From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423034AbcFMSjl (ORCPT ); Mon, 13 Jun 2016 14:39:41 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:43808 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161435AbcFMShh (ORCPT ); Mon, 13 Jun 2016 14:37:37 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Emese Revfy" , "Jarod Wilson" , "Cyrill Gorcunov" , "Al Viro" , "Mathias Krause" , "Mateusz Guzik" , "Linus Torvalds" , "Pax Team" , "Alexey Dobriyan" Date: Mon, 13 Jun 2016 19:36:37 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 078/114] proc: prevent accessing /proc//environ until it's ready In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.36-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Mathias Krause commit 8148a73c9901a8794a50f950083c00ccf97d43b3 upstream. If /proc//environ gets read before the envp[] array is fully set up in create_{aout,elf,elf_fdpic,flat}_tables(), we might end up trying to read more bytes than are actually written, as env_start will already be set but env_end will still be zero, making the range calculation underflow, allowing to read beyond the end of what has been written. Fix this as it is done for /proc//cmdline by testing env_end for zero. It is, apparently, intentionally set last in create_*_tables(). This bug was found by the PaX size_overflow plugin that detected the arithmetic underflow of 'this_len = env_end - (env_start + src)' when env_end is still zero. The expected consequence is that userland trying to access /proc//environ of a not yet fully set up process may get inconsistent data as we're in the middle of copying in the environment variables. Fixes: https://forums.grsecurity.net/viewtopic.php?f=3&t=4363 Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=116461 Signed-off-by: Mathias Krause Cc: Emese Revfy Cc: Pax Team Cc: Al Viro Cc: Mateusz Guzik Cc: Alexey Dobriyan Cc: Cyrill Gorcunov Cc: Jarod Wilson Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Ben Hutchings --- fs/proc/base.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -809,7 +809,8 @@ static ssize_t environ_read(struct file int ret = 0; struct mm_struct *mm = file->private_data; - if (!mm) + /* Ensure the process spawned far enough to have an environment. */ + if (!mm || !mm->env_end) return 0; page = (char *)__get_free_page(GFP_TEMPORARY);