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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS 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 A8858C43219 for ; Fri, 3 May 2019 18:12:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 85523204FD for ; Fri, 3 May 2019 18:12:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728643AbfECSMT (ORCPT ); Fri, 3 May 2019 14:12:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47294 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726992AbfECSMR (ORCPT ); Fri, 3 May 2019 14:12:17 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id DFCDC58E3E; Fri, 3 May 2019 18:12:16 +0000 (UTC) Received: from jsavitz.bos.com (dhcp-17-237.bos.redhat.com [10.18.17.237]) by smtp.corp.redhat.com (Postfix) with ESMTP id EA7AB60BFB; Fri, 3 May 2019 18:12:14 +0000 (UTC) From: Joel Savitz To: linux-kernel@vger.kernel.org Cc: Joel Savitz , Thomas Gleixner , Ingo Molnar , Masami Hiramatsu , Waiman Long , Mauro Carvalho Chehab , Kristina Martsenko , Andrew Morton , Cyrill Gorcunov , Kees Cook , "Gustavo A. R. Silva" , YueHaibing , Micah Morton , Yang Shi , Jann Horn , Alexey Dobriyan , Rafael Aquini , Michael Kerrisk , Yury Norov , David Laight Subject: [PATCH v3 1/2] kernel/sys: add PR_GET_TASK_SIZE option to prctl(2) Date: Fri, 3 May 2019 14:10:20 -0400 Message-Id: <1556907021-29730-2-git-send-email-jsavitz@redhat.com> In-Reply-To: <1556907021-29730-1-git-send-email-jsavitz@redhat.com> References: <1556907021-29730-1-git-send-email-jsavitz@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Fri, 03 May 2019 18:12:17 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When PR_GET_TASK_SIZE is passed to prctl, the kernel will attempt to copy the value of TASK_SIZE to the userspace address in arg2. It is important that we account for the case of the userspace task running in 32-bit compat mode on a 64-bit kernel. As such, we must be careful to copy the correct number of bytes to userspace to avoid stack corruption. Suggested-by: Yuri Norov Suggested-by: Alexey Dobriyan Signed-off-by: Joel Savitz --- include/uapi/linux/prctl.h | 3 +++ kernel/sys.c | 23 +++++++++++++++++++++++ 2 files changed, 26 insertions(+) diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index 094bb03b9cc2..2c261c461952 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -229,4 +229,7 @@ struct prctl_mm_map { # define PR_PAC_APDBKEY (1UL << 3) # define PR_PAC_APGAKEY (1UL << 4) +/* Get the process virtual memory size (i.e. the highest usable VM address) */ +#define PR_GET_TASK_SIZE 55 + #endif /* _LINUX_PRCTL_H */ diff --git a/kernel/sys.c b/kernel/sys.c index 12df0e5434b8..709584400070 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -2252,6 +2252,26 @@ static int propagate_has_child_subreaper(struct task_struct *p, void *data) return 1; } +static int prctl_get_tasksize(void __user *uaddr) +{ + unsigned long current_task_size, current_word_size; + + current_task_size = TASK_SIZE; + current_word_size = sizeof(unsigned long); + +#ifdef CONFIG_64BIT + /* On 64-bit architecture, we must check whether the current thread + * is running in 32-bit compat mode. If it is, we can simply cut + * the size in half. This avoids corruption of the userspace stack. + */ + if (test_thread_flag(TIF_ADDR32)) + current_word_size >>= 1; +#endif + + return copy_to_user(uaddr, ¤t_task_size, current_word_size) ? -EFAULT : 0; +} + int __weak arch_prctl_spec_ctrl_get(struct task_struct *t, unsigned long which) { return -EINVAL; @@ -2486,6 +2506,9 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, return -EINVAL; error = PAC_RESET_KEYS(me, arg2); break; + case PR_GET_TASK_SIZE: + error = prctl_get_tasksize((void *)arg2); + break; default: error = -EINVAL; break; -- 2.18.1