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

[Roger Pau Monne <roger.pau@citrix.com>]

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@citrix.com>
---
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