[PATCH v3 2/6] libvhost-user: Add vu_add_mem_reg input validation

[Raphael Norwitz <raphael.norwitz@nutanix.com>]

Today if multiple FDs are sent from the VMM to the backend in a
VHOST_USER_ADD_MEM_REG message, one FD will be mapped and the remaining
FDs will be leaked. Therefore if multiple FDs are sent we report an
error and fail the operation, closing all FDs in the message.

Likewise in case the VMM sends a message with a size less than that
of a memory region descriptor, we add a check to gracefully report an
error and fail the operation rather than crashing.

Signed-off-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
---
 subprojects/libvhost-user/libvhost-user.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
index b09b1c269e..1a8fc9d600 100644
--- a/subprojects/libvhost-user/libvhost-user.c
+++ b/subprojects/libvhost-user/libvhost-user.c
@@ -690,6 +690,21 @@ vu_add_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
     VuDevRegion *dev_region = &dev->regions[dev->nregions];
     void *mmap_addr;
 
+    if (vmsg->fd_num != 1) {
+        vmsg_close_fds(vmsg);
+        vu_panic(dev, "VHOST_USER_ADD_MEM_REG received %d fds - only 1 fd "
+                      "should be sent for this message type", vmsg->fd_num);
+        return false;
+    }
+
+    if (vmsg->size < VHOST_USER_MEM_REG_SIZE) {
+        close(vmsg->fds[0]);
+        vu_panic(dev, "VHOST_USER_ADD_MEM_REG requires a message size of at "
+                      "least %d bytes and only %d bytes were received",
+                      VHOST_USER_MEM_REG_SIZE, vmsg->size);
+        return false;
+    }
+
     /*
      * If we are in postcopy mode and we receive a u64 payload with a 0 value
      * we know all the postcopy client bases have been received, and we
-- 
2.20.1