[PATCH 3/4] vfio/container: Fix potential SIGSEGV when recover from unmap-all-vaddr failure

[Zhenzhong Duan <zhenzhong.duan@intel.com>]

cpr.saved_dma_map isn't initialized in source qemu which lead to vioc->dma_map
assigned a NULL value, this will trigger SIGSEGV.

Fix it by save and restore vioc->dma_map locally.

Fixes: eba1f657cbb1 ("vfio/container: recover from unmap-all-vaddr failure")
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
---
 include/hw/vfio/vfio-cpr.h | 8 +++++---
 hw/vfio/cpr-legacy.c       | 3 ++-
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/include/hw/vfio/vfio-cpr.h b/include/hw/vfio/vfio-cpr.h
index 8bf85b9f4e..aef542e93c 100644
--- a/include/hw/vfio/vfio-cpr.h
+++ b/include/hw/vfio/vfio-cpr.h
@@ -16,14 +16,16 @@ struct VFIOContainer;
 struct VFIOContainerBase;
 struct VFIOGroup;
 
+typedef int (*DMA_MAP_FUNC)(const struct VFIOContainerBase *bcontainer,
+                            hwaddr iova, ram_addr_t size, void *vaddr,
+                            bool readonly, MemoryRegion *mr);
+
 typedef struct VFIOContainerCPR {
     Error *blocker;
     bool vaddr_unmapped;
     NotifierWithReturn transfer_notifier;
     MemoryListener remap_listener;
-    int (*saved_dma_map)(const struct VFIOContainerBase *bcontainer,
-                         hwaddr iova, ram_addr_t size,
-                         void *vaddr, bool readonly, MemoryRegion *mr);
+    DMA_MAP_FUNC saved_dma_map;
 } VFIOContainerCPR;
 
 typedef struct VFIODeviceCPR {
diff --git a/hw/vfio/cpr-legacy.c b/hw/vfio/cpr-legacy.c
index a84c3247b7..100a8db74d 100644
--- a/hw/vfio/cpr-legacy.c
+++ b/hw/vfio/cpr-legacy.c
@@ -148,6 +148,7 @@ static int vfio_cpr_fail_notifier(NotifierWithReturn *notifier,
          */
 
         VFIOIOMMUClass *vioc = VFIO_IOMMU_GET_CLASS(bcontainer);
+        DMA_MAP_FUNC saved_dma_map = vioc->dma_map;
         vioc->dma_map = vfio_legacy_cpr_dma_map;
 
         container->cpr.remap_listener = (MemoryListener) {
@@ -158,7 +159,7 @@ static int vfio_cpr_fail_notifier(NotifierWithReturn *notifier,
                                  bcontainer->space->as);
         memory_listener_unregister(&container->cpr.remap_listener);
         container->cpr.vaddr_unmapped = false;
-        vioc->dma_map = container->cpr.saved_dma_map;
+        vioc->dma_map = saved_dma_map;
     }
     return 0;
 }
-- 
2.34.1