Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756639Ab2K2BdX (ORCPT ); Wed, 28 Nov 2012 20:33:23 -0500 Received: from LGEMRELSE1Q.lge.com ([156.147.1.111]:61180 "EHLO LGEMRELSE1Q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756296Ab2K2BdW (ORCPT ); Wed, 28 Nov 2012 20:33:22 -0500 X-AuditID: 9c93016f-b7b86ae000003a75-d1-50b6bb601c07 Date: Thu, 29 Nov 2012 10:33:20 +0900 From: Minchan Kim To: Nitin Gupta Cc: Greg KH , Seth Jennings , Dan Carpenter , Sam Hansen , Tomas M , Mihail Kasadjikov , Linux Driver Project , linux-kernel Subject: Re: [PATCH] zram: Prevent use of unmapped buffer Message-ID: <20121129013320.GA24077@blaptop> References: <1354001167-24878-1-git-send-email-ngupta@vflare.org> <20121128051505.GD23136@blaptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121128051505.GD23136@blaptop> User-Agent: Mutt/1.5.21 (2010-09-15) X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2181 Lines: 64 On Wed, Nov 28, 2012 at 02:15:05PM +0900, Minchan Kim wrote: > Hi Nitin, > > On Mon, Nov 26, 2012 at 11:26:07PM -0800, Nitin Gupta wrote: > > The commit c8f2f0db1 ("zram: Fix handling of incompressible pages") > > introduced a bug which caused a kunmap()'ed buffer to be used in case > > I got confused by the descripton. :( > The descripton is not right. > The problem is to access freed memory, not accessing to kunmaped buffer. > > partial I/O write. > > 1. uncmem = kmalloc > 2. zram_decompress_page(uncmem) > 3. memcpy(uncmem, user_mem) > 4. lzo1x_1_compress(uncmem) > 5. kfree(uncmem) > 6. src = uncmem > 7. memcpy(cmem, src, clen) <----- HIT > > > of partial writes where the data was found to be incompressible. > > I got it. You shouldn't mention partial write for proper description because it was usecase for swap-over-zram so it can't make partial write. Without partial write mention, your description is right but the problem I mentioned above is another problem for partial write so we need a another patch. I will cook. Thanks. > > This fixes bug 50081: > > https://bugzilla.kernel.org/show_bug.cgi?id=50081 > > > > Signed-off-by: Nitin Gupta > > Reported-by: Mihail Kasadjikov > > Reported-by: Tomas M > > Good catch! Shame on me. I should have reivewed more carefully. :( > Please resend it with revised descrption and title. > I will rebase mh patchset just sent on top of this bug fix patch. > > P.S) Sigh, Now code isn't clean due to partial read/write path handling. > IMHO, sooner or later, we need refactoring. > > -- > Kind regards, > Minchan Kim > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/