Re: [libvirt] [PATCH 4/4] qemu: Obtain reference on monConfig

On Fri, Apr 06, 2018 at 06:53 PM +0200, John Ferlan <jferlan(a)redhat.com&gt; wrote: > Because we allow a QEMU_JOB_DESTROY to occur while we're starting > up and we drop the @vm lock prior to qemuMonitorOpen, it's possible > that a domain destroy operation "wins" the race, calls qemuProcessStop > which will free and reinitialize priv->monConfig. Depending on the > exact timing either qemuMonitorOpen will be passed a NULL @config > variable or it will be using free'd (and possibly reclaimed) memory > as the @config parameter - neither of which is good. > > Resolve this by localizing the @monConfig, taking an extra reference, > and then once we get the @vm lock again removing our reference since > we are done with it. > > Signed-off-by: John Ferlan <jferlan(a)redhat.com&gt; > --- > src/qemu/qemu_process.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c > index a8dab92dd6..988c6b1537 100644 > --- a/src/qemu/qemu_process.c > +++ b/src/qemu/qemu_process.c > @@ -1776,6 +1776,7 @@ qemuConnectMonitor(virQEMUDriverPtr driver, virDomainObjPtr vm, int asyncJob, > qemuDomainObjPrivatePtr priv = vm->privateData; > qemuMonitorPtr mon = NULL; > unsigned long long timeout = 0; > + virDomainChrSourceDefPtr monConfig; > > if (qemuSecuritySetDaemonSocketLabel(driver->securityManager, vm->def) < 0) { > VIR_ERROR(_("Failed to set security context for monitor for %s"), > @@ -1794,10 +1795,12 @@ qemuConnectMonitor(virQEMUDriverPtr driver, virDomainObjPtr vm, int asyncJob, > virObjectRef(vm); > > ignore_value(virTimeMillisNow(&priv->monStart)); > + monConfig = priv->monConfig; > + virObjectRef(monConfig); > virObjectUnlock(vm); > > mon = qemuMonitorOpen(vm, > - priv->monConfig, > + monConfig, > priv->monJSON, > timeout, > &monitorCallbacks, > @@ -1813,6 +1816,7 @@ qemuConnectMonitor(virQEMUDriverPtr driver, virDomainObjPtr vm, int asyncJob, > > virObjectLock(vm); > virObjectUnref(vm); > + virObjectUnref(monConfig); Only for consistency: I would first unref @monConfig and then do the unref for @vm.

> priv->monStart = 0; > > if (!virDomainObjIsActive(vm)) { > -- > 2.13.6 > > -- > libvir-list mailing list > libvir-list(a)redhat.com > https://www.redhat.com/mailman/listinfo/libvir-list > -- Beste Grüße / Kind regards Marc Hartmayer IBM Deutschland Research & Development GmbH Vorsitzende des Aufsichtsrats: Martina Koederitz Geschäftsführung: Dirk Wittkopp Sitz der Gesellschaft: Böblingen Registergericht: Amtsgericht Stuttgart, HRB 243294