From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751529AbcHLH1C (ORCPT ); Fri, 12 Aug 2016 03:27:02 -0400 Received: from mail-wm0-f68.google.com ([74.125.82.68]:35312 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750878AbcHLH1B (ORCPT ); Fri, 12 Aug 2016 03:27:01 -0400 Date: Fri, 12 Aug 2016 08:26:51 +0100 From: Salah Triki To: Luis de Bethencourt Cc: Salah Triki , 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 Message-ID: <20160812072651.GA6033@pc> References: <8f7f9b76ead677bdc834867e549ea6c4d1c04ccd.1470867071.git.salah.triki@gmail.com> <57AC59D0.7030408@osg.samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <57AC59D0.7030408@osg.samsung.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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