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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 4A0B4C43219 for ; Sat, 27 Apr 2019 15:25:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 222FB206A3 for ; Sat, 27 Apr 2019 15:25:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728399AbfD0PZe (ORCPT ); Sat, 27 Apr 2019 11:25:34 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:33312 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727415AbfD0PPY (ORCPT ); Sat, 27 Apr 2019 11:15:24 -0400 Received: from [192.168.4.242] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1hKP2v-000144-St; Sat, 27 Apr 2019 16:15:22 +0100 Received: from ben by deadeye with local (Exim 4.92) (envelope-from ) id 1hKP2n-0004dg-Mi; Sat, 27 Apr 2019 16:15:13 +0100 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, Denis Kirjanov , "Oleg Nesterov" , "Hugh Dickins" , "Michal Hocko" , "Linus Torvalds" , "Larry Woodman" Date: Sat, 27 Apr 2019 16:13:09 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 180/202] mm/mmap.c: expand_downwards: don't require the gap if !vm_prev In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.242 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.66-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Oleg Nesterov commit 32e4e6d5cbb0c0e427391635991fe65e17797af8 upstream. expand_stack(vma) fails if address < stack_guard_gap even if there is no vma->vm_prev. I don't think this makes sense, and we didn't do this before the recent commit 1be7107fbe18 ("mm: larger stack guard gap, between vmas"). We do not need a gap in this case, any address is fine as long as security_mmap_addr() doesn't object. This also simplifies the code, we know that address >= prev->vm_end and thus underflow is not possible. Link: http://lkml.kernel.org/r/20170628175258.GA24881@redhat.com Signed-off-by: Oleg Nesterov Acked-by: Michal Hocko Cc: Hugh Dickins Cc: Larry Woodman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Ben Hutchings --- mm/mmap.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2244,7 +2244,6 @@ int expand_downwards(struct vm_area_stru unsigned long address) { struct vm_area_struct *prev; - unsigned long gap_addr; int error; address &= PAGE_MASK; @@ -2253,15 +2252,12 @@ int expand_downwards(struct vm_area_stru return error; /* Enforce stack_guard_gap */ - gap_addr = address - stack_guard_gap; - if (gap_addr > address) - return -ENOMEM; prev = vma->vm_prev; - if (prev && prev->vm_end > gap_addr && + /* Check that both stack segments have the same anon_vma? */ + if (prev && !(prev->vm_flags & VM_GROWSDOWN) && (prev->vm_flags & (VM_WRITE|VM_READ|VM_EXEC))) { - if (!(prev->vm_flags & VM_GROWSDOWN)) + if (address - prev->vm_end < stack_guard_gap) return -ENOMEM; - /* Check that both stack segments have the same anon_vma? */ } /* We must make sure the anon_vma is allocated. */