Patch "arm64: Don't report clear pmds and puds as huge" has been added to the 4.1-stable tree

Patch "arm64: Don't report clear pmds and puds as huge" 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: Don't report clear pmds and puds as huge

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-don-t-report-clear-pmds-and-puds-as-huge.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 fd28f5d439fca77348c129d5b73043a56f8a0296 Mon Sep 17 00:00:00 2001
From: Christoffer Dall <christoffer.dall@linaro.org>
Date: Wed, 1 Jul 2015 14:08:31 +0200
Subject: arm64: Don't report clear pmds and puds as huge

From: Christoffer Dall <christoffer.dall@linaro.org>

commit fd28f5d439fca77348c129d5b73043a56f8a0296 upstream.

The current pmd_huge() and pud_huge() functions simply check if the table
bit is not set and reports the entries as huge in that case.  This is
counter-intuitive as a clear pmd/pud cannot also be a huge pmd/pud, and
it is inconsistent with at least arm and x86.

To prevent others from making the same mistake as me in looking at code
that calls these functions and to fix an issue with KVM on arm64 that
causes memory corruption due to incorrect page reference counting
resulting from this mistake, let's change the behavior.

Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Reviewed-by: Steve Capper <steve.capper@linaro.org>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Fixes: 084bd29810a5 ("ARM64: mm: HugeTLB support.")
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/arm64/mm/hugetlbpage.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -40,13 +40,13 @@ int huge_pmd_unshare(struct mm_struct *m
 
 int pmd_huge(pmd_t pmd)
 {
-	return !(pmd_val(pmd) & PMD_TABLE_BIT);
+	return pmd_val(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT);
 }
 
 int pud_huge(pud_t pud)
 {
 #ifndef __PAGETABLE_PMD_FOLDED
-	return !(pud_val(pud) & PUD_TABLE_BIT);
+	return pud_val(pud) && !(pud_val(pud) & PUD_TABLE_BIT);
 #else
 	return 0;
 #endif


Patches currently in stable-queue which might be from christoffer.dall@linaro.org are

queue-4.1/arm64-don-t-report-clear-pmds-and-puds-as-huge.patch