diff options
| author | Kiryl Shutsemau (Meta) <kas@kernel.org> | 2026-07-08 12:14:08 +0100 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2026-08-04 19:18:37 -0700 |
| commit | 763f43865fc4136562ae84542604081f7989a951 (patch) | |
| tree | 2d40c3d149e3acb949a90559fe7e3d3a7d619576 /include | |
| parent | 9cf3c554acbdd3661e2ae5043de842a551c5d0ed (diff) | |
mm: preserve RWP marker across PTE rewrites
The uffd PTE bit must survive any kernel path that rewrites a PTE on a
VM_UFFD_RWP VMA, otherwise the marker that carries PAGE_NONE semantics is
silently dropped and the next access leaks past RWP tracking. Wire the
preservation through every path that rewrites a VM_UFFD_RWP PTE.
Swap and device-exclusive: do_swap_page(), restore_exclusive_pte(), and
unuse_pte() (swapoff()) re-apply PAGE_NONE when the swap PTE carries the
uffd bit and the VMA has VM_UFFD_RWP.
Migration: remove_migration_pte() and remove_migration_pmd() do the same
after the migration entry is replaced with a real PTE/PMD.
Fork: __copy_present_ptes(), copy_present_page(), copy_nonpresent_pte(),
copy_huge_pmd(), copy_huge_non_present_pmd(), and
copy_hugetlb_page_range() keep the uffd bit on the child when the
destination VMA has VM_UFFD_RWP, matching the existing VM_UFFD_WP
handling. Add VM_UFFD_RWP to VM_COPY_ON_FORK so the flag itself
propagates.
mprotect(): change_pte_range() and change_huge_pmd() restore PAGE_NONE
after pte_modify()/pmd_modify() have recomputed the base protection from a
(possibly user-changed) vm_page_prot. pte_modify() preserves _PAGE_UFFD,
so the bit stays; we just have to force PAGE_NONE back on top.
Link: https://lore.kernel.org/20260708111417.173443-8-kirill@shutemov.name
Signed-off-by: Kiryl Shutsemau <kas@kernel.org>
Assisted-by: Claude:claude-opus-4-6
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: James Houghton <jthoughton@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/mm.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 170f21f28c77..be4457269a38 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -684,7 +684,8 @@ enum { * only and thus cannot be reconstructed on page * fault. */ -#define VM_COPY_ON_FORK (VM_PFNMAP | VM_MIXEDMAP | VM_UFFD_WP | VM_MAYBE_GUARD) +#define VM_COPY_ON_FORK (VM_PFNMAP | VM_MIXEDMAP | VM_UFFD_WP | VM_UFFD_RWP | \ + VM_MAYBE_GUARD) /* * mapping from the currently active vm_flags protection bits (the |