[PATCH 4.2 055/124] x86/setup: Fix low identity map for >= 2GB kernel range

[Greg Kroah-Hartman]

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

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

From: Krzysztof Mazur <krzysiek@xxxxxxxxxxxx>

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 <krzysiek@xxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Laszlo Ersek <lersek@xxxxxxxxxx>
Cc: Matt Fleming <matt.fleming@xxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/1446815916-22105-1-git-send-email-krzysiek@xxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 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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