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Date: Tue, 1 Nov 2022 18:31:00 -0700
From: Mike Kravetz <mike.kravetz@...cle.com>
To: linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc: Naoya Horiguchi <naoya.horiguchi@...ux.dev>,
David Hildenbrand <david@...hat.com>,
Axel Rasmussen <axelrasmussen@...gle.com>,
Mina Almasry <almasrymina@...gle.com>,
Peter Xu <peterx@...hat.com>,
Nadav Amit <nadav.amit@...il.com>,
Rik van Riel <riel@...riel.com>,
Vlastimil Babka <vbabka@...e.cz>,
Matthew Wilcox <willy@...radead.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Mike Kravetz <mike.kravetz@...cle.com>,
Wei Chen <harperchen1110@...il.com>, stable@...r.kernel.org
Subject: [PATCH v7] hugetlb: don't delete vma_lock in hugetlb MADV_DONTNEED processing
madvise(MADV_DONTNEED) ends up calling zap_page_range() to clear page
tables associated with the address range. For hugetlb vmas,
zap_page_range will call __unmap_hugepage_range_final. However,
__unmap_hugepage_range_final assumes the passed vma is about to be removed
and deletes the vma_lock to prevent pmd sharing as the vma is on the way
out. In the case of madvise(MADV_DONTNEED) the vma remains, but the
missing vma_lock prevents pmd sharing and could potentially lead to issues
with truncation/fault races.
This issue was originally reported here [1] as a BUG triggered in
page_try_dup_anon_rmap. Prior to the introduction of the hugetlb
vma_lock, __unmap_hugepage_range_final cleared the VM_MAYSHARE flag to
prevent pmd sharing. Subsequent faults on this vma were confused as
VM_MAYSHARE indicates a sharable vma, but was not set so page_mapping was
not set in new pages added to the page table. This resulted in pages that
appeared anonymous in a VM_SHARED vma and triggered the BUG.
Address issue by:
- Add a new zap flag ZAP_FLAG_UNMAP to indicate an unmap call from
unmap_vmas(). This is used to indicate the 'final' unmapping of a vma.
When called via MADV_DONTNEED, this flag is not set and the vm_lock is
not deleted.
- mmu notification is removed from __unmap_hugepage_range to avoid
duplication, and notification is added to the other calling routine
(unmap_hugepage_range).
- notification calls are updated in zap_page range to take into account
the possibility of multiple vmas.
[1] https://lore.kernel.org/lkml/CAO4mrfdLMXsao9RF4fUE8-Wfde8xmjsKrTNMNC9wjUb6JudD0g@mail.gmail.com/
Fixes: 90e7e7f5ef3f ("mm: enable MADV_DONTNEED for hugetlb mappings")
Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
Reported-by: Wei Chen <harperchen1110@...il.com>
Cc: <stable@...r.kernel.org>
---
include/linux/mm.h | 3 +++
mm/hugetlb.c | 45 +++++++++++++++++++++++++++------------------
mm/memory.c | 21 +++++++++++++++------
3 files changed, 45 insertions(+), 24 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 8bbcccbc5565..b19d65c36d14 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3475,4 +3475,7 @@ madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
*/
#define ZAP_FLAG_DROP_MARKER ((__force zap_flags_t) BIT(0))
+/* Set in unmap_vmas() to indicate an unmap call. Only used by hugetlb */
+#define ZAP_FLAG_UNMAP ((__force zap_flags_t) BIT(1))
+
#endif /* _LINUX_MM_H */
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 546df97c31e4..4699889f11e9 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5064,7 +5064,6 @@ static void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct
struct page *page;
struct hstate *h = hstate_vma(vma);
unsigned long sz = huge_page_size(h);
- struct mmu_notifier_range range;
unsigned long last_addr_mask;
bool force_flush = false;
@@ -5079,13 +5078,6 @@ static void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct
tlb_change_page_size(tlb, sz);
tlb_start_vma(tlb, vma);
- /*
- * If sharing possible, alert mmu notifiers of worst case.
- */
- mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma, mm, start,
- end);
- adjust_range_if_pmd_sharing_possible(vma, &range.start, &range.end);
- mmu_notifier_invalidate_range_start(&range);
last_addr_mask = hugetlb_mask_last_page(h);
address = start;
for (; address < end; address += sz) {
@@ -5174,7 +5166,6 @@ static void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct
if (ref_page)
break;
}
- mmu_notifier_invalidate_range_end(&range);
tlb_end_vma(tlb, vma);
/*
@@ -5199,32 +5190,50 @@ void __unmap_hugepage_range_final(struct mmu_gather *tlb,
unsigned long end, struct page *ref_page,
zap_flags_t zap_flags)
{
+ bool final = zap_flags & ZAP_FLAG_UNMAP;
+
hugetlb_vma_lock_write(vma);
i_mmap_lock_write(vma->vm_file->f_mapping);
__unmap_hugepage_range(tlb, vma, start, end, ref_page, zap_flags);
/*
- * Unlock and free the vma lock before releasing i_mmap_rwsem. When
- * the vma_lock is freed, this makes the vma ineligible for pmd
- * sharing. And, i_mmap_rwsem is required to set up pmd sharing.
- * This is important as page tables for this unmapped range will
- * be asynchrously deleted. If the page tables are shared, there
- * will be issues when accessed by someone else.
+ * When called via zap_page_range (MADV_DONTNEED), this is not the
+ * final unmap of the vma, and we do not want to delete the vma_lock.
*/
- __hugetlb_vma_unlock_write_free(vma);
-
- i_mmap_unlock_write(vma->vm_file->f_mapping);
+ if (final) {
+ /*
+ * Unlock and free the vma lock before releasing i_mmap_rwsem.
+ * When the vma_lock is freed, this makes the vma ineligible
+ * for pmd sharing. And, i_mmap_rwsem is required to set up
+ * pmd sharing. This is important as page tables for this
+ * unmapped range will be asynchrously deleted. If the page
+ * tables are shared, there will be issues when accessed by
+ * someone else.
+ */
+ __hugetlb_vma_unlock_write_free(vma);
+ i_mmap_unlock_write(vma->vm_file->f_mapping);
+ } else {
+ i_mmap_unlock_write(vma->vm_file->f_mapping);
+ hugetlb_vma_unlock_write(vma);
+ }
}
void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
unsigned long end, struct page *ref_page,
zap_flags_t zap_flags)
{
+ struct mmu_notifier_range range;
struct mmu_gather tlb;
+ mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma, vma->vm_mm,
+ start, end);
+ adjust_range_if_pmd_sharing_possible(vma, &range.start, &range.end);
tlb_gather_mmu(&tlb, vma->vm_mm);
+
__unmap_hugepage_range(&tlb, vma, start, end, ref_page, zap_flags);
+
+ mmu_notifier_invalidate_range_end(&range);
tlb_finish_mmu(&tlb);
}
diff --git a/mm/memory.c b/mm/memory.c
index f88c351aecd4..474c43156ecf 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1720,7 +1720,7 @@ void unmap_vmas(struct mmu_gather *tlb, struct maple_tree *mt,
{
struct mmu_notifier_range range;
struct zap_details details = {
- .zap_flags = ZAP_FLAG_DROP_MARKER,
+ .zap_flags = ZAP_FLAG_DROP_MARKER | ZAP_FLAG_UNMAP,
/* Careful - we need to zap private pages too! */
.even_cows = true,
};
@@ -1753,15 +1753,24 @@ void zap_page_range(struct vm_area_struct *vma, unsigned long start,
MA_STATE(mas, mt, vma->vm_end, vma->vm_end);
lru_add_drain();
- mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
- start, start + size);
tlb_gather_mmu(&tlb, vma->vm_mm);
update_hiwater_rss(vma->vm_mm);
- mmu_notifier_invalidate_range_start(&range);
do {
- unmap_single_vma(&tlb, vma, start, range.end, NULL);
+ mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma,
+ vma->vm_mm,
+ max(start, vma->vm_start),
+ min(end, vma->vm_end));
+ if (is_vm_hugetlb_page(vma))
+ adjust_range_if_pmd_sharing_possible(vma,
+ &range.start, &range.end);
+ mmu_notifier_invalidate_range_start(&range);
+ /*
+ * unmap 'start-end' not 'range.start-range.end' as range
+ * could have been expanded for pmd sharing.
+ */
+ unmap_single_vma(&tlb, vma, start, end, NULL);
+ mmu_notifier_invalidate_range_end(&range);
} while ((vma = mas_find(&mas, end - 1)) != NULL);
- mmu_notifier_invalidate_range_end(&range);
tlb_finish_mmu(&tlb);
}
--
2.37.3
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