From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752602AbcGNUZz (ORCPT ); Thu, 14 Jul 2016 16:25:55 -0400 Received: from mail.kernel.org ([198.145.29.136]:44752 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751375AbcGNUXG (ORCPT ); Thu, 14 Jul 2016 16:23:06 -0400 From: Andy Lutomirski To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, Brian Gerst , Borislav Petkov , Andy Lutomirski Subject: [PATCH 02/11] x86/cpa: In populate_pgd, don't set the pgd entry until it's populated Date: Thu, 14 Jul 2016 13:22:50 -0700 Message-Id: X-Mailer: git-send-email 2.7.4 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This avoids pointless races in which another CPU or task might see a partially populated global pgd entry. These races should normally be harmless, but, if another CPU propagates the entry via vmalloc_fault and then populate_pgd fails (due to memory allocation failure, for example), this prevents a use-after-free of the pgd entry. Signed-off-by: Andy Lutomirski --- arch/x86/mm/pageattr.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 7a1f7bbf4105..6088aa03de63 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -1104,8 +1104,6 @@ static int populate_pgd(struct cpa_data *cpa, unsigned long addr) pud = (pud_t *)get_zeroed_page(GFP_KERNEL | __GFP_NOTRACK); if (!pud) return -1; - - set_pgd(pgd_entry, __pgd(__pa(pud) | _KERNPG_TABLE)); } pgprot_val(pgprot) &= ~pgprot_val(cpa->mask_clr); @@ -1113,11 +1111,16 @@ static int populate_pgd(struct cpa_data *cpa, unsigned long addr) ret = populate_pud(cpa, addr, pgd_entry, pgprot); if (ret < 0) { - unmap_pgd_range(cpa->pgd, addr, + if (pud) + free_page((unsigned long)pud); + unmap_pud_range(pgd_entry, addr, addr + (cpa->numpages << PAGE_SHIFT)); return ret; } + if (pud) + set_pgd(pgd_entry, __pgd(__pa(pud) | _KERNPG_TABLE)); + cpa->numpages = ret; return 0; } -- 2.7.4