[Qemu-devel] [PULL 1/3] Qemu/Xen: Fix early freeing MSIX MMIO memory region

[Stefano Stabellini <stefano.stabellini@eu.citrix.com>]

From: Lan Tianyu <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>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
---
 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;
-- 
1.7.10.4