The patch titled
Subject: mm/shmem: take care of UFFDIO_COPY_MODE_WP
has been added to the -mm tree. Its filename is
mm-shmem-take-care-of-uffdio_copy_mode_wp.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-shmem-take-care-of-uffdio_copy_mode_wp.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-shmem-take-care-of-uffdio_copy_mode_wp.patch
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The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: Peter Xu <peterx@xxxxxxxxxx>
Subject: mm/shmem: take care of UFFDIO_COPY_MODE_WP
Pass wp_copy into shmem_mfill_atomic_pte() through the stack, then apply
the UFFD_WP bit properly when the UFFDIO_COPY on shmem is with
UFFDIO_COPY_MODE_WP. wp_copy lands mfill_atomic_install_pte() finally.
Note: we must do pte_wrprotect() if !writable in
mfill_atomic_install_pte(), as mk_pte() could return a writable pte (e.g.,
when VM_SHARED on a shmem file).
Link: https://lkml.kernel.org/r/20220405014841.14185-1-peterx@xxxxxxxxxx
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Jerome Glisse <jglisse@xxxxxxxxxx>
Cc: "Kirill A . Shutemov" <kirill@xxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
Cc: Nadav Amit <nadav.amit@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/shmem_fs.h | 4 ++--
mm/shmem.c | 4 ++--
mm/userfaultfd.c | 23 ++++++++++++++++++-----
3 files changed, 22 insertions(+), 9 deletions(-)
--- a/include/linux/shmem_fs.h~mm-shmem-take-care-of-uffdio_copy_mode_wp
+++ a/include/linux/shmem_fs.h
@@ -145,11 +145,11 @@ extern int shmem_mfill_atomic_pte(struct
struct vm_area_struct *dst_vma,
unsigned long dst_addr,
unsigned long src_addr,
- bool zeropage,
+ bool zeropage, bool wp_copy,
struct page **pagep);
#else /* !CONFIG_SHMEM */
#define shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr, \
- src_addr, zeropage, pagep) ({ BUG(); 0; })
+ src_addr, zeropage, wp_copy, pagep) ({ BUG(); 0; })
#endif /* CONFIG_SHMEM */
#endif /* CONFIG_USERFAULTFD */
--- a/mm/shmem.c~mm-shmem-take-care-of-uffdio_copy_mode_wp
+++ a/mm/shmem.c
@@ -2313,7 +2313,7 @@ int shmem_mfill_atomic_pte(struct mm_str
struct vm_area_struct *dst_vma,
unsigned long dst_addr,
unsigned long src_addr,
- bool zeropage,
+ bool zeropage, bool wp_copy,
struct page **pagep)
{
struct inode *inode = file_inode(dst_vma->vm_file);
@@ -2386,7 +2386,7 @@ int shmem_mfill_atomic_pte(struct mm_str
goto out_release;
ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
- page, true, false);
+ page, true, wp_copy);
if (ret)
goto out_delete_from_cache;
--- a/mm/userfaultfd.c~mm-shmem-take-care-of-uffdio_copy_mode_wp
+++ a/mm/userfaultfd.c
@@ -78,10 +78,19 @@ int mfill_atomic_install_pte(struct mm_s
* Always mark a PTE as write-protected when needed, regardless of
* VM_WRITE, which the user might change.
*/
- if (wp_copy)
+ if (wp_copy) {
_dst_pte = pte_mkuffd_wp(_dst_pte);
- else if (writable)
+ writable = false;
+ }
+
+ if (writable)
_dst_pte = pte_mkwrite(_dst_pte);
+ else
+ /*
+ * We need this to make sure write bit removed; as mk_pte()
+ * could return a pte with write bit set.
+ */
+ _dst_pte = pte_wrprotect(_dst_pte);
dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
@@ -96,7 +105,12 @@ int mfill_atomic_install_pte(struct mm_s
}
ret = -EEXIST;
- if (!pte_none(*dst_pte))
+ /*
+ * We allow to overwrite a pte marker: consider when both MISSING|WP
+ * registered, we firstly wr-protect a none pte which has no page cache
+ * page backing it, then access the page.
+ */
+ if (!pte_none_mostly(*dst_pte))
goto out_unlock;
if (page_in_cache) {
@@ -480,11 +494,10 @@ static __always_inline ssize_t mfill_ato
err = mfill_zeropage_pte(dst_mm, dst_pmd,
dst_vma, dst_addr);
} else {
- VM_WARN_ON_ONCE(wp_copy);
err = shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma,
dst_addr, src_addr,
mode != MCOPY_ATOMIC_NORMAL,
- page);
+ wp_copy, page);
}
return err;
_
Patches currently in -mm which might be from peterx@xxxxxxxxxx are
mm-introduce-pte_marker-swap-entry.patch
mm-teach-core-mm-about-pte-markers.patch
mm-check-against-orig_pte-for-finish_fault.patch
mm-uffd-pte_marker_uffd_wp.patch
mm-shmem-take-care-of-uffdio_copy_mode_wp.patch
mm-shmem-handle-uffd-wp-special-pte-in-page-fault-handler.patch
mm-shmem-persist-uffd-wp-bit-across-zapping-for-file-backed.patch
mm-shmem-allow-uffd-wr-protect-none-pte-for-file-backed-mem.patch
mm-shmem-allows-file-back-mem-to-be-uffd-wr-protected-on-thps.patch
mm-shmem-handle-uffd-wp-during-fork.patch
mm-hugetlb-introduce-huge-pte-version-of-uffd-wp-helpers.patch
mm-hugetlb-hook-page-faults-for-uffd-write-protection.patch
mm-hugetlb-take-care-of-uffdio_copy_mode_wp.patch
mm-hugetlb-handle-uffdio_writeprotect.patch
mm-hugetlb-handle-pte-markers-in-page-faults.patch
mm-hugetlb-allow-uffd-wr-protect-none-ptes.patch
mm-hugetlb-only-drop-uffd-wp-special-pte-if-required.patch
mm-hugetlb-handle-uffd-wp-during-fork.patch
mm-khugepaged-dont-recycle-vma-pgtable-if-uffd-wp-registered.patch
mm-pagemap-recognize-uffd-wp-bit-for-shmem-hugetlbfs.patch
mm-uffd-enable-write-protection-for-shmem-hugetlbfs.patch
mm-enable-pte-markers-by-default.patch
selftests-uffd-enable-uffd-wp-for-shmem-hugetlbfs.patch
