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

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(a)redhat.com&gt; --- 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/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;