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

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 12 Oct 2015, Paolo Bonzini wrote:
> On 12/10/2015 13:09, Stefano Stabellini wrote:
> > On Sun, 11 Oct 2015, Lan Tianyu wrote:
> >> From: <tianyu.lan@xxxxxxxxx>>
> >>
> >> 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@xxxxxxxxx>
> > 
> > Looks good to me. Paolo?
> 
> Also looks good to me.  Thanks!

I'll add it to my tree.



> >>  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
> >>
> 

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