When commit 96b7af4388b3 intoduced a .instance_finalize() handler,
it did not take into account that the container was not necessarily
inserted into the container list of the address space. Hence, if
the container object is destroyed, by calling object_unref() for
example, before vfio_address_space_insert() is called, QEMU may
crash when removing the container from the list as done in
vfio_container_instance_finalize(). This was seen with an SEV-SNP
guest for which discarding of RAM fails.

To resolve this issue, use the safe version of QLIST_REMOVE().

Cc: Zhenzhong Duan <zhenzhong.duan@intel.com>
Cc: Eric Auger <eric.auger@redhat.com>
Fixes: 96b7af4388b3 ("vfio/container: Move vfio_container_destroy() to an instance_finalize() handler")
Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
---
 hw/vfio/container-base.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/vfio/container-base.c b/hw/vfio/container-base.c
index 809b15767425a48f2404b08fc409ee5684af2094..6f86c37d971ec38426dacd471bca837c0d0df806 100644
--- a/hw/vfio/container-base.c
+++ b/hw/vfio/container-base.c
@@ -103,7 +103,7 @@ static void vfio_container_instance_finalize(Object *obj)
     VFIOContainerBase *bcontainer = VFIO_IOMMU(obj);
     VFIOGuestIOMMU *giommu, *tmp;
 
-    QLIST_REMOVE(bcontainer, next);
+    QLIST_SAFE_REMOVE(bcontainer, next);
 
     QLIST_FOREACH_SAFE(giommu, &bcontainer->giommu_list, giommu_next, tmp) {
         memory_region_unregister_iommu_notifier(
-- 
2.47.0

Michael,

On 11/18/24 09:37, Cédric Le Goater wrote:
> When commit 96b7af4388b3 intoduced a .instance_finalize() handler,
> it did not take into account that the container was not necessarily
> inserted into the container list of the address space. Hence, if
> the container object is destroyed, by calling object_unref() for
> example, before vfio_address_space_insert() is called, QEMU may
> crash when removing the container from the list as done in
> vfio_container_instance_finalize(). This was seen with an SEV-SNP
> guest for which discarding of RAM fails.
> 
> To resolve this issue, use the safe version of QLIST_REMOVE().
> 
> Cc: Zhenzhong Duan <zhenzhong.duan@intel.com>
> Cc: Eric Auger <eric.auger@redhat.com>
> Fixes: 96b7af4388b3 ("vfio/container: Move vfio_container_destroy() to an instance_finalize() handler")
> Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> Signed-off-by: Cédric Le Goater <clg@redhat.com>

This is 9.1 material.

Thanks,

C.

18.11.2024 18:02, Cédric Le Goater wrote:
> Michael,
> 
> On 11/18/24 09:37, Cédric Le Goater wrote:
>> When commit 96b7af4388b3 intoduced a .instance_finalize() handler,
>> it did not take into account that the container was not necessarily
>> inserted into the container list of the address space. Hence, if
>> the container object is destroyed, by calling object_unref() for
>> example, before vfio_address_space_insert() is called, QEMU may
>> crash when removing the container from the list as done in
>> vfio_container_instance_finalize(). This was seen with an SEV-SNP
>> guest for which discarding of RAM fails.
>>
>> To resolve this issue, use the safe version of QLIST_REMOVE().
>>
>> Cc: Zhenzhong Duan <zhenzhong.duan@intel.com>
>> Cc: Eric Auger <eric.auger@redhat.com>
>> Fixes: 96b7af4388b3 ("vfio/container: Move vfio_container_destroy() to an instance_finalize() handler")
>> Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
>> Signed-off-by: Cédric Le Goater <clg@redhat.com>
> 
> This is 9.1 material.
Thank you for letting me know, queued up!

/mjt