staging: erofs: add two missing erofs_workgroup_put for corrupted images

As reported by erofs-utils fuzzer, these error handling
path will be entered to handle corrupted images.

Lack of erofs_workgroup_puts will cause unmounting
unsuccessfully.

Fix these return values to EFSCORRUPTED as well.

Fixes: 3883a79a ("staging: erofs: introduce VLE decompression support")
Cc: <stable@vger.kernel.org> # 4.19+
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Link: https://lore.kernel.org/r/20190819103426.87579-4-gaoxiang25@huawei.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/erofs/zdata.c

@@ -357,14 +357,16 @@ static struct z_erofs_collection *cllookup(struct z_erofs_collector *clt,
 	cl = z_erofs_primarycollection(pcl);
 	if (unlikely(cl->pageofs != (map->m_la & ~PAGE_MASK))) {
 		DBG_BUGON(1);
-		return ERR_PTR(-EIO);
+		erofs_workgroup_put(grp);
+		return ERR_PTR(-EFSCORRUPTED);
 	}
 
 	length = READ_ONCE(pcl->length);
 	if (length & Z_EROFS_PCLUSTER_FULL_LENGTH) {
 		if ((map->m_llen << Z_EROFS_PCLUSTER_LENGTH_BIT) > length) {
 			DBG_BUGON(1);
-			return ERR_PTR(-EIO);
+			erofs_workgroup_put(grp);
+			return ERR_PTR(-EFSCORRUPTED);
 		}
 	} else {
 		unsigned int llen = map->m_llen << Z_EROFS_PCLUSTER_LENGTH_BIT;