From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4BE7B4431 for ; Wed, 15 Mar 2023 12:25:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C5EC8C433D2; Wed, 15 Mar 2023 12:25:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1678883106; bh=sLMcxmgFcy0JI0mH6rhzsoWCnvbGt44f7d5JvNr5fZ0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kA2+tMtuonOjKqZQh+AY7noFOPIwUAUbBF18BhEF4VT6wwgyM8O9W7MmveDjd5PNZ xKQmMBwcUwRQz0c1djxCzbmOe8ZzYF6JxXNOb6Ff0e+dFVeY5OQgN8XJlxFl2dE8qS L9rp0CLsorz/cuKHe2XhQqyhzBpeL1MimRToDtjE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Sean Christopherson , Paolo Bonzini , Sasha Levin Subject: [PATCH 5.15 018/145] KVM: Register /dev/kvm as the _very_ last thing during initialization Date: Wed, 15 Mar 2023 13:11:24 +0100 Message-Id: <20230315115739.607263555@linuxfoundation.org> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230315115738.951067403@linuxfoundation.org> References: <20230315115738.951067403@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Sean Christopherson [ Upstream commit 2b01281273738bf2d6551da48d65db2df3f28998 ] Register /dev/kvm, i.e. expose KVM to userspace, only after all other setup has completed. Once /dev/kvm is exposed, userspace can start invoking KVM ioctls, creating VMs, etc... If userspace creates a VM before KVM is done with its configuration, bad things may happen, e.g. KVM will fail to properly migrate vCPU state if a VM is created before KVM has registered preemption notifiers. Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson Message-Id: <20221130230934.1014142-2-seanjc@google.com> Signed-off-by: Paolo Bonzini Signed-off-by: Sasha Levin --- virt/kvm/kvm_main.c | 31 ++++++++++++++++++++++--------- 1 file changed, 22 insertions(+), 9 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index c60e88b0b24ec..17e22c654c4e4 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -5655,12 +5655,6 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align, kvm_vm_fops.owner = module; kvm_vcpu_fops.owner = module; - r = misc_register(&kvm_dev); - if (r) { - pr_err("kvm: misc device register failed\n"); - goto out_unreg; - } - register_syscore_ops(&kvm_syscore_ops); kvm_preempt_ops.sched_in = kvm_sched_in; @@ -5669,11 +5663,24 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align, kvm_init_debug(); r = kvm_vfio_ops_init(); - WARN_ON(r); + if (WARN_ON_ONCE(r)) + goto err_vfio; + + /* + * Registration _must_ be the very last thing done, as this exposes + * /dev/kvm to userspace, i.e. all infrastructure must be setup! + */ + r = misc_register(&kvm_dev); + if (r) { + pr_err("kvm: misc device register failed\n"); + goto err_register; + } return 0; -out_unreg: +err_register: + kvm_vfio_ops_exit(); +err_vfio: kvm_async_pf_deinit(); out_free_5: for_each_possible_cpu(cpu) @@ -5700,8 +5707,14 @@ void kvm_exit(void) { int cpu; - debugfs_remove_recursive(kvm_debugfs_dir); + /* + * Note, unregistering /dev/kvm doesn't strictly need to come first, + * fops_get(), a.k.a. try_module_get(), prevents acquiring references + * to KVM while the module is being stopped. + */ misc_deregister(&kvm_dev); + + debugfs_remove_recursive(kvm_debugfs_dir); for_each_possible_cpu(cpu) free_cpumask_var(per_cpu(cpu_kick_mask, cpu)); kmem_cache_destroy(kvm_vcpu_cache); -- 2.39.2