From 1eddb85f889a5a9fe59ec184e06844716a00aded Mon Sep 17 00:00:00 2001 From: Christian Borntraeger Date: Thu, 17 Nov 2011 11:00:43 +0100 Subject: [PATCH] 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: Christian Borntraeger Signed-off-by: Carsten Otte Signed-off-by: Avi Kivity --- arch/s390/kvm/priv.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c index 391626361084..d02638959922 100644 --- a/arch/s390/kvm/priv.c +++ b/arch/s390/kvm/priv.c @@ -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(¤t->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(¤t->mm->mmap_sem); return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING); -- 2.30.2