From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756929Ab3AYK4y (ORCPT ); Fri, 25 Jan 2013 05:56:54 -0500 Received: from e28smtp01.in.ibm.com ([122.248.162.1]:56453 "EHLO e28smtp01.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756597Ab3AYK4s (ORCPT ); Fri, 25 Jan 2013 05:56:48 -0500 From: Guo Chao To: axboe@kernel.dk Cc: linux-kernel@vger.kernel.org Subject: [PATCH 7/7] loopdev: ignore negative offset when calculate loop device size Date: Fri, 25 Jan 2013 18:56:22 +0800 Message-Id: <1359111382-12654-8-git-send-email-yan@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1359111382-12654-1-git-send-email-yan@linux.vnet.ibm.com> References: <1359111382-12654-1-git-send-email-yan@linux.vnet.ibm.com> X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13012510-4790-0000-0000-000006A21546 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Negative offset may cause loop device size larger than backing file size. $ fallocate -l 1M a $ losetup --offset 0xffffffffffff0000 /dev/loop0 a $ blockdev --getsize64 /dev/loop0 1114112 $ ls -l a -rw-r--r-- 1 root root 1048576 Jan 23 12:46 a $ cat /dev/loop0 cat: /dev/loop0: Input/output error It makes no sense to do that. Only apply offset when it's positive. Fix a typo in the comment by the way. Signed-off-by: Guo Chao --- drivers/block/loop.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 9190a82..7a235db 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -162,12 +162,13 @@ static struct loop_func_table *xfer_funcs[MAX_LO_CRYPT] = { static loff_t get_size(loff_t offset, loff_t sizelimit, struct file *file) { - loff_t size, loopsize; + loff_t loopsize; /* Compute loopsize in bytes */ - size = i_size_read(file->f_mapping->host); - loopsize = size - offset; - /* offset is beyond i_size, wierd but possible */ + loopsize = i_size_read(file->f_mapping->host); + if (offset > 0) + loopsize -= offset; + /* offset is beyond i_size, weird but possible */ if (loopsize < 0) return 0; -- 1.7.9.5