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.gr...@arm.com>
Release-acked-by: Juergen Gross <jgr...@suse.com>
---
Cc: Andrew Cooper <andrew.coop...@citrix.com>
Cc: George Dunlap <george.dun...@eu.citrix.com>
Cc: Ian Jackson <ian.jack...@eu.citrix.com>
Cc: Jan Beulich <jbeul...@suse.com>
Cc: Julien Grall <jul...@xen.org>
Cc: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
Cc: Stefano Stabellini <sstabell...@kernel.org>
Cc: Tim Deegan <t...@xen.org>
Cc: Wei Liu <w...@xen.org>
x86 seems to be affected by the off-by-one issue. Jan, Andrew?
This could be reached by a domain via XEN_SYSCTL_page_offline_op.
However, the operation is not security supported (see XSA-77). So we are
fine here.
Changes in v2:
- Cast _end to vaddr_t to prevent UB.
- Add Juergen's released-acked-by
---
xen/include/asm-arm/mm.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/xen/include/asm-arm/mm.h b/xen/include/asm-arm/mm.h
index 262d92f18d..333efd3a60 100644
--- a/xen/include/asm-arm/mm.h
+++ b/xen/include/asm-arm/mm.h
@@ -153,7 +153,7 @@ extern unsigned long xenheap_base_pdx;
#define is_xen_fixed_mfn(mfn) \
((mfn_to_maddr(mfn) >= virt_to_maddr(&_start)) && \
- (mfn_to_maddr(mfn) <= virt_to_maddr(&_end)))
+ (mfn_to_maddr(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))
--
2.11.0
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