From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752458AbcHLJjZ (ORCPT ); Fri, 12 Aug 2016 05:39:25 -0400 Received: from ec2-52-27-115-49.us-west-2.compute.amazonaws.com ([52.27.115.49]:46128 "EHLO s-opensource.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751356AbcHLJjX (ORCPT ); Fri, 12 Aug 2016 05:39:23 -0400 Message-ID: <57AD9932.6050608@osg.samsung.com> Date: Fri, 12 Aug 2016 10:38:58 +0100 From: Luis de Bethencourt User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.8.0 MIME-Version: 1.0 To: Salah Triki CC: akpm@linux-foundation.org, viro@zeniv.linux.org.uk, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/4] befs: check allocation_group number before use References: <8f7f9b76ead677bdc834867e549ea6c4d1c04ccd.1470867071.git.salah.triki@gmail.com> <57AC59D0.7030408@osg.samsung.com> <20160812072651.GA6033@pc> In-Reply-To: <20160812072651.GA6033@pc> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/08/16 08:26, Salah Triki wrote: > On Thu, Aug 11, 2016 at 11:56:16AM +0100, Luis de Bethencourt wrote: >> On 10/08/16 23:12, Salah Triki wrote: >>> Check that the allocation group number is not greater or equal to the >>> number of allocations group in the file system and return BEF_ERR in the >>> case of error. >>> >>> Signed-off-by: Salah Triki >>> --- >>> fs/befs/befs.h | 5 +++++ >>> 1 file changed, 5 insertions(+) >>> >>> diff --git a/fs/befs/befs.h b/fs/befs/befs.h >>> index 55f3ea2..6daf4c4 100644 >>> --- a/fs/befs/befs.h >>> +++ b/fs/befs/befs.h >>> @@ -121,6 +121,11 @@ BEFS_I(const struct inode *inode) >>> static inline befs_blocknr_t >>> iaddr2blockno(struct super_block *sb, const befs_inode_addr *iaddr) >>> { >>> + if (iaddr->allocation_group >= BEFS_SB(sb)->num_ags) { >>> + befs_error(sb, "BEFS: Invalid allocation group %u, max is %u", >>> + iaddr->allocation_group, BEFS_SB(sb)->num_ags); >>> + return BEFS_ERR; >>> + } >>> return ((iaddr->allocation_group << BEFS_SB(sb)->ag_shift) + >>> iaddr->start); >>> } >>> >> >> Hi Salah, >> >> To understand why would we check for this. When can this error happen? I mean, >> when can iaddr2blockno() be called with an out of bounds allocation group? >> >> Thanks, >> Luis > > Hi Luis, > > allocation group number is set to blockno >> BEFS_SB(sb)->ag_shift by > blockno2iaddr(), so if ag_shift is not valid, an out of bound may occur. > By now, thanx to your question ;), I think it's better to check the validity > of ag_shift when the superblock is loaded. > > Nack. > > Thanx for the question :) > Salah > No problem :) I will assume the Nack covers patch 1 to 3. Since they are all related. Enjoy the weekend, Luis