linux-kernel - [PATCH] mm/rmap: Fix potential pte

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Message-ID: <20210127093349.39081-1-linmiaohe@huawei.com>
Date:   Wed, 27 Jan 2021 04:33:49 -0500
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>
CC:     <mike.kravetz@...cle.com>, <shakeelb@...gle.com>,
        <hannes@...xchg.org>, <vbabka@...e.cz>, <walken@...gle.com>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <linmiaohe@...wei.com>
Subject: [PATCH] mm/rmap: Fix potential pte_unmap on an not mapped pte

For PMD-mapped page (usually THP), pvmw->pte is NULL. For PTE-mapped THP,
pvmw->pte is mapped. But for HugeTLB pages, pvmw->pte is not mapped and set
to the relevant page table entry. So in page_vma_mapped_walk_done(), we may
do pte_unmap() for HugeTLB pte which is not mapped. Fix this by checking
pvmw->page against PageHuge before trying to do pte_unmap().

Fixes: commit ("ace71a19cec5 mm: introduce page_vma_mapped_walk()")
Signed-off-by: Hongxiang Lou <louhongxiang@...wei.com>
Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
Cc: <stable@...r.kernel.org>
---
 include/linux/rmap.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 70085ca1a3fc..def5c62c93b3 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -213,7 +213,8 @@ struct page_vma_mapped_walk {
 
 static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
 {
-	if (pvmw->pte)
+	/* HugeTLB pte is set to the relevant page table entry without pte_mapped. */
+	if (pvmw->pte && !PageHuge(pvmw->page))
 		pte_unmap(pvmw->pte);
 	if (pvmw->ptl)
 		spin_unlock(pvmw->ptl);
-- 
2.19.1