[PATCH] hw/pvrdma: Protect against buggy or malicious guest driver

[Yuval Shaia <yuval.shaia.ml@gmail.com>]

Guest driver might execute HW commands when shared buffers are not yet
allocated.
This might happen on purpose (malicious guest) or because some other
guest/host address mapping.
We need to protect againts such case.

Reported-by: Mauro Matteo Cascella <mcascell@redhat.com>
Signed-off-by: Yuval Shaia <yuval.shaia.ml@gmail.com>
---
 hw/rdma/vmw/pvrdma_cmd.c  | 6 ++++++
 hw/rdma/vmw/pvrdma_main.c | 9 +++++----
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/hw/rdma/vmw/pvrdma_cmd.c b/hw/rdma/vmw/pvrdma_cmd.c
index da7ddfa548..89db963c46 100644
--- a/hw/rdma/vmw/pvrdma_cmd.c
+++ b/hw/rdma/vmw/pvrdma_cmd.c
@@ -796,6 +796,12 @@ int pvrdma_exec_cmd(PVRDMADev *dev)
 
     dsr_info = &dev->dsr_info;
 
+    if (!dsr_info->dsr) {
+            /* Buggy or malicious guest driver */
+            rdma_error_report("Exec command without dsr, req or rsp buffers");
+            goto out;
+    }
+
     if (dsr_info->req->hdr.cmd >= sizeof(cmd_handlers) /
                       sizeof(struct cmd_handler)) {
         rdma_error_report("Unsupported command");
diff --git a/hw/rdma/vmw/pvrdma_main.c b/hw/rdma/vmw/pvrdma_main.c
index 91206dbb8e..aae382af59 100644
--- a/hw/rdma/vmw/pvrdma_main.c
+++ b/hw/rdma/vmw/pvrdma_main.c
@@ -159,13 +159,13 @@ static void free_dsr(PVRDMADev *dev)
     free_dev_ring(pci_dev, &dev->dsr_info.cq, dev->dsr_info.cq_ring_state);
 
     rdma_pci_dma_unmap(pci_dev, dev->dsr_info.req,
-                         sizeof(union pvrdma_cmd_req));
+                       sizeof(union pvrdma_cmd_req));
 
     rdma_pci_dma_unmap(pci_dev, dev->dsr_info.rsp,
-                         sizeof(union pvrdma_cmd_resp));
+                       sizeof(union pvrdma_cmd_resp));
 
     rdma_pci_dma_unmap(pci_dev, dev->dsr_info.dsr,
-                         sizeof(struct pvrdma_device_shared_region));
+                       sizeof(struct pvrdma_device_shared_region));
 
     dev->dsr_info.dsr = NULL;
 }
@@ -249,7 +249,8 @@ static void init_dsr_dev_caps(PVRDMADev *dev)
 {
     struct pvrdma_device_shared_region *dsr;
 
-    if (dev->dsr_info.dsr == NULL) {
+    if (!dev->dsr_info.dsr) {
+        /* Buggy or malicious guest driver */
         rdma_error_report("Can't initialized DSR");
         return;
     }
-- 
2.20.1