Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753672AbdDJR6l (ORCPT ); Mon, 10 Apr 2017 13:58:41 -0400 Received: from terminus.zytor.com ([65.50.211.136]:51389 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753233AbdDJQjv (ORCPT ); Mon, 10 Apr 2017 12:39:51 -0400 Date: Mon, 10 Apr 2017 09:34:32 -0700 From: tip-bot for Thomas Gleixner Message-ID: Cc: linux-kernel@vger.kernel.org, peterz@infradead.org, minipli@googlemail.com, hpa@zytor.com, luto@amacapital.net, tglx@linutronix.de, mingo@kernel.org Reply-To: linux-kernel@vger.kernel.org, minipli@googlemail.com, peterz@infradead.org, hpa@zytor.com, luto@amacapital.net, tglx@linutronix.de, mingo@kernel.org In-Reply-To: <20170410151723.602367196@linutronix.de> References: <20170410151723.602367196@linutronix.de> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/urgent] x86/vdso: Plug race between mapping and ELF header setup Git-Commit-ID: 6fdc6dd90272ce7e75d744f71535cfbd8d77da81 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 List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1775 Lines: 50 Commit-ID: 6fdc6dd90272ce7e75d744f71535cfbd8d77da81 Gitweb: http://git.kernel.org/tip/6fdc6dd90272ce7e75d744f71535cfbd8d77da81 Author: Thomas Gleixner AuthorDate: Mon, 10 Apr 2017 17:14:28 +0200 Committer: Thomas Gleixner CommitDate: Mon, 10 Apr 2017 18:31:41 +0200 x86/vdso: Plug race between mapping and ELF header setup The vsyscall32 sysctl can racy against a concurrent fork when it switches from disabled to enabled: arch_setup_additional_pages() if (vdso32_enabled) --> No mapping sysctl.vsysscall32() --> vdso32_enabled = true create_elf_tables() ARCH_DLINFO_IA32 if (vdso32_enabled) { --> Add VDSO entry with NULL pointer Make ARCH_DLINFO_IA32 check whether the VDSO mapping has been set up for the newly forked process or not. Signed-off-by: Thomas Gleixner Acked-by: Andy Lutomirski Cc: Peter Zijlstra Cc: Mathias Krause Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/20170410151723.602367196@linutronix.de Signed-off-by: Thomas Gleixner --- arch/x86/include/asm/elf.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h index 9d49c18..3762536 100644 --- a/arch/x86/include/asm/elf.h +++ b/arch/x86/include/asm/elf.h @@ -287,7 +287,7 @@ struct task_struct; #define ARCH_DLINFO_IA32 \ do { \ - if (vdso32_enabled) { \ + if (VDSO_CURRENT_BASE) { \ NEW_AUX_ENT(AT_SYSINFO, VDSO_ENTRY); \ NEW_AUX_ENT(AT_SYSINFO_EHDR, VDSO_CURRENT_BASE); \ } \