f2fs: avoid unneeded lookup when xattr name length is too long

In f2fs_setxattr we have limit this attribute name length, so we should also
check it in f2fs_getxattr to avoid useless lookup caused by invalid name length.
Signed-off-by: NChao Yu <chao2.yu@samsung.com>
Signed-off-by: NJaegeuk Kim <jaegeuk.kim@samsung.com>

fs/f2fs/xattr.c

@@ -407,6 +407,8 @@ int f2fs_getxattr(struct inode *inode, int name_index, const char *name,
 	if (name == NULL)
 		return -EINVAL;
 	name_len = strlen(name);
+	if (name_len > F2FS_NAME_LEN)
+		return -ERANGE;
 
 	base_addr = read_all_xattrs(inode, NULL);
 	if (!base_addr)