VMCI: Fix integer overflow in VMCI handle arrays

commit 1c2eb5b2853c9f513690ba6b71072d8eb65da16a upstream.

The VMCI handle array has an integer overflow in
vmci_handle_arr_append_entry when it tries to expand the array. This can be
triggered from a guest, since the doorbell link hypercall doesn't impose a
limit on the number of doorbell handles that a VM can create in the
hypervisor, and these handles are stored in a handle array.

In this change, we introduce a mandatory max capacity for handle
arrays/lists to avoid excessive memory usage.

Signed-off-by: Vishnu Dasa <vdasa@vmware.com>
Reviewed-by: Adit Ranadive <aditr@vmware.com>
Reviewed-by: Jorgen Hansen <jhansen@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

1 files changed, 10 insertions, 1 deletions

diff --git a/include/linux/vmw_vmci_defs.h b/include/linux/vmw_vmci_defs.h
index 65ac54c61c18..7023432013e8 100644
--- a/include/linux/vmw_vmci_defs.h
+++ b/include/linux/vmw_vmci_defs.h
@@ -75,9 +75,18 @@ enum {
 
 /*
  * A single VMCI device has an upper limit of 128MB on the amount of
- * memory that can be used for queue pairs.
+ * memory that can be used for queue pairs. Since each queue pair
+ * consists of at least two pages, the memory limit also dictates the
+ * number of queue pairs a guest can create.
  */
 #define VMCI_MAX_GUEST_QP_MEMORY (128 * 1024 * 1024)
+#define VMCI_MAX_GUEST_QP_COUNT  (VMCI_MAX_GUEST_QP_MEMORY / PAGE_SIZE / 2)
+
+/*
+ * There can be at most PAGE_SIZE doorbells since there is one doorbell
+ * per byte in the doorbell bitmap page.
+ */
+#define VMCI_MAX_GUEST_DOORBELL_COUNT PAGE_SIZE
 
 /*
  * Queues with pre-mapped data pages must be small, so that we don't pin