4.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Krzysztof Mazur <[email protected]>

commit 68accac392d859d24adcf1be3a90e41f978bd54c upstream.

The commit f5f3497cad8c extended the low identity mapping. However, if
the kernel uses more than 2 GB (VMSPLIT_2G_OPT or VMSPLIT_1G memory
split), the normal memory mapping is overwritten by the low identity
mapping causing a crash. To avoid overwritting, limit the low identity
map to cover only memory before kernel range (PAGE_OFFSET).

Fixes: f5f3497cad8c "x86/setup: Extend low identity map to cover whole kernel 
range
Signed-off-by: Krzysztof Mazur <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Laszlo Ersek <[email protected]>
Cc: Matt Fleming <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Link: 
http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

---
 arch/x86/kernel/setup.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1205,7 +1205,7 @@ void __init setup_arch(char **cmdline_p)
         */
        clone_pgd_range(initial_page_table,
                        swapper_pg_dir     + KERNEL_PGD_BOUNDARY,
-                       KERNEL_PGD_PTRS);
+                       min(KERNEL_PGD_PTRS, KERNEL_PGD_BOUNDARY));
 #endif
 
        tboot_probe();


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