Re: [Qemu-devel] [PATCH] spapr: fix core unplug crash

[David Gibson <david@gibson.dropbear.id.au>]

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On Fri, Jul 08, 2016 at 03:12:07PM +0200, Greg Kurz wrote:
> If the host has 8 threads/core and the guest is started with:
> 
> -smp cores=1,threads=4,maxcpus=12
> 
> It is possible to crash QEMU by doing:
> 
> (qemu) device_add host-spapr-cpu-core,core-id=16,id=foo
> (qemu) device_del foo
> Segmentation fault
> 
> This is caused because spapr_core_unplug() assumes cpu_dt_id == core_id.
> Even if it happens to be the case when the host and guest have the same
> number of threads per core, it is conceptually wrong and we may pass a
> bogus id to spapr_dr_connector_by_id() and spapr_core_release() crashes.
> 
> Let's use cc->core_id, which is the id that was used to create th DR
> connector.
> 
> Signed-off-by: Greg Kurz <groug@kaod.org>

Thanks,  applied to ppc-for-2.7.

> ---
>  hw/ppc/spapr_cpu_core.c |    6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
> index 70b6b0b5ee17..106eaf45b399 100644
> --- a/hw/ppc/spapr_cpu_core.c
> +++ b/hw/ppc/spapr_cpu_core.c
> @@ -126,11 +126,9 @@ static void spapr_core_release(DeviceState *dev, void *opaque)
>  void spapr_core_unplug(HotplugHandler *hotplug_dev, DeviceState *dev,
>                         Error **errp)
>  {
> -    sPAPRCPUCore *core = SPAPR_CPU_CORE(OBJECT(dev));
> -    PowerPCCPU *cpu = POWERPC_CPU(core->threads);
> -    int id = ppc_get_vcpu_dt_id(cpu);
> +    CPUCore *cc = CPU_CORE(dev);
>      sPAPRDRConnector *drc =
> -        spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_CPU, id);
> +        spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_CPU, cc->core_id);
>      sPAPRDRConnectorClass *drck;
>      Error *local_err = NULL;
>  
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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