From patchwork Fri Jun 5 15:15:06 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paolo Bonzini X-Patchwork-Id: 11589869 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id E3B7A618 for ; Fri, 5 Jun 2020 15:15:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C844A206A2 for ; Fri, 5 Jun 2020 15:15:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="NCNF/gBa" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728005AbgFEPP1 (ORCPT ); Fri, 5 Jun 2020 11:15:27 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:37478 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726675AbgFEPP1 (ORCPT ); Fri, 5 Jun 2020 11:15:27 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1591370125; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=fn51+xgx98oZsB/D59Na1SLBQWdWeTshRNoFGM9XJVg=; b=NCNF/gBa0hTVuD4M9eZhbBAnsqZjNTW39qpArPoC25sQPn3H9ly87Y39rT9rqqCWaeSEwH 5iZ/ZoVfIqtYBeYy/PhNpCyVTDbvg6NCnMqP5O7nY/FsRi4W2wCibggfaFnuvsaUcpzeaL fHYyuOCy0e221FT6qGjiaKDP9tPtFXo= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-292-xdjEkaHJNYuWM2jaGqNynA-1; Fri, 05 Jun 2020 11:15:22 -0400 X-MC-Unique: xdjEkaHJNYuWM2jaGqNynA-1 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 mimecast-mx01.redhat.com (Postfix) with ESMTPS id 65E658C7C82; Fri, 5 Jun 2020 15:15:07 +0000 (UTC) Received: from virtlab701.virt.lab.eng.bos.redhat.com (virtlab701.virt.lab.eng.bos.redhat.com [10.19.152.228]) by smtp.corp.redhat.com (Postfix) with ESMTP id CF1DA9CA0; Fri, 5 Jun 2020 15:15:06 +0000 (UTC) From: Paolo Bonzini To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: vkuznets@redhat.com, syzbot+705f4401d5a93a59b87d@syzkaller.appspotmail.com Subject: [PATCH] KVM: let kvm_destroy_vm_debugfs clean up vCPU debugfs directories Date: Fri, 5 Jun 2020 11:15:06 -0400 Message-Id: <20200605151506.18064-1-pbonzini@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org After commit 63d0434 ("KVM: x86: move kvm_create_vcpu_debugfs after last failure point") we are creating the pre-vCPU debugfs files after the creation of the vCPU file descriptor. This makes it possible for userspace to reach kvm_vcpu_release before kvm_create_vcpu_debugfs has finished. The vcpu->debugfs_dentry then does not have any associated inode anymore, and this causes a NULL-pointer dereference in debugfs_create_file. The solution is simply to avoid removing the files; they are cleaned up when the VM file descriptor is closed (and that must be after KVM_CREATE_VCPU returns). We can stop storing the dentry in struct kvm_vcpu too, because it is not needed anywhere after kvm_create_vcpu_debugfs returns. Reported-by: syzbot+705f4401d5a93a59b87d@syzkaller.appspotmail.com Fixes: 63d04348371b ("KVM: x86: move kvm_create_vcpu_debugfs after last failure point") Signed-off-by: Paolo Bonzini --- arch/arm64/kvm/arm.c | 5 ----- arch/x86/kvm/debugfs.c | 10 +++++----- include/linux/kvm_host.h | 3 +-- virt/kvm/kvm_main.c | 8 ++++---- 4 files changed, 10 insertions(+), 16 deletions(-) diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 7a57381c05e8..45276ed50dd6 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -144,11 +144,6 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) return ret; } -int kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu) -{ - return 0; -} - vm_fault_t kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf) { return VM_FAULT_SIGBUS; diff --git a/arch/x86/kvm/debugfs.c b/arch/x86/kvm/debugfs.c index 018aebce33ff..7e818d64bb4d 100644 --- a/arch/x86/kvm/debugfs.c +++ b/arch/x86/kvm/debugfs.c @@ -43,22 +43,22 @@ static int vcpu_get_tsc_scaling_frac_bits(void *data, u64 *val) DEFINE_SIMPLE_ATTRIBUTE(vcpu_tsc_scaling_frac_fops, vcpu_get_tsc_scaling_frac_bits, NULL, "%llu\n"); -void kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu) +void kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu, struct dentry *debugfs_dentry) { - debugfs_create_file("tsc-offset", 0444, vcpu->debugfs_dentry, vcpu, + debugfs_create_file("tsc-offset", 0444, debugfs_dentry, vcpu, &vcpu_tsc_offset_fops); if (lapic_in_kernel(vcpu)) debugfs_create_file("lapic_timer_advance_ns", 0444, - vcpu->debugfs_dentry, vcpu, + debugfs_dentry, vcpu, &vcpu_timer_advance_ns_fops); if (kvm_has_tsc_control) { debugfs_create_file("tsc-scaling-ratio", 0444, - vcpu->debugfs_dentry, vcpu, + debugfs_dentry, vcpu, &vcpu_tsc_scaling_fops); debugfs_create_file("tsc-scaling-ratio-frac-bits", 0444, - vcpu->debugfs_dentry, vcpu, + debugfs_dentry, vcpu, &vcpu_tsc_scaling_frac_fops); } } diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index f43b59b1294c..d38d6b9c24be 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -318,7 +318,6 @@ struct kvm_vcpu { bool preempted; bool ready; struct kvm_vcpu_arch arch; - struct dentry *debugfs_dentry; }; static inline int kvm_vcpu_exiting_guest_mode(struct kvm_vcpu *vcpu) @@ -888,7 +887,7 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu); void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu); #ifdef __KVM_HAVE_ARCH_VCPU_DEBUGFS -void kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu); +void kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu, struct dentry *debugfs_dentry); #endif int kvm_arch_hardware_enable(void); diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 7fa1e38e1659..3577eb84eac0 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2973,7 +2973,6 @@ static int kvm_vcpu_release(struct inode *inode, struct file *filp) { struct kvm_vcpu *vcpu = filp->private_data; - debugfs_remove_recursive(vcpu->debugfs_dentry); kvm_put_kvm(vcpu->kvm); return 0; } @@ -3000,16 +2999,17 @@ static int create_vcpu_fd(struct kvm_vcpu *vcpu) static void kvm_create_vcpu_debugfs(struct kvm_vcpu *vcpu) { #ifdef __KVM_HAVE_ARCH_VCPU_DEBUGFS + struct dentry *debugfs_dentry; char dir_name[ITOA_MAX_LEN * 2]; if (!debugfs_initialized()) return; snprintf(dir_name, sizeof(dir_name), "vcpu%d", vcpu->vcpu_id); - vcpu->debugfs_dentry = debugfs_create_dir(dir_name, - vcpu->kvm->debugfs_dentry); + debugfs_dentry = debugfs_create_dir(dir_name, + vcpu->kvm->debugfs_dentry); - kvm_arch_create_vcpu_debugfs(vcpu); + kvm_arch_create_vcpu_debugfs(vcpu, debugfs_dentry); #endif }