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mm/hugetlb: fix uffd-wp during fork() 

Patch series "mm/hugetlb: More fixes around uffd-wp vs fork() / RO pins",
v2.


This patch (of 6):

There're a bunch of things that were wrong:

  - Reading uffd-wp bit from a swap entry should use pte_swp_uffd_wp()
    rather than huge_pte_uffd_wp().

  - When copying over a pte, we should drop uffd-wp bit when
    !EVENT_FORK (aka, when !userfaultfd_wp(dst_vma)).

  - When doing early CoW for private hugetlb (e.g. when the parent page was
    pinned), uffd-wp bit should be properly carried over if necessary.

No bug reported probably because most people do not even care about these
corner cases, but they are still bugs and can be exposed by the recent unit
tests introduced, so fix all of them in one shot.

Link: https://lkml.kernel.org/r/20230417195317.898696-1-peterx@redhat.com
Link: https://lkml.kernel.org/r/20230417195317.898696-2-peterx@redhat.com
Fixes: bc70fbf269 ("mm/hugetlb: handle uffd-wp during fork()")
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Mika Penttilä <mpenttil@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Peter Xu 2023-04-17 15:53:12 -04:00 committed by Andrew Morton
parent be41d814c6
commit 5a2f8d22ac
1 changed files with 15 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
mm/hugetlb.c
View File

@ -4953,11 +4953,15 @@ static bool is_hugetlb_entry_hwpoisoned(pte_t pte)
static void
hugetlb_install_folio(struct vm_area_struct *vma, pte_t *ptep, unsigned long addr,
struct folio *new_folio)
struct folio *new_folio, pte_t old)
{
pte_t newpte = make_huge_pte(vma, &new_folio->page, 1);
__folio_mark_uptodate(new_folio);
hugepage_add_new_anon_rmap(new_folio, vma, addr);
set_huge_pte_at(vma->vm_mm, addr, ptep, make_huge_pte(vma, &new_folio->page, 1));
if (userfaultfd_wp(vma) && huge_pte_uffd_wp(old))
newpte = huge_pte_mkuffd_wp(newpte);
set_huge_pte_at(vma->vm_mm, addr, ptep, newpte);
hugetlb_count_add(pages_per_huge_page(hstate_vma(vma)), vma->vm_mm);
folio_set_hugetlb_migratable(new_folio);
}
@ -5032,14 +5036,12 @@ again:
*/
;
} else if (unlikely(is_hugetlb_entry_hwpoisoned(entry))) {
bool uffd_wp = huge_pte_uffd_wp(entry);
if (!userfaultfd_wp(dst_vma) && uffd_wp)
if (!userfaultfd_wp(dst_vma))
entry = huge_pte_clear_uffd_wp(entry);
set_huge_pte_at(dst, addr, dst_pte, entry);
} else if (unlikely(is_hugetlb_entry_migration(entry))) {
swp_entry_t swp_entry = pte_to_swp_entry(entry);
bool uffd_wp = huge_pte_uffd_wp(entry);
bool uffd_wp = pte_swp_uffd_wp(entry);
if (!is_readable_migration_entry(swp_entry) && cow) {
/*
@ -5050,10 +5052,10 @@ again:
swp_offset(swp_entry));
entry = swp_entry_to_pte(swp_entry);
if (userfaultfd_wp(src_vma) && uffd_wp)
entry = huge_pte_mkuffd_wp(entry);
entry = pte_swp_mkuffd_wp(entry);
set_huge_pte_at(src, addr, src_pte, entry);
}
if (!userfaultfd_wp(dst_vma) && uffd_wp)
if (!userfaultfd_wp(dst_vma))
entry = huge_pte_clear_uffd_wp(entry);
set_huge_pte_at(dst, addr, dst_pte, entry);
} else if (unlikely(is_pte_marker(entry))) {
@ -5118,7 +5120,8 @@ again:
/* huge_ptep of dst_pte won't change as in child */
goto again;
}
hugetlb_install_folio(dst_vma, dst_pte, addr, new_folio);
hugetlb_install_folio(dst_vma, dst_pte, addr,
new_folio, src_pte_old);
spin_unlock(src_ptl);
spin_unlock(dst_ptl);
continue;
@ -5136,6 +5139,9 @@ again:
entry = huge_pte_wrprotect(entry);
}
if (!userfaultfd_wp(dst_vma))
entry = huge_pte_clear_uffd_wp(entry);
set_huge_pte_at(dst, addr, dst_pte, entry);
hugetlb_count_add(npages, dst);
}