[PATCH] hw/vfio/pci: fix double free in vfio_msi_disable

[Evgeny Yakovlev <wrfsh@yandex-team.ru>]

The following guest behaviour patter leads to double free in VFIO PCI:

1. Guest enables MSI interrupts
vfio_msi_enable is called, but fails in vfio_enable_vectors.
In our case this was because VFIO GPU device was in D3 state.
Unhappy path in vfio_msi_enable will g_free(vdev->msi_vectors) but not
set this pointer to NULL

2. Guest still sees MSI an enabled after that because emulated config
write is done in vfio_pci_write_config unconditionally before calling
vfio_msi_enable

3. Guest disables MSI interrupts
vfio_msi_disable is called and tries to g_free(vdev->msi_vectors)
in vfio_msi_disable_common => double free

Signed-off-by: Evgeny Yakovlev <wrfsh@yandex-team.ru>
---
 hw/vfio/pci.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index c5e6fe6..12fac39 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -651,6 +651,7 @@ retry:
         }
 
         g_free(vdev->msi_vectors);
+        vdev->msi_vectors = NULL;
 
         if (ret > 0 && ret != vdev->nr_vectors) {
             vdev->nr_vectors = ret;
-- 
2.7.4