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mm/rmap: use huge_ptep_get() in try_to_unmap_one()

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Patch series "Fix incorrect access of hugetlb pte entries", v3.

There are various places which use ptep_get() to get the pte entry
corresponding to a hugetlb folio.  Some arches (like s390) have special
handling to compute the pteval, so they provide huge_ptep_get().  Use this
helper consistently.

Additionally, some code paths may provide huge_ptep_get with an unaligned
address.  This is a problem on arm64 (I checked other arches and it looks
fine for them), which is fixed in patch 1.  The fix is made to be
backport-friendly: the cleaner fix would be to perhaps pass the hstate to
huge_ptep_get() - that is wider churn and we can do that later.


This patch (of 5):

try_to_unmap_one() handles hugetlb folios when memory failure needs to
replace a poisoned hugetlb mapping with a hwpoison entry.  In that case
page_vma_mapped_walk() returns the pte pointer to the hugetlb folio in
pvmw.pte, but the code reads it with ptep_get().

On arches which provide their own huge_ptep_get() to dereference a huge
pte pointer, accessing via ptep_get() would cause pte_pfn(), pte_present()
etc to misbehave.

It is not clear whether this has a trivially visible effect to userspace.

Just use huge_ptep_get() for dereferencing a huge pte pointer.

Link: https://lore.kernel.org/20260703114202.365553-1-dev.jain@arm.com
Link: https://lore.kernel.org/20260703114202.365553-3-dev.jain@arm.com
Fixes: c7ab0d2fdc ("mm: convert try_to_unmap_one() to use page_vma_mapped_walk()")
Signed-off-by: Dev Jain <dev.jain@arm.com>
Reported-by: David Hildenbrand <david@kernel.org>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Gregory Price <gourry@gourry.net>
Cc: Harry Yoo <harry@kernel.org>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Jann Horn <jannh@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Jun'ichi "Nick" Nomura <j-nomura@ce.jp.nec.com>
Cc: Kiryl Shutsemau <kas@kernel.org>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Will Deacon <will@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Dev Jain
2026-07-03 11:41:55 +00:00
committed by Andrew Morton
parent 3a01af8281
commit f5407e9b69
2 changed files with 12 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/hugetlb.h
View File

@@ -1270,6 +1270,8 @@ static inline void hugetlb_count_sub(long l, struct mm_struct *mm)
{
}
pte_t huge_ptep_get(struct mm_struct *mm, unsigned long addr, pte_t *ptep);
static inline pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,
unsigned long addr, pte_t *ptep)
{

16
mm/rmap.c
View File

@@ -2095,14 +2095,19 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
/* Unexpected PMD-mapped THP? */
VM_BUG_ON_FOLIO(!pvmw.pte, folio);
/*
* Handle PFN swap PTEs, such as device-exclusive ones, that
* actually map pages.
*/
pteval = ptep_get(pvmw.pte);
address = pvmw.address;
if (folio_test_hugetlb(folio)) {
pteval = huge_ptep_get(mm, address, pvmw.pte);
} else {
pteval = ptep_get(pvmw.pte);
}
if (likely(pte_present(pteval))) {
pfn = pte_pfn(pteval);
} else {
/*
* Handle PFN swap PTEs, such as device-exclusive ones,
* that actually map pages.
*/
const softleaf_t entry = softleaf_from_pte(pteval);
pfn = softleaf_to_pfn(entry);
@@ -2110,7 +2115,6 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
}
subpage = folio_page(folio, pfn - folio_pfn(folio));
address = pvmw.address;
anon_exclusive = folio_test_anon(folio) &&
PageAnonExclusive(subpage);