[3.16.y-ckt stable] Patch "x86/setup: Fix low identity map for >= 2GB kernel range" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    x86/setup: Fix low identity map for >= 2GB kernel range

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt21.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 7cb427ea093fa65db28a43c3be11f748cba3dbc6 Mon Sep 17 00:00:00 2001
From: Krzysztof Mazur <krzysiek at podlesie.net>
Date: Fri, 6 Nov 2015 14:18:36 +0100
Subject: x86/setup: Fix low identity map for >= 2GB kernel range

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 at podlesie.net>
Cc: Andy Lutomirski <luto at amacapital.net>
Cc: Borislav Petkov <bp at alien8.de>
Cc: Laszlo Ersek <lersek at redhat.com>
Cc: Matt Fleming <matt.fleming at intel.com>
Cc: Paolo Bonzini <pbonzini at redhat.com>
Link: http://lkml.kernel.org/r/1446815916-22105-1-git-send-email-krzysiek@podlesie.net
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 arch/x86/kernel/setup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 56788204d85e..b1077b8ee7af 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1184,7 +1184,7 @@ 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();