[libvirt] [PATCH v2] qemu: migration: Don't crash on access to 'current' job

[Peter Krempa]

When a VM is destroyed while being migrated (waiting in
qemuMigrationSrcWaitForCompletion) the private object cleanup code frees
the 'current' job info. Since the migration code attempts to setup
various aspects of the current job even on failure this results into a
crash.

Job data is cleared in qemuDomainObjPrivateDataClear since commit
888aa4b6b9db

Fix this by skipping all of the code which requires the qemu process to
be alive if the VM is not active any more.

Signed-off-by: Peter Krempa <pkrempa at redhat.com>
---
 src/qemu/qemu_migration.c | 33 +++++++++++++++++----------------
 1 file changed, 17 insertions(+), 16 deletions(-)

diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
index b913e99928..1a857329ec 100644
--- a/src/qemu/qemu_migration.c
+++ b/src/qemu/qemu_migration.c
@@ -3561,27 +3561,28 @@ qemuMigrationSrcRun(virQEMUDriverPtr driver,
  error:
     orig_err = virSaveLastError();

-    if (cancel &&
-        priv->job.current->status != QEMU_DOMAIN_JOB_STATUS_QEMU_COMPLETED &&
-        virDomainObjIsActive(vm) &&
-        qemuDomainObjEnterMonitorAsync(driver, vm,
-                                       QEMU_ASYNC_JOB_MIGRATION_OUT) == 0) {
-        qemuMonitorMigrateCancel(priv->mon);
-        ignore_value(qemuDomainObjExitMonitor(driver, vm));
-    }
+    if (virDomainObjIsActive(vm)) {
+        if (cancel &&
+            priv->job.current->status != QEMU_DOMAIN_JOB_STATUS_QEMU_COMPLETED &&
+            qemuDomainObjEnterMonitorAsync(driver, vm,
+                                           QEMU_ASYNC_JOB_MIGRATION_OUT) == 0) {
+            qemuMonitorMigrateCancel(priv->mon);
+            ignore_value(qemuDomainObjExitMonitor(driver, vm));
+        }

-    /* cancel any outstanding NBD jobs */
-    if (mig && mig->nbd)
-        qemuMigrationSrcCancelDriveMirror(driver, vm, false,
-                                          QEMU_ASYNC_JOB_MIGRATION_OUT,
-                                          dconn);
+        /* cancel any outstanding NBD jobs */
+        if (mig && mig->nbd)
+            qemuMigrationSrcCancelDriveMirror(driver, vm, false,
+                                              QEMU_ASYNC_JOB_MIGRATION_OUT,
+                                              dconn);
+
+        if (priv->job.current->status != QEMU_DOMAIN_JOB_STATUS_CANCELED)
+            priv->job.current->status = QEMU_DOMAIN_JOB_STATUS_FAILED;
+    }

     if (iothread)
         qemuMigrationSrcStopTunnel(iothread, true);

-    if (priv->job.current->status != QEMU_DOMAIN_JOB_STATUS_CANCELED)
-        priv->job.current->status = QEMU_DOMAIN_JOB_STATUS_FAILED;
-
     goto cleanup;

  exit_monitor:
-- 
2.16.2