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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 7C983C7618B for ; Wed, 24 Jul 2019 11:37:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3DA5B22387 for ; Wed, 24 Jul 2019 11:37:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727575AbfGXLhP (ORCPT ); Wed, 24 Jul 2019 07:37:15 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59446 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726514AbfGXLhO (ORCPT ); Wed, 24 Jul 2019 07:37:14 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 748FC30BD1B1; Wed, 24 Jul 2019 11:37:14 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.136]) by smtp.corp.redhat.com (Postfix) with SMTP id 53FB760BCE; Wed, 24 Jul 2019 11:37:12 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Wed, 24 Jul 2019 13:37:14 +0200 (CEST) Date: Wed, 24 Jul 2019 13:37:11 +0200 From: Oleg Nesterov To: Song Liu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, matthew.wilcox@oracle.com, kirill.shutemov@linux.intel.com, peterz@infradead.org, rostedt@goodmis.org, kernel-team@fb.com, william.kucharski@oracle.com Subject: Re: [PATCH v8 2/4] uprobe: use original page when all uprobes are removed Message-ID: <20190724113711.GE21599@redhat.com> References: <20190724083600.832091-1-songliubraving@fb.com> <20190724083600.832091-3-songliubraving@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190724083600.832091-3-songliubraving@fb.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Wed, 24 Jul 2019 11:37:14 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/24, Song Liu wrote: > > lock_page(old_page); > @@ -177,15 +180,24 @@ static int __replace_page(struct vm_area_struct *vma, unsigned long addr, > mmu_notifier_invalidate_range_start(&range); > err = -EAGAIN; > if (!page_vma_mapped_walk(&pvmw)) { > - mem_cgroup_cancel_charge(new_page, memcg, false); > + if (!orig) > + mem_cgroup_cancel_charge(new_page, memcg, false); > goto unlock; > } > VM_BUG_ON_PAGE(addr != pvmw.address, old_page); > > get_page(new_page); > - page_add_new_anon_rmap(new_page, vma, addr, false); > - mem_cgroup_commit_charge(new_page, memcg, false, false); > - lru_cache_add_active_or_unevictable(new_page, vma); > + if (orig) { > + lock_page(new_page); /* for page_add_file_rmap() */ > + page_add_file_rmap(new_page, false); Shouldn't we re-check new_page->mapping after lock_page() ? Or we can't race with truncate? and I am worried this code can try to lock the same page twice... Say, the probed application does MADV_DONTNEED and then writes "int3" into vma->vm_file at the same address to fool verify_opcode(). Oleg.