From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D27DDC64EB0 for ; Tue, 9 Oct 2018 07:04:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 856032075C for ; Tue, 9 Oct 2018 07:04:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 856032075C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zytor.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726568AbeJIOTk (ORCPT ); Tue, 9 Oct 2018 10:19:40 -0400 Received: from terminus.zytor.com ([198.137.202.136]:44507 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725835AbeJIOTk (ORCPT ); Tue, 9 Oct 2018 10:19:40 -0400 Received: from terminus.zytor.com (localhost [127.0.0.1]) by terminus.zytor.com (8.15.2/8.15.2) with ESMTPS id w9973dHL935844 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Tue, 9 Oct 2018 00:03:39 -0700 Received: (from tipbot@localhost) by terminus.zytor.com (8.15.2/8.15.2/Submit) id w9973dW5935841; Tue, 9 Oct 2018 00:03:39 -0700 Date: Tue, 9 Oct 2018 00:03:39 -0700 X-Authentication-Warning: terminus.zytor.com: tipbot set sender to tipbot@zytor.com using -f From: tip-bot for Kees Cook Message-ID: Cc: peterz@infradead.org, luto@kernel.org, mingo@kernel.org, tglx@linutronix.de, arnd@arndb.de, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, toshi.kani@hpe.com, torvalds@linux-foundation.org, bp@alien8.de, jroedel@suse.de, keescook@chromium.org, hpa@zytor.com, dave.hansen@linux.intel.com Reply-To: jroedel@suse.de, bp@alien8.de, torvalds@linux-foundation.org, toshi.kani@hpe.com, dave.hansen@linux.intel.com, hpa@zytor.com, keescook@chromium.org, mingo@kernel.org, luto@kernel.org, peterz@infradead.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, tglx@linutronix.de, arnd@arndb.de In-Reply-To: <20181008235434.GA35035@beast> References: <20181008235434.GA35035@beast> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/urgent] x86/mm: Avoid VLA in pgd_alloc() Git-Commit-ID: 184d47f0fd365108bd06ab26cdb3450b716269fd X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 184d47f0fd365108bd06ab26cdb3450b716269fd Gitweb: https://git.kernel.org/tip/184d47f0fd365108bd06ab26cdb3450b716269fd Author: Kees Cook AuthorDate: Mon, 8 Oct 2018 16:54:34 -0700 Committer: Ingo Molnar CommitDate: Tue, 9 Oct 2018 08:55:07 +0200 x86/mm: Avoid VLA in pgd_alloc() Arnd Bergmann reported that turning on -Wvla found a new (unintended) VLA usage: arch/x86/mm/pgtable.c: In function 'pgd_alloc': include/linux/build_bug.h:29:45: error: ISO C90 forbids variable length array 'u_pmds' [-Werror=vla] arch/x86/mm/pgtable.c:190:34: note: in expansion of macro 'static_cpu_has' #define PREALLOCATED_USER_PMDS (static_cpu_has(X86_FEATURE_PTI) ? \ ^~~~~~~~~~~~~~ arch/x86/mm/pgtable.c:431:16: note: in expansion of macro 'PREALLOCATED_USER_PMDS' pmd_t *u_pmds[PREALLOCATED_USER_PMDS]; ^~~~~~~~~~~~~~~~~~~~~~ Use the actual size of the array that is used for X86_FEATURE_PTI, which is known at build time, instead of the variable size. [ mingo: Squashed original fix with followup fix to avoid bisection breakage, wrote new changelog. ] Reported-by: Arnd Bergmann Original-written-by: Arnd Bergmann Reported-by: Borislav Petkov Signed-off-by: Kees Cook Cc: Andrew Morton Cc: Andy Lutomirski Cc: Arnd Bergmann Cc: Dave Hansen Cc: Joerg Roedel Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Toshi Kani Fixes: 1be3f247c288 ("x86/mm: Avoid VLA in pgd_alloc()") Link: http://lkml.kernel.org/r/20181008235434.GA35035@beast Signed-off-by: Ingo Molnar --- arch/x86/mm/pgtable.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c index 089e78c4effd..59274e2c1ac4 100644 --- a/arch/x86/mm/pgtable.c +++ b/arch/x86/mm/pgtable.c @@ -115,6 +115,8 @@ static inline void pgd_list_del(pgd_t *pgd) #define UNSHARED_PTRS_PER_PGD \ (SHARED_KERNEL_PMD ? KERNEL_PGD_BOUNDARY : PTRS_PER_PGD) +#define MAX_UNSHARED_PTRS_PER_PGD \ + max_t(size_t, KERNEL_PGD_BOUNDARY, PTRS_PER_PGD) static void pgd_set_mm(pgd_t *pgd, struct mm_struct *mm) @@ -181,6 +183,7 @@ static void pgd_dtor(pgd_t *pgd) * and initialize the kernel pmds here. */ #define PREALLOCATED_PMDS UNSHARED_PTRS_PER_PGD +#define MAX_PREALLOCATED_PMDS MAX_UNSHARED_PTRS_PER_PGD /* * We allocate separate PMDs for the kernel part of the user page-table @@ -189,6 +192,7 @@ static void pgd_dtor(pgd_t *pgd) */ #define PREALLOCATED_USER_PMDS (static_cpu_has(X86_FEATURE_PTI) ? \ KERNEL_PGD_PTRS : 0) +#define MAX_PREALLOCATED_USER_PMDS KERNEL_PGD_PTRS void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmd) { @@ -210,7 +214,9 @@ void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmd) /* No need to prepopulate any pagetable entries in non-PAE modes. */ #define PREALLOCATED_PMDS 0 +#define MAX_PREALLOCATED_PMDS 0 #define PREALLOCATED_USER_PMDS 0 +#define MAX_PREALLOCATED_USER_PMDS 0 #endif /* CONFIG_X86_PAE */ static void free_pmds(struct mm_struct *mm, pmd_t *pmds[], int count) @@ -428,8 +434,8 @@ static inline void _pgd_free(pgd_t *pgd) pgd_t *pgd_alloc(struct mm_struct *mm) { pgd_t *pgd; - pmd_t *u_pmds[PREALLOCATED_USER_PMDS]; - pmd_t *pmds[PREALLOCATED_PMDS]; + pmd_t *u_pmds[MAX_PREALLOCATED_USER_PMDS]; + pmd_t *pmds[MAX_PREALLOCATED_PMDS]; pgd = _pgd_alloc();