From patchwork Thu Mar 3 18:33:27 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Matlack X-Patchwork-Id: 12767932 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1E9F6C433EF for ; Thu, 3 Mar 2022 18:33:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234716AbiCCSeV (ORCPT ); Thu, 3 Mar 2022 13:34:21 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43884 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233849AbiCCSeT (ORCPT ); Thu, 3 Mar 2022 13:34:19 -0500 Received: from mail-pj1-x1049.google.com (mail-pj1-x1049.google.com [IPv6:2607:f8b0:4864:20::1049]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6879E10A7C4 for ; Thu, 3 Mar 2022 10:33:33 -0800 (PST) Received: by mail-pj1-x1049.google.com with SMTP id o41-20020a17090a0a2c00b001bf06e5badfso1986489pjo.3 for ; Thu, 03 Mar 2022 10:33:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=QOuZ5I4KFRMXkF6seWShnE2Ey6ez7qDQdhK2bClCPu0=; b=lDeisK5cHZpbtWacdaMm9AZjhDaWYo10ffNAXW4GS7AdNAyg+Hh/n56SMXrjaBrBGB UvG1CT+h6m7qNJsCzbDviTmDG+Bovty9yvh5u/fbAP5+WCF779/YNu4zcmVpMKMUJVCo kZDdVS4rlis+mXQWEAkHZU9clHM/euY6G6PR/1YG6sVnB8FymzRzfSiKZC8/Qqd+irdT oJpjpOTjYdxq7uGIZj8weZuQIPQh4OBN3TN+afP/g1QU5r2EzbcIlPCFVLoI2xuUAkvE FFOGmwmAtvioZej3cVRpljxne8EKoY4dt3ef0lJEaIyrJiHLZIyNShsen+31akNCCDZl c8fA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=QOuZ5I4KFRMXkF6seWShnE2Ey6ez7qDQdhK2bClCPu0=; b=RDuZhHZwuFv3u8wnoDfkSaCJlWGYbNZ8jKV1cXcqhupSZzAFKE2mLF43ItQ2isuA0b UI39oY0kni90byzNnvhFJ+O2c6vzBNDWd0O2dDnzxn7fnmRejbXRv3gQa3GRCyMEW4k6 yC7NNaJ0dg8FYTnhSKVoGnpVNoFTNFoapY+43czLMbKQsk3dUklUlqdufNyg2DP/4LZZ EC52iwxNmWBKX7UkhHLrmFmkKACcereyDg9fQmNNyImpjgfCnhyGwpdSt7svshHmv9m0 uREEcXY3k3xIT3uZMstyrwOjK1J5cwhC9qfV/HYvvSGJTb1Uk9sAEu++zuQ5cDgtLlll DCBg== X-Gm-Message-State: AOAM533AG1hm6r+Gj+y44lFgGJprsT/40PCMOjxd2UXxui5AVo4Clhpg rHUCe40yew/Rkh36DAMokpEt6AnXsFJgHQ== X-Google-Smtp-Source: ABdhPJyMOASFXqZeTTIqtYO0itzLRZL9uApqq7mmkmPJO9JZ5PbxYzX10D2vZj7kQXTCDJOFzri0PvVd+gYYTQ== X-Received: from dmatlack-heavy.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:19cd]) (user=dmatlack job=sendgmr) by 2002:a17:902:b602:b0:14f:e42b:d547 with SMTP id b2-20020a170902b60200b0014fe42bd547mr37940828pls.91.1646332412852; Thu, 03 Mar 2022 10:33:32 -0800 (PST) Date: Thu, 3 Mar 2022 18:33:27 +0000 In-Reply-To: <20220303183328.1499189-1-dmatlack@google.com> Message-Id: <20220303183328.1499189-2-dmatlack@google.com> Mime-Version: 1.0 References: <20220303183328.1499189-1-dmatlack@google.com> X-Mailer: git-send-email 2.35.1.616.g0bdcbb4464-goog Subject: [PATCH RESEND 1/2] KVM: Prevent module exit until all VMs are freed From: David Matlack To: pbonzini@redhat.com Cc: David Matlack , kvm@vger.kernel.org, Marcelo Tosatti , Gleb Natapov , Rik van Riel , seanjc@google.com, bgardon@google.com, stable@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Tie the lifetime the KVM module to the lifetime of each VM via kvm.users_count. This way anything that grabs a reference to the VM via kvm_get_kvm() cannot accidentally outlive the KVM module. Prior to this commit, the lifetime of the KVM module was tied to the lifetime of /dev/kvm file descriptors, VM file descriptors, and vCPU file descriptors by their respective file_operations "owner" field. This approach is insufficient because references grabbed via kvm_get_kvm() do not prevent closing any of the aforementioned file descriptors. This fixes a long standing theoretical bug in KVM that at least affects async page faults. kvm_setup_async_pf() grabs a reference via kvm_get_kvm(), and drops it in an asynchronous work callback. Nothing prevents the VM file descriptor from being closed and the KVM module from being unloaded before this callback runs. Fixes: af585b921e5d ("KVM: Halt vcpu if page it tries to access is swapped out") Cc: stable@vger.kernel.org Suggested-by: Ben Gardon [ Based on a patch from Ben implemented for Google's kernel. ] Signed-off-by: David Matlack Reviewed-by: Sean Christopherson --- virt/kvm/kvm_main.c | 8 ++++++++ 1 file changed, 8 insertions(+) base-commit: b13a3befc815eae574d87e6249f973dfbb6ad6cd prerequisite-patch-id: 38f66d60319bf0bc9bf49f91f0f9119e5441629b prerequisite-patch-id: 51aa921d68ea649d436ea68e1b8f4aabc3805156 diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 35ae6d32dae5..b59f0a29dbd5 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -117,6 +117,8 @@ EXPORT_SYMBOL_GPL(kvm_debugfs_dir); static const struct file_operations stat_fops_per_vm; +static struct file_operations kvm_chardev_ops; + static long kvm_vcpu_ioctl(struct file *file, unsigned int ioctl, unsigned long arg); #ifdef CONFIG_KVM_COMPAT @@ -1131,6 +1133,11 @@ static struct kvm *kvm_create_vm(unsigned long type) preempt_notifier_inc(); kvm_init_pm_notifier(kvm); + if (!try_module_get(kvm_chardev_ops.owner)) { + r = -ENODEV; + goto out_err; + } + return kvm; out_err: @@ -1220,6 +1227,7 @@ static void kvm_destroy_vm(struct kvm *kvm) preempt_notifier_dec(); hardware_disable_all(); mmdrop(mm); + module_put(kvm_chardev_ops.owner); } void kvm_get_kvm(struct kvm *kvm)