Re: [PATCH 1/2] domain: fix misaligned unmap address in unmap_guest_area()

[Henry Wang <Henry.Wang@xxxxxxx>]

Hi Roger,

> On Oct 6, 2023, at 17:13, Roger Pau Monne <roger.pau@xxxxxxxxxx> wrote:
> 
> unmap_domain_page_global() expects the provided address to be page aligned, or
> else some of the called functions will trigger assertions, like
> modify_xen_mappings() on x86 or destroy_xen_mappings() on Arm.
> 
> The following assert has been reported by osstest arm 32bit tests:
> 
> (XEN) Assertion 'IS_ALIGNED(s, PAGE_SIZE)' failed at arch/arm/mm.c:1243
> (XEN) ----[ Xen-4.18-rc  arm32  debug=y  Not tainted ]----
> (XEN) CPU:    0
> (XEN) PC:     00271a38 destroy_xen_mappings+0x50/0x5c
> [...]
> (XEN) Xen call trace:
> (XEN)    [<00271a38>] destroy_xen_mappings+0x50/0x5c (PC)
> (XEN)    [<00235aa8>] vunmap+0x30/0x1a0 (LR)
> (XEN)    [<0026ad88>] unmap_domain_page_global+0x10/0x20
> (XEN)    [<00208e38>] unmap_guest_area+0x90/0xec
> (XEN)    [<00208f98>] domain_kill+0x104/0x180
> (XEN)    [<00239e3c>] do_domctl+0x8ac/0x14fc
> (XEN)    [<0027ae34>] do_trap_guest_sync+0x570/0x66c
> (XEN)    [<002019f0>] arch/arm/arm32/entry.o#return_from_trap+0/0x4
> 
> Fixes: eadc288cbb0d ('domain: map/unmap GADDR based shared guest areas')
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Release-acked-by: Henry Wang <Henry.Wang@xxxxxxx>

Kind regards,
Henry

> ---
> unmap_domain_page_global() and vunmap() should likely have the same alignment
> asserts, as not all paths lead to detecting the misalignment of the provided
> linear address.  Will do a separate patch.
> ---
> xen/common/domain.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/xen/common/domain.c b/xen/common/domain.c
> index b8281d7cff9d..2dcc64e659cc 100644
> --- a/xen/common/domain.c
> +++ b/xen/common/domain.c
> @@ -1634,7 +1634,7 @@ void unmap_guest_area(struct vcpu *v, struct guest_area 
> *area)
> 
>     if ( pg )
>     {
> -        unmap_domain_page_global(map);
> +        unmap_domain_page_global((void *)((unsigned long)map & PAGE_MASK));
>         put_page_and_type(pg);
>     }
> }
> -- 
> 2.42.0
>