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authorChristian Borntraeger <borntraeger@de.ibm.com>2011-11-17 11:00:43 +0100
committerAvi Kivity <avi@redhat.com>2011-11-17 16:25:48 +0200
commit1eddb85f889a5a9fe59ec184e06844716a00aded (patch)
treec789c7cd507f3e5fa5150dc8f6e44efc1e2ab866
parentbd59d3a4444e5f941c863db1a7715edf7289e29a (diff)
downloadlinux-1eddb85f889a5a9fe59ec184e06844716a00aded.tar.bz2
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 <borntraeger@de.ibm.com> Signed-off-by: Carsten Otte <cotte@de.ibm.com> Signed-off-by: Avi Kivity <avi@redhat.com>
-rw-r--r--arch/s390/kvm/priv.c10
1 files 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(&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);