[libvirt] [PATCH v1 10/11] storage_driver: Protect pool def during startup and build

[Michal Privoznik]

In near future the storage pool object lock will be released
during startPool and buildPool callback (in some backends). But
this means that another thread may acquire the pool object lock
and change its definition rendering the former thread access not
only stale definition but also access freed memory
(virStoragePoolObjAssignDef() will free old def when setting a
new one).

One way out of this would be to have the pool appear as active
because our code deals with obj->def and obj->newdef just fine.
But we can't declare a pool as active if it's not started or
still building up. Therefore, have a boolean flag that is very
similar and forces virStoragePoolObjAssignDef() to store new
definition in obj->newdef even for an inactive pool. In turn, we
have to move the definition to correct place when unsetting the
flag. But that's as easy as calling
virStoragePoolUpdateInactive().

Technically speaking, change made to
storageDriverAutostartCallback() is not needed because until
storage driver is initialized no storage API can run therefore
there can't be anyone wanting to change the pool's definition.
But I'm doing the change there for consistency anyways.

Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
---
 src/conf/virstorageobj.c     | 26 +++++++++++++++++++++++++-
 src/conf/virstorageobj.h     |  6 ++++++
 src/libvirt_private.syms     |  2 ++
 src/storage/storage_driver.c | 31 ++++++++++++++++++++++++++++++-
 4 files changed, 63 insertions(+), 2 deletions(-)

diff --git a/src/conf/virstorageobj.c b/src/conf/virstorageobj.c
index bdb167e9e2..9abcac479e 100644
--- a/src/conf/virstorageobj.c
+++ b/src/conf/virstorageobj.c
@@ -86,6 +86,7 @@ struct _virStoragePoolObj {
     char *configFile;
     char *autostartLink;
     bool active;
+    bool starting;
     bool autostart;
     unsigned int asyncjobs;
 
@@ -312,6 +313,21 @@ virStoragePoolObjSetActive(virStoragePoolObjPtr obj,
 }
 
 
+void
+virStoragePoolObjSetStarting(virStoragePoolObjPtr obj,
+                             bool starting)
+{
+    obj->starting = starting;
+}
+
+
+bool
+virStoragePoolObjIsStarting(virStoragePoolObjPtr obj)
+{
+    return obj->starting;
+}
+
+
 bool
 virStoragePoolObjIsAutostart(virStoragePoolObjPtr obj)
 {
@@ -1090,6 +1106,13 @@ virStoragePoolObjIsDuplicate(virStoragePoolObjListPtr pools,
                                obj->def->name);
                 goto cleanup;
             }
+
+            if (virStoragePoolObjIsStarting(obj)) {
+                virReportError(VIR_ERR_OPERATION_INVALID,
+                               _("pool '%s' is starting up"),
+                               obj->def->name);
+                goto cleanup;
+            }
         }
 
         VIR_STEAL_PTR(*objRet, obj);
@@ -1510,7 +1533,8 @@ virStoragePoolObjAssignDef(virStoragePoolObjPtr obj,
                            virStoragePoolDefPtr def,
                            unsigned int flags)
 {
-    if (virStoragePoolObjIsActive(obj)) {
+    if (virStoragePoolObjIsActive(obj) ||
+        virStoragePoolObjIsStarting(obj)) {
         virStoragePoolDefFree(obj->newDef);
         obj->newDef = def;
     } else {
diff --git a/src/conf/virstorageobj.h b/src/conf/virstorageobj.h
index df699a84c5..7dfdf42b26 100644
--- a/src/conf/virstorageobj.h
+++ b/src/conf/virstorageobj.h
@@ -92,6 +92,12 @@ void
 virStoragePoolObjSetActive(virStoragePoolObjPtr obj,
                            bool active);
 
+void
+virStoragePoolObjSetStarting(virStoragePoolObjPtr obj,
+                             bool starting);
+bool
+virStoragePoolObjIsStarting(virStoragePoolObjPtr obj);
+
 bool
 virStoragePoolObjIsAutostart(virStoragePoolObjPtr obj);
 
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 8fb366d218..243e3179cf 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -1196,6 +1196,7 @@ virStoragePoolObjGetVolumesCount;
 virStoragePoolObjIncrAsyncjobs;
 virStoragePoolObjIsActive;
 virStoragePoolObjIsAutostart;
+virStoragePoolObjIsStarting;
 virStoragePoolObjListAdd;
 virStoragePoolObjListExport;
 virStoragePoolObjListForEach;
@@ -1214,6 +1215,7 @@ virStoragePoolObjSetActive;
 virStoragePoolObjSetAutostart;
 virStoragePoolObjSetConfigFile;
 virStoragePoolObjSetDef;
+virStoragePoolObjSetStarting;
 virStoragePoolObjVolumeGetNames;
 virStoragePoolObjVolumeListExport;
 
diff --git a/src/storage/storage_driver.c b/src/storage/storage_driver.c
index def4123b82..60bfa48e25 100644
--- a/src/storage/storage_driver.c
+++ b/src/storage/storage_driver.c
@@ -201,12 +201,14 @@ storageDriverAutostartCallback(virStoragePoolObjPtr obj,
 
     if (virStoragePoolObjIsAutostart(obj) &&
         !virStoragePoolObjIsActive(obj)) {
+
+        virStoragePoolObjSetStarting(obj, true);
         if (backend->startPool &&
             backend->startPool(obj) < 0) {
             virReportError(VIR_ERR_INTERNAL_ERROR,
                            _("Failed to autostart storage pool '%s': %s"),
                            def->name, virGetLastErrorMessage());
-            return;
+            goto cleanup;
         }
         started = true;
     }
@@ -225,6 +227,13 @@ storageDriverAutostartCallback(virStoragePoolObjPtr obj,
             virStoragePoolObjSetActive(obj, true);
         }
     }
+
+ cleanup:
+    if (virStoragePoolObjIsStarting(obj)) {
+        if (!virStoragePoolObjIsActive(obj))
+            virStoragePoolUpdateInactive(obj);
+        virStoragePoolObjSetStarting(obj, false);
+    }
 }
 
 
@@ -750,6 +759,8 @@ storagePoolCreateXML(virConnectPtr conn,
     newDef = NULL;
     def = virStoragePoolObjGetDef(obj);
 
+    virStoragePoolObjSetStarting(obj, true);
+
     if (backend->buildPool) {
         if (flags & VIR_STORAGE_POOL_CREATE_WITH_BUILD_OVERWRITE)
             build_flags |= VIR_STORAGE_POOL_BUILD_OVERWRITE;
@@ -786,6 +797,11 @@ storagePoolCreateXML(virConnectPtr conn,
     pool = virGetStoragePool(conn, def->name, def->uuid, NULL, NULL);
 
  cleanup:
+    if (virStoragePoolObjIsStarting(obj)) {
+        if (!virStoragePoolObjIsActive(obj))
+            virStoragePoolUpdateInactive(obj);
+        virStoragePoolObjSetStarting(obj, false);
+    }
     virObjectEventStateQueue(driver->storageEventState, event);
     virStoragePoolObjEndAPI(&obj);
     return pool;
@@ -937,6 +953,8 @@ storagePoolCreate(virStoragePoolPtr pool,
         goto cleanup;
     }
 
+    virStoragePoolObjSetStarting(obj, true);
+
     if (backend->buildPool) {
         if (flags & VIR_STORAGE_POOL_CREATE_WITH_BUILD_OVERWRITE)
             build_flags |= VIR_STORAGE_POOL_BUILD_OVERWRITE;
@@ -972,6 +990,11 @@ storagePoolCreate(virStoragePoolPtr pool,
     ret = 0;
 
  cleanup:
+    if (virStoragePoolObjIsStarting(obj)) {
+        if (!virStoragePoolObjIsActive(obj))
+            virStoragePoolUpdateInactive(obj);
+        virStoragePoolObjSetStarting(obj, false);
+    }
     virObjectEventStateQueue(driver->storageEventState, event);
     virStoragePoolObjEndAPI(&obj);
     return ret;
@@ -1004,6 +1027,8 @@ storagePoolBuild(virStoragePoolPtr pool,
         goto cleanup;
     }
 
+    virStoragePoolObjSetStarting(obj, true);
+
     if (backend->buildPool &&
         backend->buildPool(obj, flags) < 0)
         goto cleanup;
@@ -1016,6 +1041,10 @@ storagePoolBuild(virStoragePoolPtr pool,
     ret = 0;
 
  cleanup:
+    if (virStoragePoolObjIsStarting(obj)) {
+        virStoragePoolUpdateInactive(obj);
+        virStoragePoolObjSetStarting(obj, false);
+    }
     virObjectEventStateQueue(driver->storageEventState, event);
     virStoragePoolObjEndAPI(&obj);
     return ret;
-- 
2.21.0