From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932464AbdGSK0j (ORCPT ); Wed, 19 Jul 2017 06:26:39 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:42822 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932230AbdGSK0g (ORCPT ); Wed, 19 Jul 2017 06:26:36 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Kees Cook , Linus Torvalds Subject: [PATCH 4.9 46/72] exec: Limit arg stack to at most 75% of _STK_LIM Date: Wed, 19 Jul 2017 12:24:40 +0200 Message-Id: <20170719102443.307375921@linuxfoundation.org> X-Mailer: git-send-email 2.13.3 In-Reply-To: <20170719102435.760649060@linuxfoundation.org> References: <20170719102435.760649060@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: Kees Cook commit da029c11e6b12f321f36dac8771e833b65cec962 upstream. To avoid pathological stack usage or the need to special-case setuid execs, just limit all arg stack usage to at most 75% of _STK_LIM (6MB). Signed-off-by: Kees Cook Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- fs/exec.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) --- a/fs/exec.c +++ b/fs/exec.c @@ -215,8 +215,7 @@ static struct page *get_arg_page(struct if (write) { unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start; - unsigned long ptr_size; - struct rlimit *rlim; + unsigned long ptr_size, limit; /* * Since the stack will hold pointers to the strings, we @@ -245,14 +244,16 @@ static struct page *get_arg_page(struct return page; /* - * Limit to 1/4-th the stack size for the argv+env strings. + * Limit to 1/4 of the max stack size or 3/4 of _STK_LIM + * (whichever is smaller) for the argv+env strings. * This ensures that: * - the remaining binfmt code will not run out of stack space, * - the program will have a reasonable amount of stack left * to work from. */ - rlim = current->signal->rlim; - if (size > READ_ONCE(rlim[RLIMIT_STACK].rlim_cur) / 4) + limit = _STK_LIM / 4 * 3; + limit = min(limit, rlimit(RLIMIT_STACK) / 4); + if (size > limit) goto fail; }