fix: prevent integer overflow in 32-bit binaries when configuring virtual disk

[spacegospod]

Description

Virtual disk sizes are passed to the API in bytes during VM reconfiguration. This means that sizes in excess of 2GB will overflow a signed 32-bit integer.

In golang the default int type's size is dependent on the OS. This means that trying to add a virtual disk larger than 2GB while cloning a VM and running a 32-bit version of the provider will cause an overflow.

The bindings that we use to call the API use int64 which means that the problem is in the provider and not in govmomi.

The actual conversion looks like this:

disk.CapacityInBytes = structure.GiBToByte(ns.(int))

The bug is caused by GiBToByte which overflows internally and hides the problem.

func GiBToByte(n interface{}) int64 {
	switch v := n.(type) {
	case int:
		return int64(v * int(math.Pow(1024, 3)))
	case int32:
		return int64(v * int32(math.Pow(1024, 3)))
	case int64:
		return v * int64(math.Pow(1024, 3))
	}
	panic(fmt.Errorf("non-integer type %T for value", n))
}

We end up in the 1st case. The integer cast in the brackets is effectively a int32 cast since we run on a 32bit OS.

This causes the overflow.

To fix this I am modifying the call to GiBToByte by passing the parameter as int64 which forces the function to go through the 64bit case.

Acceptance tests

• Have you added an acceptance test for the functionality being added?
• Have you run the acceptance tests on this branch?

Ran TestAccResourceVSphereVirtualMachine_cloneFromTemplate and TestAccResourceVSphereVirtualMachine_basic just to make sure there are no obvious regressions

• Prepared Terraform on a 32bit win10 VM
• Created a configuration that reproduces the bug by cloning a VM and adding a 100GB disk
• Recompiled the provider with the fix and configured a local override on the VM
• Verified that the same configuration works as expected

Release Note

Release note for CHANGELOG:

NONE

References

Closes #2116
CLoses #1578

[tenthirtyam]

Nice fix!

I added an update to the CHANGELOG tagging this under v2.8.2.

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