virt: acrn: Prefer array_size and struct_size over open coded arithmetic

As noted in the "Deprecated Interfaces, Language Features, Attributes,
and Conventions" documentation [1], size calculations (especially
multiplication) should not be performed in memory allocator (or similar)
function arguments due to the risk of them overflowing. This could lead
to values wrapping around and a smaller allocation being made than the
caller was expecting. Using those allocations could lead to linear
overflows of heap memory and other misbehaviors.

So, use the array_size() helper to do the arithmetic instead of the
argument "count * size" in the vzalloc() function.

Also, take the opportunity to add a flexible array member of struct
vm_memory_region_op to the vm_memory_region_batch structure. And then,
change the code accordingly and use the struct_size() helper to do the
arithmetic instead of the argument "size + size * count" in the kzalloc
function.

This code was detected with the help of Coccinelle and audited and fixed
manually.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments

Acked-by: Fei Li <fei1.li@intel.com>
Signed-off-by: Len Baker <len.baker@gmx.com>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

1 files changed, 6 insertions, 4 deletions

diff --git a/drivers/virt/acrn/acrn_drv.h b/drivers/virt/acrn/acrn_drv.h
index 1be54efa666c..5663c17ad37c 100644
--- a/drivers/virt/acrn/acrn_drv.h
+++ b/drivers/virt/acrn/acrn_drv.h
@@ -48,6 +48,7 @@ struct vm_memory_region_op {
  * @reserved:		Reserved.
  * @regions_num:	The number of vm_memory_region_op.
  * @regions_gpa:	Physical address of a vm_memory_region_op array.
+ * @regions_op:		Flexible array of vm_memory_region_op.
  *
  * HC_VM_SET_MEMORY_REGIONS uses this structure to manage EPT mappings of
  * multiple memory regions of a User VM. A &struct vm_memory_region_batch
@@ -55,10 +56,11 @@ struct vm_memory_region_op {
  * ACRN Hypervisor.
  */
 struct vm_memory_region_batch {
-	u16	vmid;
-	u16	reserved[3];
-	u32	regions_num;
-	u64	regions_gpa;
+	u16			   vmid;
+	u16			   reserved[3];
+	u32			   regions_num;
+	u64			   regions_gpa;
+	struct vm_memory_region_op regions_op[];
 };
 
 /**