From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754691AbZJ0NSs (ORCPT ); Tue, 27 Oct 2009 09:18:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754221AbZJ0NSs (ORCPT ); Tue, 27 Oct 2009 09:18:48 -0400 Received: from mx1.redhat.com ([209.132.183.28]:11979 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754156AbZJ0NSr (ORCPT ); Tue, 27 Oct 2009 09:18:47 -0400 Date: Tue, 27 Oct 2009 09:17:51 -0400 From: Vivek Goyal To: Jiri Slaby Cc: mingo@redhat.com, tglx@linutronix.de, hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org, "Eric W. Biederman" , Simon Horman , Paul Mundt , Ingo Molnar Subject: Re: [PATCH v2 1/1] crash_dump: fix non-pae kdump kernel memory accesses Message-ID: <20091027131750.GA10513@redhat.com> References: <20091025162018.GB20391@elte.hu> <1256551903-30567-1-git-send-email-jirislaby@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1256551903-30567-1-git-send-email-jirislaby@gmail.com> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 26, 2009 at 11:11:43AM +0100, Jiri Slaby wrote: > Non-PAE 32-bit dump kernels may wrap an address around 4G and > poke unwanted space. ptes there are 32-bit long, and since > pfn << PAGE_SIZE may exceed this limit, high pfn bits are cropped > and wrong address mapped by kmap_atomic_pfn in copy_oldmem_page. > > Don't allow this behavior in non-PAE kdump kernels by checking > pfns passed into copy_oldmem_page. In the case of failure, > userspace process gets EFAULT. > > [v2] > - fix comments > - move ifdefs inside the function > > Signed-off-by: Jiri Slaby > Cc: Vivek Goyal > Cc: "Eric W. Biederman" > Cc: Simon Horman > Cc: Paul Mundt > Cc: Ingo Molnar > --- Looks good to me. Acked-by: Vivek Goyal Thanks Vivek > arch/x86/kernel/crash_dump_32.c | 19 +++++++++++++++++++ > 1 files changed, 19 insertions(+), 0 deletions(-) > > diff --git a/arch/x86/kernel/crash_dump_32.c b/arch/x86/kernel/crash_dump_32.c > index f7cdb3b..cd97ce1 100644 > --- a/arch/x86/kernel/crash_dump_32.c > +++ b/arch/x86/kernel/crash_dump_32.c > @@ -16,6 +16,22 @@ static void *kdump_buf_page; > /* Stores the physical address of elf header of crash image. */ > unsigned long long elfcorehdr_addr = ELFCORE_ADDR_MAX; > > +static inline bool is_crashed_pfn_valid(unsigned long pfn) > +{ > +#ifndef CONFIG_X86_PAE > + /* > + * non-PAE kdump kernel executed from a PAE one will crop high pte > + * bits and poke unwanted space counting again from address 0, we > + * don't want that. pte must fit into unsigned long. In fact the > + * test checks high 12 bits for being zero (pfn will be shifted left > + * by PAGE_SHIFT). > + */ > + return pte_pfn(pfn_pte(pfn, __pgprot(0))) == pfn; > +#else > + return true; > +#endif > +} > + > /** > * copy_oldmem_page - copy one page from "oldmem" > * @pfn: page frame number to be copied > @@ -41,6 +57,9 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf, > if (!csize) > return 0; > > + if (!is_crashed_pfn_valid(pfn)) > + return -EFAULT; > + > vaddr = kmap_atomic_pfn(pfn, KM_PTE0); > > if (!userbuf) { > -- > 1.6.4.2