Re: [Qemu-devel] [PATCH] spapr: fix potential memory leak in spapr_core_plug()

[Bharata B Rao <bharata@linux.vnet.ibm.com>]

On Wed, Jul 12, 2017 at 11:48:39AM +0200, Greg Kurz wrote:
> Since commit 5c1da81215c7 ("spapr: Remove unnecessary differences between
> hotplug and coldplug paths"), the CPU DT for the DRC is always allocated.
> This causes a memory leak for pseries-2.6 and older machine types, that
> don't support CPU hotplug and don't allocate DRCs for CPUs.
> 
> Reported-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> Signed-off-by: Greg Kurz <groug@kaod.org>
> ---
>  hw/ppc/spapr.c |    9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 12b3f099d4c9..4a480e1c1dd9 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -2993,8 +2993,6 @@ static void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
>      CPUState *cs = CPU(core->threads);
>      sPAPRDRConnector *drc;
>      Error *local_err = NULL;
> -    void *fdt = NULL;
> -    int fdt_offset = 0;
>      int smt = kvmppc_smt_threads();
>      CPUArchId *core_slot;
>      int index;
> @@ -3009,9 +3007,12 @@ static void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
> 
>      g_assert(drc || !mc->has_hotpluggable_cpus);
> 
> -    fdt = spapr_populate_hotplug_cpu_dt(cs, &fdt_offset, spapr);
> -
>      if (drc) {
> +        void *fdt;
> +        int fdt_offset;
> +
> +        fdt = spapr_populate_hotplug_cpu_dt(cs, &fdt_offset, spapr);
> +
>          spapr_drc_attach(drc, dev, fdt, fdt_offset, &local_err);
>          if (local_err) {
>              g_free(fdt);

You say this in the patch description already, but want to note explicitly
that this prevents double allocation for pseries-2.6 and ealier types and
not for newer machine types.

Regards,
Bharata.