linux-kernel - [PATCH] mm: fix apply_to_existing_page

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Message-ID: <20250409094043.1629234-1-kirill.shutemov@linux.intel.com>
Date: Wed,  9 Apr 2025 12:40:43 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: David Hildenbrand <david@...hat.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Daniel Axtens <dja@...ens.net>
Subject: [PATCH] mm: fix apply_to_existing_page_range()

In the case of apply_to_existing_page_range(), apply_to_pte_range() is
reached with 'create' set to false. When !create, the loop over the PTE
page table is broken.

apply_to_pte_range() will only move to the next PTE entry if 'create' is
true or if the current entry is not pte_none().

This means that the user of apply_to_existing_page_range() will not have
'fn' called for any entries after the first pte_none() in the PTE page
table.

Fix the loop logic in apply_to_pte_range().

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Fixes: be1db4753ee6 ("mm/memory.c: add apply_to_existing_page_range() helper")
Cc: Daniel Axtens <dja@...ens.net>
---
 mm/memory.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index fb7b8dc75167..2094564f4dfb 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2907,11 +2907,11 @@ static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
 	if (fn) {
 		do {
 			if (create || !pte_none(ptep_get(pte))) {
-				err = fn(pte++, addr, data);
+				err = fn(pte, addr, data);
 				if (err)
 					break;
 			}
-		} while (addr += PAGE_SIZE, addr != end);
+		} while (pte++, addr += PAGE_SIZE, addr != end);
 	}
 	*mask |= PGTBL_PTE_MODIFIED;
 
-- 
2.47.2