Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751830AbdIVFSn (ORCPT ); Fri, 22 Sep 2017 01:18:43 -0400 Received: from mail-qt0-f193.google.com ([209.85.216.193]:38395 "EHLO mail-qt0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750839AbdIVFSm (ORCPT ); Fri, 22 Sep 2017 01:18:42 -0400 X-Google-Smtp-Source: AOwi7QB++M9r2BLhdimjQnHHnwLwOzGfxDcRYlknX0DjHqvOUZlrTOLi8Wb7VNZBG6XvAr5ZJl+vPQ== Date: Fri, 22 Sep 2017 01:18:39 -0400 Message-ID: <87bmm3xqds.wl-v.mayatskih@gmail.com> From: Vitaly Mayatskikh To: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Jens Axboe Subject: [PATCH] fix unbalanced page refcounting in bio_map_user_iov User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/25.3 Mule/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1002 Lines: 36 bio_map_user_iov and bio_unmap_user do unbalanced pages refcounting if IO vector has small consecutive buffers belonging to the same page. bio_add_pc_page merges them into one, but the page reference is never dropped. Signed-off-by: Vitaly Mayatskikh diff --git a/block/bio.c b/block/bio.c index b38e962fa83e..10cd3b6bed27 100644 --- a/block/bio.c +++ b/block/bio.c @@ -1383,6 +1383,7 @@ struct bio *bio_map_user_iov(struct request_queue *q, offset = offset_in_page(uaddr); for (j = cur_page; j < page_limit; j++) { unsigned int bytes = PAGE_SIZE - offset; + unsigned short prev_bi_vcnt = bio->bi_vcnt; if (len <= 0) break; @@ -1397,6 +1398,13 @@ struct bio *bio_map_user_iov(struct request_queue *q, bytes) break; + /* + * check if vector was merged with previous + * drop page reference if needed + */ + if (bio->bi_vcnt == prev_bi_vcnt) + put_page(pages[j]); + len -= bytes; offset = 0; } -- wbr, Vitaly