Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935131AbcCKIbu (ORCPT ); Fri, 11 Mar 2016 03:31:50 -0500 Received: from mx1.redhat.com ([209.132.183.28]:48403 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934717AbcCKIbm (ORCPT ); Fri, 11 Mar 2016 03:31:42 -0500 Date: Fri, 11 Mar 2016 16:31:33 +0800 From: Baoquan He To: Dave Young Cc: Andrew Morton , linux-kernel@vger.kernel.org, d.hatayama@jp.fujitsu.com, vgoyal@redhat.com, kexec@lists.infradead.org, nasa4836@gmail.com Subject: Re: [PATCH] proc-vmcore: wrong data type casting fix Message-ID: <20160311083133.GA3207@x1.redhat.com> References: <20160311081501.GA9147@dhcp-128-65.nay.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160311081501.GA9147@dhcp-128-65.nay.redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Fri, 11 Mar 2016 08:31:41 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1900 Lines: 48 On 03/11/16 at 04:15pm, Dave Young wrote: > On i686 PAE enabled machine the contiguous physical area could be large > and it can cause triming down variables in below calculation in > read_vmcore() and mmap_vmcore(): > > tsz = min_t(size_t, m->offset + m->size - *fpos, buflen); > > Then the real size passed down is not correct any more. > Suppose m->offset + m->size - *fpos being truncated to 0, buflen >0 then > we will get tsz = 0. It is of course not an expected result. > > During out test there are two problems caused by it: ~ our > 1) read_vmcore will refuse to continue so makedumpfile fails. > 2) mmap_vmcore will trigger BUG_ON() in remap_pfn_range(). > > Use unsigned long long in min_t instead so that the variables are not > truncated. > > Signed-off-by: Baoquan He > Signed-off-by: Dave Young > --- > fs/proc/vmcore.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > --- linux-x86.orig/fs/proc/vmcore.c > +++ linux-x86/fs/proc/vmcore.c > @@ -231,7 +231,9 @@ static ssize_t __read_vmcore(char *buffe > > list_for_each_entry(m, &vmcore_list, list) { > if (*fpos < m->offset + m->size) { > - tsz = min_t(size_t, m->offset + m->size - *fpos, buflen); > + tsz = (size_t)min_t(unsigned long long, > + m->offset + m->size - *fpos, > + buflen); > start = m->paddr + *fpos - m->offset; > tmp = read_from_oldmem(buffer, tsz, &start, userbuf); > if (tmp < 0) > @@ -461,7 +463,8 @@ static int mmap_vmcore(struct file *file > if (start < m->offset + m->size) { > u64 paddr = 0; > > - tsz = min_t(size_t, m->offset + m->size - start, size); > + tsz = (size_t)min_t(unsigned long long, > + m->offset + m->size - start, size); > paddr = m->paddr + start - m->offset; > if (vmcore_remap_oldmem_pfn(vma, vma->vm_start + len, > paddr >> PAGE_SHIFT, tsz,