From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753216AbdJCMY6 (ORCPT ); Tue, 3 Oct 2017 08:24:58 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:33094 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752215AbdJCMYx (ORCPT ); Tue, 3 Oct 2017 08:24:53 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Marco Felsch , John Ogness , Andy Lutomirski , Tycho Andersen , Kees Cook , Peter Zijlstra , Brian Gerst , Tetsuo Handa , Borislav Petkov , Al Viro , Linux API , Andrew Morton , Linus Torvalds , Thomas Gleixner Subject: [PATCH 4.9 03/64] fs/proc: Report eip/esp in /prod/PID/stat for coredumping Date: Tue, 3 Oct 2017 14:22:55 +0200 Message-Id: <20171003114229.063264000@linuxfoundation.org> X-Mailer: git-send-email 2.14.2 In-Reply-To: <20171003114228.884821129@linuxfoundation.org> References: <20171003114228.884821129@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: John Ogness commit fd7d56270b526ca3ed0c224362e3c64a0f86687a upstream. Commit 0a1eb2d474ed ("fs/proc: Stop reporting eip and esp in /proc/PID/stat") stopped reporting eip/esp because it is racy and dangerous for executing tasks. The comment adds: As far as I know, there are no use programs that make any material use of these fields, so just get rid of them. However, existing userspace core-dump-handler applications (for example, minicoredumper) are using these fields since they provide an excellent cross-platform interface to these valuable pointers. So that commit introduced a user space visible regression. Partially revert the change and make the readout possible for tasks with the proper permissions and only if the target task has the PF_DUMPCORE flag set. Fixes: 0a1eb2d474ed ("fs/proc: Stop reporting eip and esp in> /proc/PID/stat") Reported-by: Marco Felsch Signed-off-by: John Ogness Reviewed-by: Andy Lutomirski Cc: Tycho Andersen Cc: Kees Cook Cc: Peter Zijlstra Cc: Brian Gerst Cc: Tetsuo Handa Cc: Borislav Petkov Cc: Al Viro Cc: Linux API Cc: Andrew Morton Cc: Linus Torvalds Link: http://lkml.kernel.org/r/87poatfwg6.fsf@linutronix.de Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman --- fs/proc/array.c | 9 +++++++++ 1 file changed, 9 insertions(+) --- a/fs/proc/array.c +++ b/fs/proc/array.c @@ -60,6 +60,7 @@ #include #include #include +#include #include #include #include @@ -416,7 +417,15 @@ static int do_task_stat(struct seq_file * esp and eip are intentionally zeroed out. There is no * non-racy way to read them without freezing the task. * Programs that need reliable values can use ptrace(2). + * + * The only exception is if the task is core dumping because + * a program is not able to use ptrace(2) in that case. It is + * safe because the task has stopped executing permanently. */ + if (permitted && (task->flags & PF_DUMPCORE)) { + eip = KSTK_EIP(task); + esp = KSTK_ESP(task); + } } get_task_comm(tcomm, task);