Re: [PATCH] mshv: bounds-check cpu index in vtl mmap fault handler

Naman, Saurabh, please review this.

On Thu, Jul 09, 2026 at 10:19:47AM +0800, Yi Xie wrote:
> cpu is taken from pgoff & 0xffff.  cpu_online() does not reject cpu >=
> nr_cpu_ids, and per_cpu_ptr() can then walk off __per_cpu_offset.
> 
> Signed-off-by: Yi Xie <[email protected]>
> ---
>  drivers/hv/mshv_vtl_main.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/hv/mshv_vtl_main.c b/drivers/hv/mshv_vtl_main.c
> index 0d3d4161974f..fc50c44ac1bd 100644
> --- a/drivers/hv/mshv_vtl_main.c
> +++ b/drivers/hv/mshv_vtl_main.c
> @@ -801,7 +801,7 @@ static vm_fault_t mshv_vtl_fault(struct vm_fault *vmf)
>  	int cpu = vmf->pgoff & MSHV_PG_OFF_CPU_MASK;
>  	int real_off = vmf->pgoff >> MSHV_REAL_OFF_SHIFT;
>  
> -	if (!cpu_online(cpu))
> +	if (cpu >= nr_cpu_ids || !cpu_online(cpu))
>  		return VM_FAULT_SIGBUS;
>  	/*
>  	 * CPU Hotplug is not supported in VTL2 in OpenHCL, where this kernel driver exists.
> -- 
> 2.34.1