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KVM fixes for v4.15(-rc10)

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Fix races and potential use after free in the s390 cmma migration code.
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

Pull KVM fixes from Radim Krčmář:
 "Fix races and a potential use after free in the s390 cmma migration
  code"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
  KVM: s390: add proper locking for CMMA migration bitmap
This commit is contained in:
Linus Torvalds 2018-01-25 09:32:10 -08:00
commit 6e20630e30
1 changed files with 11 additions and 7 deletions
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18
arch/s390/kvm/kvm-s390.c
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@ -769,7 +769,7 @@ static void kvm_s390_sync_request_broadcast(struct kvm *kvm, int req)
/*
* Must be called with kvm->srcu held to avoid races on memslots, and with
* kvm->lock to avoid races with ourselves and kvm_s390_vm_stop_migration.
* kvm->slots_lock to avoid races with ourselves and kvm_s390_vm_stop_migration.
*/
static int kvm_s390_vm_start_migration(struct kvm *kvm)
{
@ -825,7 +825,7 @@ static int kvm_s390_vm_start_migration(struct kvm *kvm)
}
/*
* Must be called with kvm->lock to avoid races with ourselves and
* Must be called with kvm->slots_lock to avoid races with ourselves and
* kvm_s390_vm_start_migration.
*/
static int kvm_s390_vm_stop_migration(struct kvm *kvm)
@ -840,6 +840,8 @@ static int kvm_s390_vm_stop_migration(struct kvm *kvm)
if (kvm->arch.use_cmma) {
kvm_s390_sync_request_broadcast(kvm, KVM_REQ_STOP_MIGRATION);
/* We have to wait for the essa emulation to finish */
synchronize_srcu(&kvm->srcu);
vfree(mgs->pgste_bitmap);
}
kfree(mgs);
@ -849,14 +851,12 @@ static int kvm_s390_vm_stop_migration(struct kvm *kvm)
static int kvm_s390_vm_set_migration(struct kvm *kvm,
struct kvm_device_attr *attr)
{
int idx, res = -ENXIO;
int res = -ENXIO;
mutex_lock(&kvm->lock);
mutex_lock(&kvm->slots_lock);
switch (attr->attr) {
case KVM_S390_VM_MIGRATION_START:
idx = srcu_read_lock(&kvm->srcu);
res = kvm_s390_vm_start_migration(kvm);
srcu_read_unlock(&kvm->srcu, idx);
break;
case KVM_S390_VM_MIGRATION_STOP:
res = kvm_s390_vm_stop_migration(kvm);
@ -864,7 +864,7 @@ static int kvm_s390_vm_set_migration(struct kvm *kvm,
default:
break;
}
mutex_unlock(&kvm->lock);
mutex_unlock(&kvm->slots_lock);
return res;
}
@ -1754,7 +1754,9 @@ long kvm_arch_vm_ioctl(struct file *filp,
r = -EFAULT;
if (copy_from_user(&args, argp, sizeof(args)))
break;
mutex_lock(&kvm->slots_lock);
r = kvm_s390_get_cmma_bits(kvm, &args);
mutex_unlock(&kvm->slots_lock);
if (!r) {
r = copy_to_user(argp, &args, sizeof(args));
if (r)
@ -1768,7 +1770,9 @@ long kvm_arch_vm_ioctl(struct file *filp,
r = -EFAULT;
if (copy_from_user(&args, argp, sizeof(args)))
break;
mutex_lock(&kvm->slots_lock);
r = kvm_s390_set_cmma_bits(kvm, &args);
mutex_unlock(&kvm->slots_lock);
break;
}
default: