From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755980AbcIQHfT (ORCPT ); Sat, 17 Sep 2016 03:35:19 -0400 Received: from mx2.suse.de ([195.135.220.15]:46840 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754047AbcIQHfL (ORCPT ); Sat, 17 Sep 2016 03:35:11 -0400 Date: Sat, 17 Sep 2016 09:35:11 +0200 From: Borislav Petkov To: Colin King Cc: Yazen Ghannam , linux-kernel@vger.kernel.org, Aravind Gopalakrishnan Subject: Re: [PATCH][V2][Fix commit message] x86/RAS/mce_amd_inj: fix signed wrap around when decrementing index i Message-ID: <20160917073511.GA29030@nazgul.tnic> References: <20160916112223.32398-1-colin.king@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20160916112223.32398-1-colin.king@canonical.com> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (drop peterz from CC). On Fri, Sep 16, 2016 at 12:22:23PM +0100, Colin King wrote: > From: Colin Ian King > > Integer index i needs to be a signed int rather than unsigned to avoid > a wrap-around when decrementing in the while loop. For example, if the Damn corner cases :-\ > debugfs_create_file fails when i is zero, the current situation will > predecrement i in the while loop, wrapping i to the maximum signed > integer and cause multiple out of bounds reads on dfs_fls[i].d as > the loop interates to zero. > > Also add (int) cast to fix warning that the original fix attempted > to fix. Thanks, that's a good catch! But, can we keep the unsigned-ness of i as it is an index and do this instead? (Oh, and make it return ENODEV - that ENOMEM is just plain wrong most of the time). --- diff --git a/arch/x86/ras/mce_amd_inj.c b/arch/x86/ras/mce_amd_inj.c index cd318d93099e..a2dafca467e6 100644 --- a/arch/x86/ras/mce_amd_inj.c +++ b/arch/x86/ras/mce_amd_inj.c @@ -457,8 +457,12 @@ static int __init init_mce_inject(void) &i_mce, dfs_fls[i].fops); - if (!dfs_fls[i].d) + if (!dfs_fls[i].d) { + if (!i) + return -ENODEV; + goto err_dfs_add; + } } return 0; @@ -470,7 +474,7 @@ err_dfs_add: debugfs_remove(dfs_inj); dfs_inj = NULL; - return -ENOMEM; + return -ENODEV; } static void __exit exit_mce_inject(void) -- Regards/Gruss, Boris. SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --