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 <[email protected]> Release-acked-by: Juergen Gross <[email protected]> --- Cc: Andrew Cooper <[email protected]> Cc: George Dunlap <[email protected]> Cc: Ian Jackson <[email protected]> Cc: Jan Beulich <[email protected]> Cc: Julien Grall <[email protected]> Cc: Konrad Rzeszutek Wilk <[email protected]> Cc: Stefano Stabellini <[email protected]> Cc: Tim Deegan <[email protected]> Cc: Wei Liu <[email protected]> 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 _______________________________________________ Xen-devel mailing list [email protected] https://lists.xenproject.org/mailman/listinfo/xen-devel
