On Tue, Aug 02, 2016 at 02:20:51 +0000, weifuqiang wrote:
[PATCH] qemu: fix libvirtd crash in migration after vm shutdown
If we shutdown a guest, then migrate it without the arg XML, libvirtd will get crashed.
The reason is that:
1 during shutdown callback, qemuProcessStop() , it points vm->def to vm->newDef
2 during migration, it frees persistentDef, which points to vm->newDef when the arg XML is NULL.
However, because vm->newDef is now vm->def, what we IN FACT freed is vm->def.
3 it will refer to vm->def after step2, thus invalid read/write causes libvirtd crash
We needn't to free persistentDef if persist_xml is NULL, because no extra def was alloced if persistent_xml is NULL.
--- src/qemu/qemu_migration.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c index 6a683f7..3636c93 100644 --- a/src/qemu/qemu_migration.c +++ b/src/qemu/qemu_migration.c @@ -4915,7 +4915,7 @@ qemuMigrationRun(virQEMUDriverPtr driver, VIR_WARN("Unable to encode migration cookie"); } - if (persistDef != vm->newDef) + if (persist_xml && persistDef) virDomainDefFree(persistDef); qemuMigrationCookieFree(mig);
If persist_xml != NULL then persistDef is it's parsed version (or NULL) and we need to free it. Otherwise it's just a copy of another pointer. In other words, your patch is correct (although checking for persist_xml is enough). An alternative solution would be to make sure we can always free persistDef by making a copy of vm->newDef rather than copying just the pointer and free it unconditionally. Anyway, your patch is good enough. ACK. I'll push it later. Jirka