+ mm-khugepaged-fix-invalid-page-access-in-release_pte_pages.patch added to mm-unstable branch

+ mm-khugepaged-fix-invalid-page-access-in-release_pte_pages.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/khugepaged: fix invalid page access in release_pte_pages()
has been added to the -mm mm-unstable branch.  Its filename is
     mm-khugepaged-fix-invalid-page-access-in-release_pte_pages.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-khugepaged-fix-invalid-page-access-in-release_pte_pages.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: "Vishal Moola (Oracle)" <vishal.moola@gmail.com>
Subject: mm/khugepaged: fix invalid page access in release_pte_pages()
Date: Mon, 13 Feb 2023 13:43:24 -0800

release_pte_pages() converts from a pfn to a folio by using pfn_folio(). 
If the pte is not mapped, pfn_folio() will result in undefined behavior
which ends up causing a kernel panic[1].

Only call pfn_folio() once we have validated that the pte is both valid
and mapped to fix the issue.

[1] https://lore.kernel.org/linux-mm/ff300770-afe9-908d-23ed-d23e0796e899@samsung.com/

Link: https://lkml.kernel.org/r/20230213214324.34215-1-vishal.moola@gmail.com
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Fixes: 9bdfeea46f49 ("mm/khugepaged: convert release_pte_pages() to use folios")
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Debugged-by: Alexandre Ghiti <alex@ghiti.fr>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---


--- a/mm/khugepaged.c~mm-khugepaged-fix-invalid-page-access-in-release_pte_pages
+++ a/mm/khugepaged.c
@@ -511,11 +511,17 @@ static void release_pte_pages(pte_t *pte
 
 	while (--_pte >= pte) {
 		pte_t pteval = *_pte;
+		unsigned long pfn;
 
-		folio = pfn_folio(pte_pfn(pteval));
-		if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)) &&
-				!folio_test_large(folio))
-			release_pte_folio(folio);
+		if (pte_none(pteval))
+			continue;
+		pfn = pte_pfn(pteval);
+		if (is_zero_pfn(pfn))
+			continue;
+		folio = pfn_folio(pfn);
+		if (folio_test_large(folio))
+			continue;
+		release_pte_folio(folio);
 	}
 
 	list_for_each_entry_safe(folio, tmp, compound_pagelist, lru) {
_

Patches currently in -mm which might be from vishal.moola@gmail.com are

mm-khugepaged-fix-invalid-page-access-in-release_pte_pages.patch
mm-add-folio_estimated_sharers.patch
mm-mempolicy-convert-queue_pages_pmd-to-queue_folios_pmd.patch
mm-mempolicy-convert-queue_pages_pte_range-to-queue_folios_pte_range.patch
mm-mempolicy-convert-queue_pages_hugetlb-to-queue_folios_hugetlb.patch
mm-mempolicy-convert-queue_pages_required-to-queue_folio_required.patch
mm-mempolicy-convert-migrate_page_add-to-migrate_folio_add.patch
mm-add-folio_get_nontail_page.patch
mm-migrate-add-folio_movable_ops.patch
mm-migrate-convert-isolate_movable_page-to-use-folios.patch
mm-migrate-convert-putback_movable_pages-to-use-folios.patch