From patchwork Mon Mar 15 18:26:40 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ben Gardon X-Patchwork-Id: 12140401 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=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL 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 717F2C433E6 for ; Mon, 15 Mar 2021 18:27:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 43DDD64F26 for ; Mon, 15 Mar 2021 18:27:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232013AbhCOS1G (ORCPT ); Mon, 15 Mar 2021 14:27:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46762 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232062AbhCOS0z (ORCPT ); Mon, 15 Mar 2021 14:26:55 -0400 Received: from mail-qk1-x74a.google.com (mail-qk1-x74a.google.com [IPv6:2607:f8b0:4864:20::74a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EA738C06174A for ; Mon, 15 Mar 2021 11:26:54 -0700 (PDT) Received: by mail-qk1-x74a.google.com with SMTP id v136so25131360qkb.9 for ; Mon, 15 Mar 2021 11:26:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=kl2EVOBmn7oQV8DsVZaFdaHri6MWqYz7gtsahKZb1Es=; b=Rv6NWFBPwKRKkg6EwJMIts8fimw72c/OGbtenC6IXqCfA3n83O8Dkd5ROm6ba/dSPE SnZXXtvDLj0FCJzCP1AgccjPahos19OWax8j+79Erkty7snq8AbSnIlgukX6CQto5i1+ EJIBv03ENC4fvoUMfBBR+bJTrOdakjsyxpp/E8bqr3RMeN9AjDZh/ERObS6wI8GpK6JZ eRMaWMyO2eBSnGh5pcQxmbbgvkB9DTs2g7BndSD3Se6Q56x3Hovz4VXDw9q2YdGr6cfb 6UAMlHtgyWtYknHs4MaQ0gvnRy0CPwmd8jKGa0px/OwowLIYOEz+B2oguy6vWGdIzwB/ LecA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=kl2EVOBmn7oQV8DsVZaFdaHri6MWqYz7gtsahKZb1Es=; b=uN8Y5if8lWmDTAJlR2UlsqWgBUzoPSCokGZTQLUlFd5dnUj9x3yZltZqOQAa4FTALI HYXLkDgXJHGDobgZ9X9MW1RkhSRuozKsBhvc9r3uXmXLczKyOdU0OxUA0Ty+EPKQrL6T mC/rdaMoffn0bpoP9wPKyTq381bK5hiqF7+LqH2Qob0nCx04ptgs/JhYbTEkjuHVJ/cQ 3v6DRE2E/SXPA6M45R49lGMdzkfZrUsUFo+ugsO3SRyoh1pIaIoZ9pGCzA9YO6sYYNKh dcvOakKzJG6YIyzsTNhbRDpqLQKeXuSQV1zkfpWTAcSgTURoxp+LSuHg4KZpDO0PWw3u 2k7w== X-Gm-Message-State: AOAM531e4ymVgoQ0kikgoQx/PHoTR5ucJHxWvlI3u7lJMJhcrwVP0T0N BkhzlGLwr0lxsYcZnyjZVCbjacEkdQ2n X-Google-Smtp-Source: ABdhPJyz4NSvQIXVCAJ7bB7UPsQH3hv1JaZPjv7eMUgMv/o/R6Al3q67ItDwhcs0ZfqoPuTTjMqaimXw8NZ2 X-Received: from bgardon.sea.corp.google.com ([2620:15c:100:202:888a:4e22:67:844a]) (user=bgardon job=sendgmr) by 2002:a05:6214:aa6:: with SMTP id ew6mr12058104qvb.2.1615832814124; Mon, 15 Mar 2021 11:26:54 -0700 (PDT) Date: Mon, 15 Mar 2021 11:26:40 -0700 In-Reply-To: <20210315182643.2437374-1-bgardon@google.com> Message-Id: <20210315182643.2437374-2-bgardon@google.com> Mime-Version: 1.0 References: <20210315182643.2437374-1-bgardon@google.com> X-Mailer: git-send-email 2.31.0.rc2.261.g7f71774620-goog Subject: [PATCH v2 1/4] KVM: x86/mmu: Fix RCU usage in handle_removed_tdp_mmu_page From: Ben Gardon To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Paolo Bonzini , Sean Christopherson , Peter Shier , Jim Mattson , Ben Gardon , kernel test robot Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org The pt passed into handle_removed_tdp_mmu_page does not need RCU protection, as it is not at any risk of being freed by another thread at that point. However, the implicit cast from tdp_sptep_t to u64 * dropped the __rcu annotation without a proper rcu_derefrence. Fix this by passing the pt as a tdp_ptep_t and then rcu_dereferencing it in the function. Suggested-by: Sean Christopherson Reported-by: kernel test robot Signed-off-by: Ben Gardon --- arch/x86/kvm/mmu/tdp_mmu.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index d78915019b08..db2936cca4bf 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -301,11 +301,16 @@ static void tdp_mmu_unlink_page(struct kvm *kvm, struct kvm_mmu_page *sp, * * Given a page table that has been removed from the TDP paging structure, * iterates through the page table to clear SPTEs and free child page tables. + * + * Note that pt is passed in as a tdp_ptep_t, but it does not need RCU + * protection. Since this thread removed it from the paging structure, + * this thread will be responsible for ensuring the page is freed. Hence the + * early rcu_dereferences in the function. */ -static void handle_removed_tdp_mmu_page(struct kvm *kvm, u64 *pt, +static void handle_removed_tdp_mmu_page(struct kvm *kvm, tdp_ptep_t pt, bool shared) { - struct kvm_mmu_page *sp = sptep_to_sp(pt); + struct kvm_mmu_page *sp = sptep_to_sp(rcu_dereference(pt)); int level = sp->role.level; gfn_t base_gfn = sp->gfn; u64 old_child_spte; @@ -318,7 +323,7 @@ static void handle_removed_tdp_mmu_page(struct kvm *kvm, u64 *pt, tdp_mmu_unlink_page(kvm, sp, shared); for (i = 0; i < PT64_ENT_PER_PAGE; i++) { - sptep = pt + i; + sptep = rcu_dereference(pt) + i; gfn = base_gfn + (i * KVM_PAGES_PER_HPAGE(level - 1)); if (shared) {