btrfs: tree_search, search_ioctl: accept varying buffer

rewrite search_ioctl to accept a buffer with varying size
Signed-off-by: Gerhard Heift <Gerhard@Heift.Name>
Signed-off-by: Chris Mason <clm@fb.com>
Acked-by: David Sterba <dsterba@suse.cz>

fs/btrfs/ioctl.c

@@ -1957,6 +1957,7 @@ static noinline int copy_to_sk(struct btrfs_root *root,
 			       struct btrfs_path *path,
 			       struct btrfs_key *key,
 			       struct btrfs_ioctl_search_key *sk,
+			       size_t buf_size,
 			       char *buf,
 			       unsigned long *sk_offset,
 			       int *num_found)
@@ -1989,11 +1990,10 @@ static noinline int copy_to_sk(struct btrfs_root *root,
 		if (!key_in_sk(key, sk))
 			continue;
 
-		if (sizeof(sh) + item_len > BTRFS_SEARCH_ARGS_BUFSIZE)
+		if (sizeof(sh) + item_len > buf_size)
 			item_len = 0;
 
-		if (sizeof(sh) + item_len + *sk_offset >
-		    BTRFS_SEARCH_ARGS_BUFSIZE) {
+		if (sizeof(sh) + item_len + *sk_offset > buf_size) {
 			ret = 1;
 			goto out;
 		}
@@ -2040,17 +2040,21 @@ static noinline int copy_to_sk(struct btrfs_root *root,
 }
 
 static noinline int search_ioctl(struct inode *inode,
-				 struct btrfs_ioctl_search_args *args)
+				 struct btrfs_ioctl_search_key *sk,
+				 size_t buf_size,
+				 char *buf)
 {
 	struct btrfs_root *root;
 	struct btrfs_key key;
 	struct btrfs_path *path;
-	struct btrfs_ioctl_search_key *sk = &args->key;
 	struct btrfs_fs_info *info = BTRFS_I(inode)->root->fs_info;
 	int ret;
 	int num_found = 0;
 	unsigned long sk_offset = 0;
 
+	if (buf_size < sizeof(struct btrfs_ioctl_search_header))
+		return -EOVERFLOW;
+
 	path = btrfs_alloc_path();
 	if (!path)
 		return -ENOMEM;
@@ -2084,7 +2088,7 @@ static noinline int search_ioctl(struct inode *inode,
 				ret = 0;
 			goto err;
 		}
-		ret = copy_to_sk(root, path, &key, sk, args->buf,
+		ret = copy_to_sk(root, path, &key, sk, buf_size, buf,
 				 &sk_offset, &num_found);
 		btrfs_release_path(path);
 		if (ret)
@@ -2113,7 +2117,7 @@ static noinline int btrfs_ioctl_tree_search(struct file *file,
 		return PTR_ERR(args);
 
 	inode = file_inode(file);
-	ret = search_ioctl(inode, args);
+	ret = search_ioctl(inode, &args->key, sizeof(args->buf), args->buf);
 	if (ret == 0 && copy_to_user(argp, args, sizeof(*args)))
 		ret = -EFAULT;
 	kfree(args);