Re: [Qemu-devel] [PATCH] Qemu/Xen: Fix early freeing MSIX MMIO memory region

[Paolo Bonzini <pbonzini@redhat.com>]

On 12/10/2015 13:09, Stefano Stabellini wrote:
> On Sun, 11 Oct 2015, Lan Tianyu wrote:
>> From: <tianyu.lan@intel.com>>
>>
>> msix->mmio is added to XenPCIPassthroughState's object as property.
>> object_finalize_child_property is called for XenPCIPassthroughState's
>> object, which calls object_property_del_all, which is going to try to
>> delete msix->mmio. object_finalize_child_property() will access
>> msix->mmio's obj. But the whole msix struct has already been freed
>> by xen_pt_msix_delete. This will cause segment fault when msix->mmio
>> has been overwritten.
>>
>> This patch is to fix the issue.
>>
>> Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
> 
> Looks good to me. Paolo?

Also looks good to me.  Thanks!

Paolo

>>  hw/xen/xen_pt.c             |    8 ++++++++
>>  hw/xen/xen_pt.h             |    1 +
>>  hw/xen/xen_pt_config_init.c |    2 +-
>>  hw/xen/xen_pt_msi.c         |   13 ++++++++++++-
>>  4 files changed, 22 insertions(+), 2 deletions(-)
>>
>> diff --git a/hw/xen/xen_pt.c b/hw/xen/xen_pt.c
>> index 2b54f52..aa96288 100644
>> --- a/hw/xen/xen_pt.c
>> +++ b/hw/xen/xen_pt.c
>> @@ -938,10 +938,18 @@ static void xen_pci_passthrough_class_init(ObjectClass *klass, void *data)
>>      dc->props = xen_pci_passthrough_properties;
>>  };
>>  
>> +static void xen_pci_passthrough_finalize(Object *obj)
>> +{
>> +    XenPCIPassthroughState *s = XEN_PT_DEVICE(obj);
>> +
>> +    xen_pt_msix_delete(s);
>> +}
>> +
>>  static const TypeInfo xen_pci_passthrough_info = {
>>      .name = TYPE_XEN_PT_DEVICE,
>>      .parent = TYPE_PCI_DEVICE,
>>      .instance_size = sizeof(XenPCIPassthroughState),
>> +    .instance_finalize = xen_pci_passthrough_finalize,
>>      .class_init = xen_pci_passthrough_class_init,
>>  };
>>  
>> diff --git a/hw/xen/xen_pt.h b/hw/xen/xen_pt.h
>> index 3bc22eb..c545280 100644
>> --- a/hw/xen/xen_pt.h
>> +++ b/hw/xen/xen_pt.h
>> @@ -305,6 +305,7 @@ void xen_pt_msi_disable(XenPCIPassthroughState *s);
>>  
>>  int xen_pt_msix_init(XenPCIPassthroughState *s, uint32_t base);
>>  void xen_pt_msix_delete(XenPCIPassthroughState *s);
>> +void xen_pt_msix_unmap(XenPCIPassthroughState *s);
>>  int xen_pt_msix_update(XenPCIPassthroughState *s);
>>  int xen_pt_msix_update_remap(XenPCIPassthroughState *s, int bar_index);
>>  void xen_pt_msix_disable(XenPCIPassthroughState *s);
>> diff --git a/hw/xen/xen_pt_config_init.c b/hw/xen/xen_pt_config_init.c
>> index 4a5bc11..0efee11 100644
>> --- a/hw/xen/xen_pt_config_init.c
>> +++ b/hw/xen/xen_pt_config_init.c
>> @@ -2079,7 +2079,7 @@ void xen_pt_config_delete(XenPCIPassthroughState *s)
>>  
>>      /* free MSI/MSI-X info table */
>>      if (s->msix) {
>> -        xen_pt_msix_delete(s);
>> +        xen_pt_msix_unmap(s);
>>      }
>>      g_free(s->msi);
>>  
>> diff --git a/hw/xen/xen_pt_msi.c b/hw/xen/xen_pt_msi.c
>> index e3d7194..82de2bc 100644
>> --- a/hw/xen/xen_pt_msi.c
>> +++ b/hw/xen/xen_pt_msi.c
>> @@ -610,7 +610,7 @@ error_out:
>>      return rc;
>>  }
>>  
>> -void xen_pt_msix_delete(XenPCIPassthroughState *s)
>> +void xen_pt_msix_unmap(XenPCIPassthroughState *s)
>>  {
>>      XenPTMSIX *msix = s->msix;
>>  
>> @@ -627,6 +627,17 @@ void xen_pt_msix_delete(XenPCIPassthroughState *s)
>>      }
>>  
>>      memory_region_del_subregion(&s->bar[msix->bar_index], &msix->mmio);
>> +}
>> +
>> +void xen_pt_msix_delete(XenPCIPassthroughState *s)
>> +{
>> +    XenPTMSIX *msix = s->msix;
>> +
>> +    if (!msix) {
>> +        return;
>> +    }
>> +
>> +    object_unparent(OBJECT(&msix->mmio));
>>  
>>      g_free(s->msix);
>>      s->msix = NULL;
>> -- 
>> 1.7.9.5
>>