[PATCH 3/5] qemu: snapshot: Acquire job earlier on snapshot revert/delete

[Peter Krempa <pkrempa@xxxxxxxxxx>]

From: Jincheng Miao <jmiao@xxxxxxxxxx>

The code would lookup the snapshot object before acquiring the job. This
could lead to a crash as one thread could delete the snapshot object,
while a second thread already had the reference.

Signed-off-by: Jincheng Miao <jmiao@xxxxxxxxxx>
Signed-off-by: Peter Krempa <pkrempa@xxxxxxxxxx>
---
 src/qemu/qemu_driver.c | 30 +++++++++++++++---------------
 1 file changed, 15 insertions(+), 15 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 9f200f0..8e5c353 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -14013,9 +14013,12 @@ static int qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
         goto cleanup;
     }

-    if (!(snap = qemuSnapObjFromSnapshot(vm, snapshot)))
+    if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_MODIFY) < 0)
         goto cleanup;

+    if (!(snap = qemuSnapObjFromSnapshot(vm, snapshot)))
+        goto endjob;
+
     if (!vm->persistent &&
         snap->def->state != VIR_DOMAIN_RUNNING &&
         snap->def->state != VIR_DOMAIN_PAUSED &&
@@ -14024,13 +14027,13 @@ static int qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
         virReportError(VIR_ERR_OPERATION_INVALID, "%s",
                        _("transient domain needs to request run or pause "
                          "to revert to inactive snapshot"));
-        goto cleanup;
+        goto endjob;
     }

     if (virDomainSnapshotIsExternal(snap)) {
         virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
                        _("revert to external snapshot not supported yet"));
-        goto cleanup;
+        goto endjob;
     }

     if (!(flags & VIR_DOMAIN_SNAPSHOT_REVERT_FORCE)) {
@@ -14038,7 +14041,7 @@ static int qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
             virReportError(VIR_ERR_SNAPSHOT_REVERT_RISKY,
                            _("snapshot '%s' lacks domain '%s' rollback info"),
                            snap->def->name, vm->def->name);
-            goto cleanup;
+            goto endjob;
         }
         if (virDomainObjIsActive(vm) &&
             !(snap->def->state == VIR_DOMAIN_RUNNING
@@ -14047,7 +14050,7 @@ static int qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
                       VIR_DOMAIN_SNAPSHOT_REVERT_PAUSED))) {
             virReportError(VIR_ERR_SNAPSHOT_REVERT_RISKY, "%s",
                            _("must respawn qemu to start inactive snapshot"));
-            goto cleanup;
+            goto endjob;
         }
     }

@@ -14056,7 +14059,7 @@ static int qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
         vm->current_snapshot->def->current = false;
         if (qemuDomainSnapshotWriteMetadata(vm, vm->current_snapshot,
                                             cfg->snapshotDir) < 0)
-            goto cleanup;
+            goto endjob;
         vm->current_snapshot = NULL;
         /* XXX Should we restore vm->current_snapshot after this point
          * in the failure cases where we know there was no change?  */
@@ -14071,12 +14074,9 @@ static int qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
     if (snap->def->dom) {
         config = virDomainDefCopy(snap->def->dom, caps, driver->xmlopt, true);
         if (!config)
-            goto cleanup;
+            goto endjob;
     }

-    if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_MODIFY) < 0)
-        goto cleanup;
-
     switch ((virDomainState) snap->def->state) {
     case VIR_DOMAIN_RUNNING:
     case VIR_DOMAIN_PAUSED:
@@ -14386,9 +14386,12 @@ static int qemuDomainSnapshotDelete(virDomainSnapshotPtr snapshot,
     if (virDomainSnapshotDeleteEnsureACL(snapshot->domain->conn, vm->def) < 0)
         goto cleanup;

-    if (!(snap = qemuSnapObjFromSnapshot(vm, snapshot)))
+    if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_MODIFY) < 0)
         goto cleanup;

+    if (!(snap = qemuSnapObjFromSnapshot(vm, snapshot)))
+        goto endjob;
+
     if (!metadata_only) {
         if (!(flags & VIR_DOMAIN_SNAPSHOT_DELETE_CHILDREN_ONLY) &&
             virDomainSnapshotIsExternal(snap))
@@ -14401,13 +14404,10 @@ static int qemuDomainSnapshotDelete(virDomainSnapshotPtr snapshot,
             virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
                            _("deletion of %d external disk snapshots not "
                              "supported yet"), external);
-            goto cleanup;
+            goto endjob;
         }
     }

-    if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_MODIFY) < 0)
-        goto cleanup;
-
     if (flags & (VIR_DOMAIN_SNAPSHOT_DELETE_CHILDREN |
                  VIR_DOMAIN_SNAPSHOT_DELETE_CHILDREN_ONLY)) {
         rem.driver = driver;
-- 
2.0.2

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