From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:58194 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387409AbeIXSe0 (ORCPT ); Mon, 24 Sep 2018 14:34:26 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jiang Biao , Thomas Gleixner , dave.hansen@linux.intel.com, luto@kernel.org, hpa@zytor.com, albcamus@gmail.com, zhong.weidong@zte.com.cn, Sasha Levin Subject: [PATCH 4.18 094/235] x86/pti: Check the return value of pti_user_pagetable_walk_p4d() Date: Mon, 24 Sep 2018 13:51:20 +0200 Message-Id: <20180924113114.607363781@linuxfoundation.org> In-Reply-To: <20180924113103.999624566@linuxfoundation.org> References: <20180924113103.999624566@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: 4.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jiang Biao [ Upstream commit b2b7d986a89b6c94b1331a909de1217214fb08c1 ] pti_user_pagetable_walk_p4d() can return NULL, so the return value should be checked to prevent a NULL pointer dereference. Add the check and a warning when the P4D allocation fails. Signed-off-by: Jiang Biao Signed-off-by: Thomas Gleixner Cc: dave.hansen@linux.intel.com Cc: luto@kernel.org Cc: hpa@zytor.com Cc: albcamus@gmail.com Cc: zhong.weidong@zte.com.cn Link: https://lkml.kernel.org/r/1532045192-49622-1-git-send-email-jiang.biao2@zte.com.cn Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- arch/x86/mm/pti.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) --- a/arch/x86/mm/pti.c +++ b/arch/x86/mm/pti.c @@ -177,7 +177,7 @@ static p4d_t *pti_user_pagetable_walk_p4 if (pgd_none(*pgd)) { unsigned long new_p4d_page = __get_free_page(gfp); - if (!new_p4d_page) + if (WARN_ON_ONCE(!new_p4d_page)) return NULL; set_pgd(pgd, __pgd(_KERNPG_TABLE | __pa(new_p4d_page))); @@ -196,9 +196,13 @@ static p4d_t *pti_user_pagetable_walk_p4 static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address) { gfp_t gfp = (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO); - p4d_t *p4d = pti_user_pagetable_walk_p4d(address); + p4d_t *p4d; pud_t *pud; + p4d = pti_user_pagetable_walk_p4d(address); + if (!p4d) + return NULL; + BUILD_BUG_ON(p4d_large(*p4d) != 0); if (p4d_none(*p4d)) { unsigned long new_pud_page = __get_free_page(gfp); @@ -355,6 +359,9 @@ static void __init pti_clone_p4d(unsigne pgd_t *kernel_pgd; user_p4d = pti_user_pagetable_walk_p4d(addr); + if (!user_p4d) + return; + kernel_pgd = pgd_offset_k(addr); kernel_p4d = p4d_offset(kernel_pgd, addr); *user_p4d = *kernel_p4d;