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Commit 6d4e4c4f authored by Avi Kivity's avatar Avi Kivity
Browse files

KVM: Disallow fork() and similar games when using a VM 



We don't want the meaning of guest userspace changing under our feet.

Signed-off-by: default avatarAvi Kivity <avi@qumranet.com>
parent 76c35c6e

drivers/kvm/kvm.h

+1 −0
Original line number Diff line number Diff line
@@ -305,6 +305,7 @@ struct kvm_vm_stat { 


struct kvm {

	struct mutex lock; /* protects everything except vcpus */

	struct mm_struct *mm; /* userspace tied to this vm */

	int naliases;

	struct kvm_mem_alias aliases[KVM_ALIAS_SLOTS];

	int nmemslots;

drivers/kvm/kvm_main.c

+9 −0
Original line number Diff line number Diff line
@@ -165,6 +165,8 @@ static struct kvm *kvm_create_vm(void) 
	if (IS_ERR(kvm))

		goto out;



	kvm->mm = current->mm;

	atomic_inc(&kvm->mm->mm_count);

	kvm_io_bus_init(&kvm->pio_bus);

	mutex_init(&kvm->lock);

	kvm_io_bus_init(&kvm->mmio_bus);
@@ -202,12 +204,15 @@ void kvm_free_physmem(struct kvm *kvm) 


static void kvm_destroy_vm(struct kvm *kvm)

{

	struct mm_struct *mm = kvm->mm;



	spin_lock(&kvm_lock);

	list_del(&kvm->vm_list);

	spin_unlock(&kvm_lock);

	kvm_io_bus_destroy(&kvm->pio_bus);

	kvm_io_bus_destroy(&kvm->mmio_bus);

	kvm_arch_destroy_vm(kvm);

	mmdrop(mm);

}



static int kvm_vm_release(struct inode *inode, struct file *filp)
@@ -818,6 +823,8 @@ static long kvm_vcpu_ioctl(struct file *filp, 
	void __user *argp = (void __user *)arg;

	int r;



	if (vcpu->kvm->mm != current->mm)

		return -EIO;

	switch (ioctl) {

	case KVM_RUN:

		r = -EINVAL;
@@ -976,6 +983,8 @@ static long kvm_vm_ioctl(struct file *filp, 
	void __user *argp = (void __user *)arg;

	int r;



	if (kvm->mm != current->mm)

		return -EIO;

	switch (ioctl) {

	case KVM_CREATE_VCPU:

		r = kvm_vm_ioctl_create_vcpu(kvm, arg);

kernel/fork.c

+1 −0
Original line number Diff line number Diff line
@@ -393,6 +393,7 @@ void fastcall __mmdrop(struct mm_struct *mm) 
	destroy_context(mm);

	free_mm(mm);

}

EXPORT_SYMBOL_GPL(__mmdrop);



/*

 * Decrement the use count and release all resources for an mm.