[PATCH] hw/virtio/virtio-pci: add defensive check for vector_irqfd

[gerben]

From: Denis Rastyogin <ger...@altlinux.org>

Add a NULL check for proxy->vector_irqfd in
virtio_pci_one_vector_unmask() before taking the irqfd path.
This prevents potential access to uninitialized state if
vector_irqfd is absent.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Reported-by: Alexey Appolonov <ale...@altlinux.org>
Signed-off-by: Denis Rastyogin <ger...@altlinux.org>
---
 hw/virtio/virtio-pci.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index 767216d795..07904f6f9b 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -1015,7 +1015,11 @@ static int virtio_pci_one_vector_unmask(VirtIOPCIProxy 
*proxy,
             event_notifier_set(n);
         }
     } else {
-        ret = kvm_virtio_pci_irqfd_use(proxy, n, vector);
+        if (proxy->vector_irqfd) {
+            ret = kvm_virtio_pci_irqfd_use(proxy, n, vector);
+        } else {
+            ret = -EFAULT;
+        }
     }
     return ret;
 }
-- 
2.42.2