Re: [PATCH 1/1] Drivers: hv: vmbus: Fail VMBus module init for non-nested root partition

[Easwar Hariharan]

On 8/4/2026 12:05, Michael Kelley wrote:
> The VMBus module should not be loaded when Linux is running directly
> in the root partition and root is not nested in another VM. Current
> code checks this condition and skips VMBus module initialization, which
> works. But it returns 0 as the result, so Linux thinks the module has
> successfully loaded. Later, if the module were to be unloaded, the
> VMBus module unload code tries to clean up things that were never
> initialized, resulting in memory faults and a panic.
> 
> Fix this by having VMBus module initialization return -ENODEV for this
> case. The module is then not loaded, and the unload path can never run.
> 
> Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
> Closes: https://lore.kernel.org/linux-hyperv/20260721154943.A09BD1F00A3D@xxxxxxxxxxxxxxx/
> Fixes: 7e279d78664aa ("Drivers: hv: vmbus: skip VMBus initialization if Linux is root")
> Signed-off-by: Michael Kelley <mhklinux@xxxxxxxxxxx>
> ---
>  drivers/hv/vmbus_drv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index e19ec73b0187..849d7e1a7320 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -2976,7 +2976,7 @@ static int __init hv_acpi_init(void)
>  		return -ENODEV;
>  
>  	if (hv_root_partition() && !hv_nested)
> -		return 0;
> +		return -ENODEV;
>  
>  	/*
>  	 * Get ACPI resources first.

This seems straightforward:


Reviewed-by: Easwar Hariharan <easwar.hariharan@xxxxxxxxxxxxxxxxxxx>