linux-kernel - [PATCH] mm: hugetlb: fix dissolve_free_huge

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Date:   Thu, 27 May 2021 16:12:25 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Linux-MM <linux-mm@...ck.org>, lkml <linux-kernel@...r.kernel.org>
Cc:     Muchun Song <songmuchun@...edance.com>,
        Michal Hocko <mhocko@...e.com>,
        Oscar Salvador <osalvador@...e.de>,
        David Hildenbrand <david@...hat.com>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>
Subject: [PATCH] mm: hugetlb: fix dissolve_free_huge_page use of tail/head page

The routine dissolve_free_huge_page can be passed the tail page of a
hugetlb page.  The tail page is incorrectly passed on to the routines
alloc_huge_page_vmemmap and add_hugetlb_page which expect a hugetlb
head page.

Operating on a tail page instead of head page could result in addressing
exceptions or vmemmap corruption.

Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
---
The code with this issue is only in mmotm (and next).  Specifically
mm: hugetlb: alloc the vmemmap pages associated with each HugeTLB page
Andrew, I assume you will fix in your tree.

 mm/hugetlb.c            | 4 ++--
 scripts/rust-version.sh | 0
 2 files changed, 2 insertions(+), 2 deletions(-)
 mode change 100644 => 100755 scripts/rust-version.sh

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 69a4b551c157..d2461c1f32dd 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1954,7 +1954,7 @@ int dissolve_free_huge_page(struct page *page)
 		 * Attempt to allocate vmemmmap here so that we can take
 		 * appropriate action on failure.
 		 */
-		rc = alloc_huge_page_vmemmap(h, page);
+		rc = alloc_huge_page_vmemmap(h, head);
 		if (!rc) {
 			/*
 			 * Move PageHWPoison flag from head page to the raw
@@ -1968,7 +1968,7 @@ int dissolve_free_huge_page(struct page *page)
 			update_and_free_page(h, head, false);
 		} else {
 			spin_lock_irq(&hugetlb_lock);
-			add_hugetlb_page(h, page, false);
+			add_hugetlb_page(h, head, false);
 			h->max_huge_pages++;
 			spin_unlock_irq(&hugetlb_lock);
 		}
diff --git a/scripts/rust-version.sh b/scripts/rust-version.sh
old mode 100644
new mode 100755
-- 
2.31.1