linux-kernel - [PATCH 4.19 15/34] mm: page_vma_mapped_walk(): crossing page table boundary

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Message-Id: <20210709131652.947844814@linuxfoundation.org>
Date:   Fri,  9 Jul 2021 15:20:31 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hugh Dickins <hughd@...gle.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Alistair Popple <apopple@...dia.com>,
        Matthew Wilcox <willy@...radead.org>,
        Peter Xu <peterx@...hat.com>,
        Ralph Campbell <rcampbell@...dia.com>,
        Wang Yugui <wangyugui@...-tech.com>,
        Will Deacon <will@...nel.org>, Yang Shi <shy828301@...il.com>,
        Zi Yan <ziy@...dia.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 15/34] mm: page_vma_mapped_walk(): crossing page table boundary

From: Hugh Dickins <hughd@...gle.com>

[ Upstream commit 448282487483d6fa5b2eeeafaa0acc681e544a9c ]

page_vma_mapped_walk() cleanup: adjust the test for crossing page table
boundary - I believe pvmw->address is always page-aligned, but nothing
else here assumed that; and remember to reset pvmw->pte to NULL after
unmapping the page table, though I never saw any bug from that.

Link: https://lkml.kernel.org/r/799b3f9c-2a9e-dfef-5d89-26e9f76fd97@google.com
Signed-off-by: Hugh Dickins <hughd@...gle.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Alistair Popple <apopple@...dia.com>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: Peter Xu <peterx@...hat.com>
Cc: Ralph Campbell <rcampbell@...dia.com>
Cc: Wang Yugui <wangyugui@...-tech.com>
Cc: Will Deacon <will@...nel.org>
Cc: Yang Shi <shy828301@...il.com>
Cc: Zi Yan <ziy@...dia.com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 mm/page_vma_mapped.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index e32ed7912923..1fccadd0eb6d 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -240,16 +240,16 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
 			if (pvmw->address >= end)
 				return not_found(pvmw);
 			/* Did we cross page table boundary? */
-			if (pvmw->address % PMD_SIZE == 0) {
-				pte_unmap(pvmw->pte);
+			if ((pvmw->address & (PMD_SIZE - PAGE_SIZE)) == 0) {
 				if (pvmw->ptl) {
 					spin_unlock(pvmw->ptl);
 					pvmw->ptl = NULL;
 				}
+				pte_unmap(pvmw->pte);
+				pvmw->pte = NULL;
 				goto restart;
-			} else {
-				pvmw->pte++;
 			}
+			pvmw->pte++;
 		} while (pte_none(*pvmw->pte));
 
 		if (!pvmw->ptl) {
-- 
2.30.2