space.flags = info->flags;

		space.total_bytes = info->total_bytes;

		space.used_bytes = info->bytes_used;

		if (copy_to_user(dest, &space, sizeof(space))) {

			ret = -EFAULT;

			break;

		}

		memcpy(dest, &space, sizeof(space));

		dest++;

		space_args.total_spaces++;

	}

	rcu_read_unlock();



	if (copy_to_user(arg, &space_args, sizeof(space_args)))

	user_dest = (struct btrfs_ioctl_space_info *)

		(arg + sizeof(struct btrfs_ioctl_space_args));



	if (copy_to_user(user_dest, dest_orig, alloc_size))

		ret = -EFAULT;



	kfree(dest_orig);

out:

	if (ret == 0 && copy_to_user(arg, &space_args, sizeof(space_args)))

		ret = -EFAULT;



	return ret;