[Xen-changelog] [xen stable-4.12] xen/arm: Don't use _end in is_xen_fixed_mfn()

[patchbot@xxxxxxx]

commit 5f1c9e437b588563b687b1bf8c9ca3b16af5ec94
Author:     Julien Grall <julien.grall@xxxxxxx>
AuthorDate: Wed Oct 16 11:53:03 2019 +0100
Commit:     Stefano Stabellini <sstabellini@xxxxxxxxxx>
CommitDate: Tue Oct 29 10:58:47 2019 -0700

    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@xxxxxxx>
    Release-acked-by: Juergen Gross <jgross@xxxxxxxx>
    Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
    (cherry picked from commit 8dba9a81e7c62b8a7dbe023fffecd2e16cc20486)
---
 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 eafa26f56e..7ded2066e5 100644
--- 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))
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.12

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