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author | Christian Borntraeger <borntraeger@de.ibm.com> | 2017-12-22 10:54:20 +0100 |
---|---|---|
committer | Christian Borntraeger <borntraeger@de.ibm.com> | 2018-01-24 15:22:51 +0100 |
commit | 1de1ea7efeb9e8543212210e34518b4049ccd285 (patch) | |
tree | 0057ad8dc61f521d48a02caa2708e2e7a76cb6a7 /arch/s390/kvm/kvm-s390.c | |
parent | KVM: s390: prevent buffer overrun on memory hotplug during migration (diff) | |
download | linux-1de1ea7efeb9e8543212210e34518b4049ccd285.tar.xz linux-1de1ea7efeb9e8543212210e34518b4049ccd285.zip |
KVM: s390: add proper locking for CMMA migration bitmap
Some parts of the cmma migration bitmap is already protected
with the kvm->lock (e.g. the migration start). On the other
hand the read of the cmma bits is not protected against a
concurrent free, neither is the emulation of the ESSA instruction.
Let's extend the locking to all related ioctls by using
the slots lock for
- kvm_s390_vm_start_migration
- kvm_s390_vm_stop_migration
- kvm_s390_set_cmma_bits
- kvm_s390_get_cmma_bits
In addition to that, we use synchronize_srcu before freeing
the migration structure as all users hold kvm->srcu for read.
(e.g. the ESSA handler).
Reported-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: stable@vger.kernel.org # 4.13+
Fixes: 190df4a212a7 (KVM: s390: CMMA tracking, ESSA emulation, migration mode)
Reviewed-by: Claudio Imbrenda <imbrenda@linux.vnet.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Diffstat (limited to '')
-rw-r--r-- | arch/s390/kvm/kvm-s390.c | 18 |
1 files changed, 11 insertions, 7 deletions
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index abcd24fdde3f..52880e980a33 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -766,7 +766,7 @@ 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) { @@ -822,7 +822,7 @@ 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) @@ -837,6 +837,8 @@ 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); @@ -846,14 +848,12 @@ 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); @@ -861,7 +861,7 @@ static int kvm_s390_vm_set_migration(struct kvm *kvm, default: break; } - mutex_unlock(&kvm->lock); + mutex_unlock(&kvm->slots_lock); return res; } @@ -1751,7 +1751,9 @@ 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) @@ -1765,7 +1767,9 @@ 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: |