From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757191AbdDQBVH (ORCPT ); Sun, 16 Apr 2017 21:21:07 -0400 Received: from mail-pg0-f66.google.com ([74.125.83.66]:36488 "EHLO mail-pg0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757056AbdDQBVD (ORCPT ); Sun, 16 Apr 2017 21:21:03 -0400 Date: Mon, 17 Apr 2017 10:21:05 +0900 From: Sergey Senozhatsky To: Minchan Kim Cc: Sergey Senozhatsky , Andrew Morton , linux-kernel@vger.kernel.org, Sergey Senozhatsky , kernel-team@lge.com, stable@vger.kernel.org Subject: Re: [PATCH 1/3] zram: fix operator precedence to get offset Message-ID: <20170417012105.GA518@jagdpanzerIV.localdomain> References: <1492042622-12074-1-git-send-email-minchan@kernel.org> <20170414050747.GB462@jagdpanzerIV.localdomain> <20170414153251.GA16910@bgram> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170414153251.GA16910@bgram> User-Agent: Mutt/1.8.1 (2017-04-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On (04/15/17 00:33), Minchan Kim wrote: > On Fri, Apr 14, 2017 at 02:07:47PM +0900, Sergey Senozhatsky wrote: > > On (04/13/17 09:17), Minchan Kim wrote: > > [..] > > > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c > > > index 9e2199060040..83c38a123242 100644 > > > --- a/drivers/block/zram/zram_drv.c > > > +++ b/drivers/block/zram/zram_drv.c > > > @@ -930,7 +930,7 @@ static int zram_rw_page(struct block_device *bdev, sector_t sector, > > > } > > > > > > index = sector >> SECTORS_PER_PAGE_SHIFT; > > > - offset = sector & (SECTORS_PER_PAGE - 1) << SECTOR_SHIFT; > > > + offset = (sector & (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT; > > > > sorry, can it actually produce different results? > > I got your point. Actually, offset was wrong but rw_page is called > with PAGE_SIZE io while that offset is related to only partial io > (non-PAGEE size io). IOW, although the wrong offset it is never used > in functions. > > To find subtle corruption in ppc64, I added some debug code to > catch up wrong buffer overflow and found it with other bugs but > didn't prove the specific case is valid case or not. Good catch, Sergey! > > However, it should be *fixed* to prevent confusion in future but surely, > no need to go to the stable. I will send reply to Greg to prevent merging > it to *stable* when he send review asking to merge. cool. thanks! > And next week I will send another fix which *maybe* removes code to get the > offset in zram_rw_page. sounds interesting! -ss