From patchwork Thu Sep 9 21:06:21 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 508739 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=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, 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 CF540C433F5 for ; Thu, 9 Sep 2021 21:07:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B43D761186 for ; Thu, 9 Sep 2021 21:07:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232891AbhIIVIN (ORCPT ); Thu, 9 Sep 2021 17:08:13 -0400 Received: from mail.kernel.org ([198.145.29.99]:57228 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348160AbhIIVHb (ORCPT ); Thu, 9 Sep 2021 17:07:31 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 72B9D611B0; Thu, 9 Sep 2021 21:06:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1631221581; bh=AxJCkDEpShrQUlXh5uda1KrXeb96xr+L4noP5Mh8mKc=; h=Date:From:To:Subject:From; b=xlnj+VUOZQ732MWNAGpHjbfNvJ4iCvxV3drjBFyh54sGXwo7M2CELYKCV6E2GvqXS YDMB1AUneIiqif9XqPyFc77C6pjPo7XbWqNrIrac0wiyM2LNDPguUXA0cuE1fX+fwk sDu5wnx8HbyAFzmrXK6H6oFZRxr/gkHH6RGnXk6o= Date: Thu, 09 Sep 2021 14:06:21 -0700 From: akpm@linux-foundation.org To: mm-commits@vger.kernel.org, songmuchun@bytedance.com, stable@vger.kernel.org, yanghui.def@bytedance.com Subject: [merged] mm-mempolicy-fix-a-race-between-offset_il_node-and-mpol_rebind_task.patch removed from -mm tree Message-ID: <20210909210621.ei9jo8-8M%akpm@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch titled Subject: mm/mempolicy: fix a race between offset_il_node and mpol_rebind_task has been removed from the -mm tree. Its filename was mm-mempolicy-fix-a-race-between-offset_il_node-and-mpol_rebind_task.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: yanghui Subject: mm/mempolicy: fix a race between offset_il_node and mpol_rebind_task Servers happened below panic: Kernel version:5.4.56 BUG: unable to handle page fault for address: 0000000000002c48 RIP: 0010:__next_zones_zonelist+0x1d/0x40 [264003.977696] RAX: 0000000000002c40 RBX: 0000000000100dca RCX: 0000000000000014 [264003.977872] Call Trace: [264003.977888] __alloc_pages_nodemask+0x277/0x310 [264003.977908] alloc_page_interleave+0x13/0x70 [264003.977926] handle_mm_fault+0xf99/0x1390 [264003.977951] __do_page_fault+0x288/0x500 [264003.977979] ? schedule+0x39/0xa0 [264003.977994] do_page_fault+0x30/0x110 [264003.978010] page_fault+0x3e/0x50 The reason for the panic is that MAX_NUMNODES is passed in the third parameter in __alloc_pages_nodemask(preferred_nid). So access to zonelist->zoneref->zone_idx in __next_zones_zonelist will cause a panic. In offset_il_node(), first_node() returns nid from pol->v.nodes, after this other threads may chang pol->v.nodes before next_node(). This race condition will let next_node return MAX_NUMNODES. So put pol->nodes in a local variable. The race condition is between offset_il_node and cpuset_change_task_nodemask: CPU0: CPU1: alloc_pages_vma() interleave_nid(pol,) offset_il_node(pol,) first_node(pol->v.nodes) cpuset_change_task_nodemask //nodes==0xc mpol_rebind_task mpol_rebind_policy mpol_rebind_nodemask(pol,nodes) //nodes==0x3 next_node(nid, pol->v.nodes)//return MAX_NUMNODES Link: https://lkml.kernel.org/r/20210906034658.48721-1-yanghui.def@bytedance.com Signed-off-by: yanghui Reviewed-by: Muchun Song Cc: Signed-off-by: Andrew Morton --- mm/mempolicy.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) --- a/mm/mempolicy.c~mm-mempolicy-fix-a-race-between-offset_il_node-and-mpol_rebind_task +++ a/mm/mempolicy.c @@ -1876,17 +1876,26 @@ unsigned int mempolicy_slab_node(void) */ static unsigned offset_il_node(struct mempolicy *pol, unsigned long n) { - unsigned nnodes = nodes_weight(pol->nodes); - unsigned target; + nodemask_t nodemask = pol->nodes; + unsigned int target, nnodes; int i; int nid; + /* + * The barrier will stabilize the nodemask in a register or on + * the stack so that it will stop changing under the code. + * + * Between first_node() and next_node(), pol->nodes could be changed + * by other threads. So we put pol->nodes in a local stack. + */ + barrier(); + nnodes = nodes_weight(nodemask); if (!nnodes) return numa_node_id(); target = (unsigned int)n % nnodes; - nid = first_node(pol->nodes); + nid = first_node(nodemask); for (i = 0; i < target; i++) - nid = next_node(nid, pol->nodes); + nid = next_node(nid, nodemask); return nid; }