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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E5F09C433EF for ; Mon, 11 Jul 2022 09:52:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233842AbiGKJwE (ORCPT ); Mon, 11 Jul 2022 05:52:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56990 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233843AbiGKJup (ORCPT ); Mon, 11 Jul 2022 05:50:45 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0CCAB29830; Mon, 11 Jul 2022 02:25:02 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 9EE38B80E7A; Mon, 11 Jul 2022 09:25:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0F1DAC34115; Mon, 11 Jul 2022 09:24:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1657531499; bh=jLg70Q9nZHijQ04V8fPVGvO1b75QYGWIzu9gmbZ9Xr0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OGg2gj4XzgitG/GO3LyXj39N1tFw364Ok67w5cnx+p4enDl45qvTIafk41NITHF8f 3ody7LDM1/vXk3XYW86x61aIRRp6ZoqhMvv3lSwSvLaivMOGIV9Wdb06a/MgeauAS1 6tpWhfXs+XcD/b90+UUsvul32ConanwhcRcycNDQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Marc Zyngier , Oliver Upton , syzbot+df6fbbd2ee39f21289ef@syzkaller.appspotmail.com, Sean Christopherson , Paolo Bonzini , Sasha Levin Subject: [PATCH 5.15 126/230] KVM: Initialize debugfs_dentry when a VM is created to avoid NULL deref Date: Mon, 11 Jul 2022 11:06:22 +0200 Message-Id: <20220711090607.639773751@linuxfoundation.org> X-Mailer: git-send-email 2.37.0 In-Reply-To: <20220711090604.055883544@linuxfoundation.org> References: <20220711090604.055883544@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Sean Christopherson [ Upstream commit 5c697c367a66307a5d943c3449421aff2aa3ca4a ] Initialize debugfs_entry to its semi-magical -ENOENT value when the VM is created. KVM's teardown when VM creation fails is kludgy and calls kvm_uevent_notify_change() and kvm_destroy_vm_debugfs() even if KVM never attempted kvm_create_vm_debugfs(). Because debugfs_entry is zero initialized, the IS_ERR() checks pass and KVM derefs a NULL pointer. BUG: kernel NULL pointer dereference, address: 0000000000000018 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 1068b1067 P4D 1068b1067 PUD 1068b0067 PMD 0 Oops: 0000 [#1] SMP CPU: 0 PID: 871 Comm: repro Not tainted 5.18.0-rc1+ #825 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:__dentry_path+0x7b/0x130 Call Trace: dentry_path_raw+0x42/0x70 kvm_uevent_notify_change.part.0+0x10c/0x200 [kvm] kvm_put_kvm+0x63/0x2b0 [kvm] kvm_dev_ioctl+0x43a/0x920 [kvm] __x64_sys_ioctl+0x83/0xb0 do_syscall_64+0x31/0x50 entry_SYSCALL_64_after_hwframe+0x44/0xae Modules linked in: kvm_intel kvm irqbypass Fixes: a44a4cc1c969 ("KVM: Don't create VM debugfs files outside of the VM directory") Cc: stable@vger.kernel.org Cc: Marc Zyngier Cc: Oliver Upton Reported-by: syzbot+df6fbbd2ee39f21289ef@syzkaller.appspotmail.com Signed-off-by: Sean Christopherson Reviewed-by: Oliver Upton Message-Id: <20220415004622.2207751-1-seanjc@google.com> Signed-off-by: Paolo Bonzini Signed-off-by: Sasha Levin --- virt/kvm/kvm_main.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 9134ae252d7c..9eac68ae291e 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -934,12 +934,6 @@ static int kvm_create_vm_debugfs(struct kvm *kvm, int fd) int kvm_debugfs_num_entries = kvm_vm_stats_header.num_desc + kvm_vcpu_stats_header.num_desc; - /* - * Force subsequent debugfs file creations to fail if the VM directory - * is not created. - */ - kvm->debugfs_dentry = ERR_PTR(-ENOENT); - if (!debugfs_initialized()) return 0; @@ -1055,6 +1049,12 @@ static struct kvm *kvm_create_vm(unsigned long type) BUILD_BUG_ON(KVM_MEM_SLOTS_NUM > SHRT_MAX); + /* + * Force subsequent debugfs file creations to fail if the VM directory + * is not created (by kvm_create_vm_debugfs()). + */ + kvm->debugfs_dentry = ERR_PTR(-ENOENT); + if (init_srcu_struct(&kvm->srcu)) goto out_err_no_srcu; if (init_srcu_struct(&kvm->irq_srcu)) -- 2.35.1