[added,to,the,3.12,stable,tree] arm64: Don't report clear pmds and puds as huge

Message ID 1438595559-22252-49-git-send-email-jslaby@suse.cz
State New
Headers show

Commit Message

Jiri Slaby Aug. 3, 2015, 9:52 a.m.
From: Christoffer Dall <christoffer.dall@linaro.org>

This patch has been added to the 3.12 stable tree. If you have any
objections, please let us know.

Patch

===============

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: Jiri Slaby <jslaby@suse.cz>
---
 arch/arm64/mm/hugetlbpage.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index 2de9d2e59d96..0eeb4f0930a0 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -40,13 +40,13 @@  int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep)
 
 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