5.4-stable patches

added patches:
	mm-khugepaged-fix-collapse_pte_mapped_thp-to-allow-anon_vma.patch

diff --git a/queue-5.4/mm-khugepaged-fix-collapse_pte_mapped_thp-to-allow-anon_vma.patch b/queue-5.4/mm-khugepaged-fix-collapse_pte_mapped_thp-to-allow-anon_vma.patch
new file mode 100644 (file)
index 0000000..5498a68
--- /dev/null
+++ b/queue-5.4/mm-khugepaged-fix-collapse_pte_mapped_thp-to-allow-anon_vma.patch
@@ -0,0 +1,86 @@
+From ab0c3f1251b4670978fde0bd54161795a139b060 Mon Sep 17 00:00:00 2001
+From: Hugh Dickins <hughd@google.com>
+Date: Thu, 22 Dec 2022 12:41:50 -0800
+Subject: mm/khugepaged: fix collapse_pte_mapped_thp() to allow anon_vma
+
+From: Hugh Dickins <hughd@google.com>
+
+commit ab0c3f1251b4670978fde0bd54161795a139b060 upstream.
+
+uprobe_write_opcode() uses collapse_pte_mapped_thp() to restore huge pmd,
+when removing a breakpoint from hugepage text: vma->anon_vma is always set
+in that case, so undo the prohibition.  And MADV_COLLAPSE ought to be able
+to collapse some page tables in a vma which happens to have anon_vma set
+from CoWing elsewhere.
+
+Is anon_vma lock required?  Almost not: if any page other than expected
+subpage of the non-anon huge page is found in the page table, collapse is
+aborted without making any change.  However, it is possible that an anon
+page was CoWed from this extent in another mm or vma, in which case a
+concurrent lookup might look here: so keep it away while clearing pmd (but
+perhaps we shall go back to using pmd_lock() there in future).
+
+Note that collapse_pte_mapped_thp() is exceptional in freeing a page table
+without having cleared its ptes: I'm uneasy about that, and had thought
+pte_clear()ing appropriate; but exclusive i_mmap lock does fix the
+problem, and we would have to move the mmu_notification if clearing those
+ptes.
+
+What this fixes is not a dangerous instability.  But I suggest Cc stable
+because uprobes "healing" has regressed in that way, so this should follow
+8d3c106e19e8 into those stable releases where it was backported (and may
+want adjustment there - I'll supply backports as needed).
+
+Link: https://lkml.kernel.org/r/b740c9fb-edba-92ba-59fb-7a5592e5dfc@google.com
+Fixes: 8d3c106e19e8 ("mm/khugepaged: take the right locks for page table retraction")
+Signed-off-by: Hugh Dickins <hughd@google.com>
+Acked-by: David Hildenbrand <david@redhat.com>
+Cc: Jann Horn <jannh@google.com>
+Cc: Yang Shi <shy828301@gmail.com>
+Cc: Zach O'Keefe <zokeefe@google.com>
+Cc: Song Liu <songliubraving@fb.com>
+Cc: <stable@vger.kernel.org>    [5.4+]
+Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ mm/khugepaged.c |   14 ++++++--------
+ 1 file changed, 6 insertions(+), 8 deletions(-)
+
+--- a/mm/khugepaged.c
++++ b/mm/khugepaged.c
+@@ -1328,14 +1328,6 @@ void collapse_pte_mapped_thp(struct mm_s
+       if (!hugepage_vma_check(vma, vma->vm_flags | VM_HUGEPAGE))
+               return;
+ 
+-      /*
+-       * Symmetry with retract_page_tables(): Exclude MAP_PRIVATE mappings
+-       * that got written to. Without this, we'd have to also lock the
+-       * anon_vma if one exists.
+-       */
+-      if (vma->anon_vma)
+-              return;
+-
+       hpage = find_lock_page(vma->vm_file->f_mapping,
+                              linear_page_index(vma, haddr));
+       if (!hpage)
+@@ -1407,6 +1399,10 @@ void collapse_pte_mapped_thp(struct mm_s
+       }
+ 
+       /* step 4: collapse pmd */
++      /* we make no change to anon, but protect concurrent anon page lookup */
++      if (vma->anon_vma)
++              anon_vma_lock_write(vma->anon_vma);
++
+       mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm, haddr,
+                               haddr + HPAGE_PMD_SIZE);
+       mmu_notifier_invalidate_range_start(&range);
+@@ -1416,6 +1412,8 @@ void collapse_pte_mapped_thp(struct mm_s
+       mmu_notifier_invalidate_range_end(&range);
+       pte_free(mm, pmd_pgtable(_pmd));
+ 
++      if (vma->anon_vma)
++              anon_vma_unlock_write(vma->anon_vma);
+       i_mmap_unlock_write(vma->vm_file->f_mapping);
+ 
+ drop_hpage:

diff --git a/queue-5.4/series b/queue-5.4/series
index 0a5f203cd4d35f837f29ee46100766b50cfee0b3..5dc059bd1b7a8b7858ce69241a8cd335ecf4f2d4 100644 (file)
--- a/queue-5.4/series
+++ b/queue-5.4/series
@@ -48,3 +48,4 @@ drm-i915-re-disable-rc6p-on-sandy-bridge.patch
 drm-amd-display-fix-set-scaling-doesn-s-work.patch
 drm-amd-display-fix-color_space_ycbcr2020_type-matrix.patch
 x86-fpu-use-_alignof-to-avoid-undefined-behavior-in-type_align.patch
+mm-khugepaged-fix-collapse_pte_mapped_thp-to-allow-anon_vma.patch