From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:34448 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755258AbdJPQRh (ORCPT ); Mon, 16 Oct 2017 12:17:37 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vitaly Mayatskikh , Al Viro Subject: [PATCH 4.9 30/39] fix unbalanced page refcounting in bio_map_user_iov Date: Mon, 16 Oct 2017 18:16:26 +0200 Message-Id: <20171016161432.198765175@linuxfoundation.org> In-Reply-To: <20171016161429.968555175@linuxfoundation.org> References: <20171016161429.968555175@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vitaly Mayatskikh commit 95d78c28b5a85bacbc29b8dba7c04babb9b0d467 upstream. 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 Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman --- block/bio.c | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/block/bio.c +++ b/block/bio.c @@ -1318,6 +1318,7 @@ struct bio *bio_map_user_iov(struct requ 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; @@ -1332,6 +1333,13 @@ struct bio *bio_map_user_iov(struct requ 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; }