Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754060AbdFSSjA (ORCPT + 2 others); Mon, 19 Jun 2017 14:39:00 -0400 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:52682 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753992AbdFSSi5 (ORCPT ); Mon, 19 Jun 2017 14:38:57 -0400 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux@roeck-us.net Cc: Thomas Gleixner , Peter Zijlstra , Mathias Krause , Willy Tarreau Subject: [PATCH 3.10 231/268] x86/vdso: Plug race between mapping and ELF header setup Date: Mon, 19 Jun 2017 20:32:10 +0200 Message-Id: <1497897167-14556-232-git-send-email-w@1wt.eu> X-Mailer: git-send-email 2.8.0.rc2.1.gbe9624a In-Reply-To: <1497897167-14556-1-git-send-email-w@1wt.eu> References: <1497897167-14556-1-git-send-email-w@1wt.eu> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: From: Thomas Gleixner commit 6fdc6dd90272ce7e75d744f71535cfbd8d77da81 upstream. 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 Link: http://lkml.kernel.org/r/20170410151723.602367196@linutronix.de Signed-off-by: Thomas Gleixner Signed-off-by: Willy Tarreau --- 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 01f15b2..2fa7f4f 100644 --- a/arch/x86/include/asm/elf.h +++ b/arch/x86/include/asm/elf.h @@ -272,7 +272,7 @@ struct task_struct; #define ARCH_DLINFO_IA32(vdso_enabled) \ do { \ - if (vdso_enabled) { \ + if (VDSO_CURRENT_BASE) { \ NEW_AUX_ENT(AT_SYSINFO, VDSO_ENTRY); \ NEW_AUX_ENT(AT_SYSINFO_EHDR, VDSO_CURRENT_BASE); \ } \ -- 2.8.0.rc2.1.gbe9624a