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Commit 1eddb85f authored by Christian Borntraeger's avatar Christian Borntraeger Committed by Avi Kivity
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KVM: s390: Fix tprot locking 



There is a potential host deadlock in the tprot intercept handling.
We must not hold the mmap semaphore while resolving the guest
address. If userspace is remapping, then the memory detection in
the guest is broken anyway so we can safely separate the
address translation from walking the vmas.

Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarCarsten Otte <cotte@de.ibm.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent bd59d3a4

arch/s390/kvm/priv.c

+8 −2
Original line number Diff line number Diff line
@@ -336,6 +336,7 @@ static int handle_tprot(struct kvm_vcpu *vcpu) 
	u64 address1 = disp1 + base1 ? vcpu->arch.guest_gprs[base1] : 0;

	u64 address2 = disp2 + base2 ? vcpu->arch.guest_gprs[base2] : 0;

	struct vm_area_struct *vma;

	unsigned long user_address;



	vcpu->stat.instruction_tprot++;
@@ -349,9 +350,14 @@ static int handle_tprot(struct kvm_vcpu *vcpu) 
		return -EOPNOTSUPP;





	/* we must resolve the address without holding the mmap semaphore.

	 * This is ok since the userspace hypervisor is not supposed to change

	 * the mapping while the guest queries the memory. Otherwise the guest

	 * might crash or get wrong info anyway. */

	user_address = (unsigned long) __guestaddr_to_user(vcpu, address1);



	down_read(&current->mm->mmap_sem);

	vma = find_vma(current->mm,

			(unsigned long) __guestaddr_to_user(vcpu, address1));

	vma = find_vma(current->mm, user_address);

	if (!vma) {

		up_read(&current->mm->mmap_sem);

		return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);