Re: [PATCH v2 1/4] irqchip/gic-v3-its: Zero shared pages after conversion

[Catalin Marinas <catalin.marinas@arm.com>]

On Thu, Aug 20, 2026 at 04:00:30PM +0100, Steven Price wrote:
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index 6f5811aae59c..a055837832bc 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -213,16 +213,18 @@ static gfp_t gfp_flags_quirk;
>  static struct page *its_alloc_pages_node(int node, gfp_t gfp,
>  					 unsigned int order)
>  {
> +	bool want_zero = gfp & __GFP_ZERO;
>  	struct page *page;
>  	int ret = 0;
>  
> -	page = alloc_pages_node(node, gfp | gfp_flags_quirk, order);
> +	page = alloc_pages_node(node, (gfp & ~__GFP_ZERO) | gfp_flags_quirk,
> +				order);

I don't think pKVM does any scrubbing on set_memory_decrypted(), so it
potentially exposes confidential guest data before it reaches
clear_pages() below.

>  
>  	if (!page)
>  		return NULL;
>  
>  	ret = set_memory_decrypted((unsigned long)page_address(page),
> -				   1 << order);
> +				   BIT(order));
>  	/*
>  	 * If set_memory_decrypted() fails then we don't know what state the
>  	 * page is in, so we can't free it. Instead we leak it.
> @@ -231,6 +233,9 @@ static struct page *its_alloc_pages_node(int node, gfp_t gfp,
>  	if (ret)
>  		return NULL;
>  
> +	if (want_zero)
> +		clear_pages(page_address(page), BIT(order));
> +
>  	return page;
>  }
>  
> -- 
> 2.43.0

-- 
Catalin