From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Lutomirski Subject: [PATCH v4 04/29] x86/cpa: In populate_pgd, don't set the pgd entry until it's populated Date: Sun, 26 Jun 2016 14:55:26 -0700 Message-ID: References: Return-path: Received: from mail.kernel.org ([198.145.29.136]:59466 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751661AbcFZV4D (ORCPT ); Sun, 26 Jun 2016 17:56:03 -0400 In-Reply-To: In-Reply-To: References: Sender: linux-arch-owner@vger.kernel.org List-ID: To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, Borislav Petkov , Nadav Amit , Kees Cook , Brian Gerst , "kernel-hardening@lists.openwall.com" , Linus Torvalds , Josh Poimboeuf , Jann Horn , Heiko Carstens , Andy Lutomirski 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 | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 7a1f7bbf4105..6a8026918bf6 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -1113,7 +1113,9 @@ 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; } -- 2.7.4