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=-3.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_GIT 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 AC942C28CF6 for ; Wed, 1 Aug 2018 17:36:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4BD5B20862 for ; Wed, 1 Aug 2018 17:36:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4BD5B20862 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2407924AbeHATXI (ORCPT ); Wed, 1 Aug 2018 15:23:08 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:52928 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2436565AbeHATSi (ORCPT ); Wed, 1 Aug 2018 15:18:38 -0400 Received: from localhost (D57E6652.static.ziggozakelijk.nl [213.126.102.82]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id F2B89E24; Wed, 1 Aug 2018 16:53:30 +0000 (UTC) From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tetsuo Handa , Alexander Viro , Rik van Riel , Michal Hocko , "Kirill A. Shutemov" , David Rientjes , Andrew Morton , Linus Torvalds , Sasha Levin Subject: [PATCH 4.17 017/336] mm: check for SIGKILL inside dup_mmap() loop Date: Wed, 1 Aug 2018 18:45:52 +0200 Message-Id: <20180801165029.641924158@linuxfoundation.org> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20180801165028.930831994@linuxfoundation.org> References: <20180801165028.930831994@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.17-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tetsuo Handa [ Upstream commit 655c79bb40a0870adcd0871057d01de11625882b ] As a theoretical problem, dup_mmap() of an mm_struct with 60000+ vmas can loop while potentially allocating memory, with mm->mmap_sem held for write by current thread. This is bad if current thread was selected as an OOM victim, for current thread will continue allocations using memory reserves while OOM reaper is unable to reclaim memory. As an actually observable problem, it is not difficult to make OOM reaper unable to reclaim memory if the OOM victim is blocked at i_mmap_lock_write() in this loop. Unfortunately, since nobody can explain whether it is safe to use killable wait there, let's check for SIGKILL before trying to allocate memory. Even without an OOM event, there is no point with continuing the loop from the beginning if current thread is killed. I tested with debug printk(). This patch should be safe because we already fail if security_vm_enough_memory_mm() or kmem_cache_alloc(GFP_KERNEL) fails and exit_mmap() handles it. ***** Aborting dup_mmap() due to SIGKILL ***** ***** Aborting dup_mmap() due to SIGKILL ***** ***** Aborting dup_mmap() due to SIGKILL ***** ***** Aborting dup_mmap() due to SIGKILL ***** ***** Aborting exit_mmap() due to NULL mmap ***** [akpm@linux-foundation.org: add comment] Link: http://lkml.kernel.org/r/201804071938.CDE04681.SOFVQJFtMHOOLF@I-love.SAKURA.ne.jp Signed-off-by: Tetsuo Handa Cc: Alexander Viro Cc: Rik van Riel Cc: Michal Hocko Cc: Kirill A. Shutemov Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- kernel/fork.c | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/kernel/fork.c +++ b/kernel/fork.c @@ -440,6 +440,14 @@ static __latent_entropy int dup_mmap(str continue; } charge = 0; + /* + * Don't duplicate many vmas if we've been oom-killed (for + * example) + */ + if (fatal_signal_pending(current)) { + retval = -EINTR; + goto out; + } if (mpnt->vm_flags & VM_ACCOUNT) { unsigned long len = vma_pages(mpnt);