Re: [PATCH v4 1/1] x86/ioremap: Fix page aligned size calculation in __ioremap_caller()

[Wei Liu]

On Tue, Nov 22, 2022 at 09:40:42AM -0800, Michael Kelley wrote:
> Current code re-calculates the size after aligning the starting and
> ending physical addresses on a page boundary. But the re-calculation
> also embeds the masking of high order bits that exceed the size of
> the physical address space (via PHYSICAL_PAGE_MASK). If the masking
> removes any high order bits, the size calculation results in a huge
> value that is likely to immediately fail.
> 
> Fix this by re-calculating the page-aligned size first. Then mask any
> high order bits using PHYSICAL_PAGE_MASK.
> 
> Fixes: ffa71f33a820 ("x86, ioremap: Fix incorrect physical address handling in PAE mode")
> Acked-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> Signed-off-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>

Reviewed-by: Wei Liu <wei.liu@xxxxxxxxxx>

> ---
> 
> This patch was previously Patch 1 of a larger series[1].  Breaking
> it out separately per discussion with Dave Hansen and Boris Petkov.
> 
> [1] https://lore.kernel.org/linux-hyperv/1668624097-14884-1-git-send-email-mikelley@xxxxxxxxxxxxx/
> 
>  arch/x86/mm/ioremap.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
> index 78c5bc6..6453fba 100644
> --- a/arch/x86/mm/ioremap.c
> +++ b/arch/x86/mm/ioremap.c
> @@ -217,9 +217,15 @@ static void __ioremap_check_mem(resource_size_t addr, unsigned long size,
>  	 * Mappings have to be page-aligned
>  	 */
>  	offset = phys_addr & ~PAGE_MASK;
> -	phys_addr &= PHYSICAL_PAGE_MASK;
> +	phys_addr &= PAGE_MASK;
>  	size = PAGE_ALIGN(last_addr+1) - phys_addr;
>  
> +	/*
> +	 * Mask out any bits not part of the actual physical
> +	 * address, like memory encryption bits.
> +	 */
> +	phys_addr &= PHYSICAL_PAGE_MASK;
> +
>  	retval = memtype_reserve(phys_addr, (u64)phys_addr + size,
>  						pcm, &new_pcm);
>  	if (retval) {
> -- 
> 1.8.3.1
>