xen/arm: Don't use _end in is_xen_fixed_mfn()

virt_to_maddr() is using the hardware page-table walk instructions to
translate a virtual address to physical address. The function should
only be called on virtual address mapped.

_end points past the end of Xen binary and may not be mapped when the
binary size is page-aligned. This means virt_to_maddr() will not be able
to do the translation and therefore crash Xen.

Note there is also an off-by-one issue in this code, but the panic will
trump that.

Both issues can be fixed by using _end - 1 in the check.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Release-acked-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
(cherry picked from commit 8dba9a81e7c62b8a7dbe023fffecd2e16cc20486)

diff --git a/xen/include/asm-arm/mm.h b/xen/include/asm-arm/mm.h
index 940b74be332b1273a5f7eb5165b3fb7a975ab1d1..89fe10ff15f04725bd2ee86b26da4a73936e6a2f 100644 (file)
--- a/xen/include/asm-arm/mm.h
+++ b/xen/include/asm-arm/mm.h
@@ -152,7 +152,7 @@ extern vaddr_t xenheap_virt_start;
 
 #define is_xen_fixed_mfn(mfn)                                   \
     ((pfn_to_paddr(mfn) >= virt_to_maddr(&_start)) &&       \
-     (pfn_to_paddr(mfn) <= virt_to_maddr(&_end)))
+     (pfn_to_paddr(mfn) <= virt_to_maddr((vaddr_t)_end - 1)))
 
 #define page_get_owner(_p)    (_p)->v.inuse.domain
 #define page_set_owner(_p,_d) ((_p)->v.inuse.domain = (_d))