linux-kernel - [PATCH 3.4 028/172] mm/hugetlb: add migration/hwpoisoned entry check in hugetlb_change

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Date:	Tue, 16 Jun 2015 16:34:42 +0800
From:	lizf@...nel.org
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Hugh Dickins <hughd@...gle.com>,
	James Hogan <james.hogan@...tec.com>,
	David Rientjes <rientjes@...gle.com>,
	Mel Gorman <mel@....ul.ie>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>, Rik van Riel <riel@...hat.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Luiz Capitulino <lcapitulino@...hat.com>,
	Nishanth Aravamudan <nacc@...ux.vnet.ibm.com>,
	Lee Schermerhorn <lee.schermerhorn@...com>,
	Steve Capper <steve.capper@...aro.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Zefan Li <lizefan@...wei.com>
Subject: [PATCH 3.4 028/172] mm/hugetlb: add migration/hwpoisoned entry check in hugetlb_change_protection

From: Naoya Horiguchi <n-horiguchi@...jp.nec.com>

3.4.108-rc1 review patch.  If anyone has any objections, please let me know.

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


commit a8bda28d87c38c6aa93de28ba5d30cc18e865a11 upstream.

There is a race condition between hugepage migration and
change_protection(), where hugetlb_change_protection() doesn't care about
migration entries and wrongly overwrites them.  That causes unexpected
results like kernel crash.  HWPoison entries also can cause the same
problem.

This patch adds is_hugetlb_entry_(migration|hwpoisoned) check in this
function to do proper actions.

Fixes: 290408d4a2 ("hugetlb: hugepage migration core")
Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: James Hogan <james.hogan@...tec.com>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Mel Gorman <mel@....ul.ie>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: Michal Hocko <mhocko@...e.cz>
Cc: Rik van Riel <riel@...hat.com>
Cc: Andrea Arcangeli <aarcange@...hat.com>
Cc: Luiz Capitulino <lcapitulino@...hat.com>
Cc: Nishanth Aravamudan <nacc@...ux.vnet.ibm.com>
Cc: Lee Schermerhorn <lee.schermerhorn@...com>
Cc: Steve Capper <steve.capper@...aro.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
[lizf: Backported to 3.4:
 - remove locking of ptl
 - remove counting of pages]
Signed-off-by: Zefan Li <lizefan@...wei.com>
---
 mm/hugetlb.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index d02fbbc..5f12dba 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3052,7 +3052,22 @@ void hugetlb_change_protection(struct vm_area_struct *vma,
 			continue;
 		if (huge_pmd_unshare(mm, &address, ptep))
 			continue;
-		if (!huge_pte_none(huge_ptep_get(ptep))) {
+		pte = huge_ptep_get(ptep);
+		if (unlikely(is_hugetlb_entry_hwpoisoned(pte)))
+			continue;
+		if (unlikely(is_hugetlb_entry_migration(pte))) {
+			swp_entry_t entry = pte_to_swp_entry(pte);
+
+			if (is_write_migration_entry(entry)) {
+				pte_t newpte;
+
+				make_migration_entry_read(&entry);
+				newpte = swp_entry_to_pte(entry);
+				set_huge_pte_at(mm, address, ptep, newpte);
+			}
+			continue;
+		}
+		if (!huge_pte_none(pte)) {
 			pte = huge_ptep_get_and_clear(mm, address, ptep);
 			pte = pte_mkhuge(pte_modify(pte, newprot));
 			set_huge_pte_at(mm, address, ptep, pte);
-- 
1.9.1

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