Patch "arm64: mm: ensure that the zero page is visible to the page table walker" has been added to the 4.1-stable tree

Patch "arm64: mm: ensure that the zero page is visible to the page table walker" has been added to the 4.1-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    arm64: mm: ensure that the zero page is visible to the page table walker

to the 4.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     arm64-mm-ensure-that-the-zero-page-is-visible-to-the-page-table-walker.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 32d6397805d00573ce1fa55f408ce2bca15b0ad3 Mon Sep 17 00:00:00 2001
From: Will Deacon <will.deacon@arm.com>
Date: Thu, 10 Dec 2015 16:05:36 +0000
Subject: arm64: mm: ensure that the zero page is visible to the page table walker

From: Will Deacon <will.deacon@arm.com>

commit 32d6397805d00573ce1fa55f408ce2bca15b0ad3 upstream.

In paging_init, we allocate the zero page, memset it to zero and then
point TTBR0 to it in order to avoid speculative fetches through the
identity mapping.

In order to guarantee that the freshly zeroed page is indeed visible to
the page table walker, we need to execute a dsb instruction prior to
writing the TTBR.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/arm64/mm/mmu.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -450,6 +450,9 @@ void __init paging_init(void)
 
 	empty_zero_page = virt_to_page(zero_page);
 
+	/* Ensure the zero page is visible to the page table walker */
+	dsb(ishst);
+
 	/*
 	 * TTBR0 is only used for the identity mapping at this stage. Make it
 	 * point to zero page to avoid speculatively fetching new entries.


Patches currently in stable-queue which might be from will.deacon@arm.com are

queue-4.1/arm64-kernel-pause-unpause-function-graph-tracer-in-cpu_suspend.patch
queue-4.1/arm64-mm-ensure-that-the-zero-page-is-visible-to-the-page-table-walker.patch
queue-4.1/arm64-fix-building-without-config_uid16.patch
queue-4.1/arm64-clear-out-any-singlestep-state-on-a-ptrace-detach-operation.patch
queue-4.1/recordmcount-arm64-replace-the-ignored-mcount-call-into-nop.patch