+ tools-testing-selftests-mm-add-map_private-dev-zero-merge-tests.patch added to mm-new branch
Andrew Morton <[email protected]>
| Newsgroups | org.kernel.vger.mm-commits |
|---|---|
| Message-ID | <[email protected]> |
The patch titled
Subject: tools/testing/selftests/mm: add MAP_PRIVATE-/dev/zero merge tests
has been added to the -mm mm-new branch. Its filename is
tools-testing-selftests-mm-add-map_private-dev-zero-merge-tests.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/tools-testing-selftests-mm-add-map_private-dev-zero-merge-tests.patch
This patch will later appear in the mm-new branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews. Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.
The mm-new branch of mm.git is not included in linux-next
If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next
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------------------------------------------------------
From: "Lorenzo Stoakes (ARM)" <[email protected]>
Subject: tools/testing/selftests/mm: add MAP_PRIVATE-/dev/zero merge tests
Date: Mon, 20 Jul 2026 15:38:41 +0100
Assert that MAP_PRIVATE-mapped /dev/zero mappings behave like they are
anonymous.
We test both unfaulted and faulted/unfaulted merges - each with the
regions having page offset of 0, which would not merge if the mappings
were treated as if they were file-backed.
With the recent change that makes them behave as pure anonymous mappings,
the merges should succeed as their page offsets are equal to their virtual
page offsets.
Link: https://lore.kernel.org/20260720-b4-scalable-cow-virt-pgoff-v2-15-2d549757a76f@kernel.org
Signed-off-by: Lorenzo Stoakes (ARM) <[email protected]>
Cc: Alistair Popple <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Baolin Wang <[email protected]>
Cc: Barry Song <[email protected]>
Cc: Byungchul Park <[email protected]>
Cc: Chengming Zhou <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Dev Jain <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Gregory Price <[email protected]>
Cc: Harry Yoo <[email protected]>
Cc: "Huang, Ying" <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: Joshua Hahn <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Lance Yang <[email protected]>
Cc: Liam R. Howlett <[email protected]>
Cc: Matthew Brost <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Miaohe Lin <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: Nico Pache <[email protected]>
Cc: Pedro Falcato <[email protected]>
Cc: Peter Xu <[email protected]>
Cc: Rakie Kim <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Ryan Roberts <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: xu xin <[email protected]>
Cc: Zi Yan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---
tools/testing/selftests/mm/merge.c | 104 +++++++++++++++++++++++++++
1 file changed, 104 insertions(+)
--- a/tools/testing/selftests/mm/merge.c~tools-testing-selftests-mm-add-map_private-dev-zero-merge-tests
+++ a/tools/testing/selftests/mm/merge.c
@@ -1362,6 +1362,110 @@ TEST_F(merge, virt_and_page_offset_misma
ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr + 5 * page_size);
}
+TEST_F(merge, merge_map_private_dev_zero_unfaulted)
+{
+ struct procmap_fd *procmap = &self->procmap;
+ unsigned int page_size = self->page_size;
+ char *carveout = self->carveout;
+ char *ptr, *ptr2;
+ int fd_zero;
+
+ if (access("/dev/zero", F_OK))
+ SKIP(return, "No /dev/zero.");
+ fd_zero = open("/dev/zero", O_RDWR);
+ ASSERT_NE(fd_zero, -1);
+
+ /*
+ * Map two MAP_PRIVATE-/dev/zero VMAs next to one another with offset 0
+ * each.
+ *
+ * With these being made truly anonymous upon mapping, they will
+ * merge. If they were file-backed VMAs the page offsets would prevent
+ * merge:
+ *
+ * |-----||------| |-------------|
+ * | ptr || ptr2 | -> | ptr |
+ * |-----||------| |-------------|
+ */
+ ptr = mmap(carveout, 5 * page_size, PROT_READ | PROT_WRITE,
+ MAP_FIXED | MAP_PRIVATE, fd_zero, 0);
+ if (ptr == MAP_FAILED) {
+ close(fd_zero);
+ ASSERT_TRUE(false);
+ }
+ ptr2 = mmap(&carveout[5 * page_size], 5 * page_size,
+ PROT_READ | PROT_WRITE, MAP_FIXED | MAP_PRIVATE, fd_zero, 0);
+ if (ptr2 == MAP_FAILED) {
+ close(fd_zero);
+ ASSERT_TRUE(false);
+ }
+ close(fd_zero);
+
+ /* Assert that they merged. */
+ ASSERT_TRUE(find_vma_procmap(procmap, ptr));
+ ASSERT_EQ(procmap->query.vma_start, (unsigned long)ptr);
+ ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr + 10 * page_size);
+}
+
+TEST_F(merge, merge_map_private_dev_zero_faulted_unfaulted)
+{
+ struct procmap_fd *procmap = &self->procmap;
+ unsigned int page_size = self->page_size;
+ char *carveout = self->carveout;
+ char *ptr, *ptr2;
+ int fd_zero;
+
+ if (access("/dev/zero", F_OK))
+ SKIP(return, "No /dev/zero.");
+ fd_zero = open("/dev/zero", O_RDWR);
+ ASSERT_NE(fd_zero, -1);
+
+ /*
+ * Map a MAP_PRIVATE mapping of /dev/zero with page offset 0, then fault
+ * it in:
+ *
+ * |-------------------------------|
+ * | faulted |
+ * |-------------------------------|
+ */
+ ptr = mmap(carveout, 15 * page_size, PROT_READ | PROT_WRITE,
+ MAP_FIXED | MAP_PRIVATE, fd_zero, 0);
+ if (ptr == MAP_FAILED) {
+ close(fd_zero);
+ ASSERT_TRUE(false);
+ }
+ memset(ptr, 'x', 15 * page_size);
+
+ /*
+ * Unmap the middle:
+ *
+ * |---------| |---------|
+ * | faulted | | faulted |
+ * |---------| |---------|
+ */
+ ASSERT_EQ(munmap(&ptr[5 * page_size], 5 * page_size), 0);
+
+ /*
+ * Map in a new unfaulted mapping in the middle with page offset 0 -
+ * this should merge and would not if it were treated as a file rather
+ * than pure anon:
+ *
+ * |---------|-----------|---------|
+ * | faulted | unfaulted | faulted |
+ * |---------|-----------|---------|
+ */
+ ptr2 = mmap(&carveout[5 * page_size], 5 * page_size,
+ PROT_READ | PROT_WRITE, MAP_FIXED | MAP_PRIVATE,
+ fd_zero, 0);
+ close(fd_zero);
+ ASSERT_NE(ptr2, MAP_FAILED);
+
+ /* Assert that they merged. */
+ ASSERT_TRUE(find_vma_procmap(procmap, ptr));
+ ASSERT_EQ(procmap->query.vma_start, (unsigned long)ptr);
+ ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr + 15 * page_size);
+}
+
TEST_F(merge_with_fork, mremap_faulted_to_unfaulted_prev)
{
struct procmap_fd *procmap = &self->procmap;
_
Patches currently in -mm which might be from [email protected] are
mm-vmalloc-acquire-init_mm-lock-on-huge-vmap-to-avoid-ptdump-uaf.patch
x86-mm-pat-acquire-init_mm-write-lock-on-collapse-to-avoid-uaf.patch
x86-mm-pat-acquire-init_mm-read-lock-on-attribute-change-to-avoid-uaf.patch
mm-ptdump-always-stabilise-against-page-table-freeing-using-init_mm.patch
arm64-remove-redundant-concurrent-ptdump-uaf-mitigation.patch
mm-move-alloc-tag-to-mm.patch
mm-move-vma_start_pgoff-into-mmh-and-clean-up.patch
mm-add-kdoc-comments-for-vma_start-last_pgoff.patch
tools-testing-vma-use-vma_start_pgoff-in-merge-tests.patch
mm-introduce-and-use-vma_end_pgoff.patch
mm-rmap-update-mm-interval_treec-comments.patch
mm-rmap-parameterise-vma_interval_tree_-by-address_space.patch
mm-rmap-elide-unnecessary-static-inlines-in-interval_treec.patch
mm-rmap-rename-vma_interval_tree_-to-mapping_rmap_tree_.patch
mm-rmap-parameterise-anon_vma_interval_tree_-by-anon_vma.patch
mm-rmap-rename-anon_vma_interval_tree_-params-and-use-pgoff_t.patch
mm-rmap-rename-anon_vma_interval_tree_-to-anon_rmap_tree_.patch
maintainers-move-mm-interval_treec-to-rmap-section.patch
mm-vma-introduce-and-use-vmg_pages-vmg__pgoff.patch
mm-vma-clean-up-anon_vma_compatible.patch
mm-vma-refactor-vmg_adjust_set_range-for-clarity.patch
mm-vma-minor-cleanup-of-expand_.patch
mm-introduce-and-use-linear_page_delta.patch
mm-vma-use-vma_start_pgoff-linear_page_index-in-mm-code.patch
mm-prefer-vma__pgoff-to-vma-vm_pgoff-in-kernel.patch
mm-vma-remove-duplicative-vma_pgoff_offset-helper.patch
mm-use-linear_page_-consistently.patch
mm-vma-introduce-vma_assert_can_modify.patch
mm-vma-add-and-use-vma__pgoff.patch
mm-vma-move-__install_special_mapping-to-vmac.patch
mm-vma-make-vma_set_range-static-drop-insert_vm_struct-decl.patch
mm-vma-update-vma_shrink-to-not-pass-start-pgoff-parameters.patch
mm-vma-update-vmg_adjust_set_range-to-offset-pgoff-instead.patch
mm-vma-slightly-rework-the-anonymous-check-in-__mmap_new_vma.patch
mm-vma-introduce-and-use-vma_set_pgoff.patch
mm-vma-correct-incorrect-vmah-inclusion.patch
mm-vma-use-guard-clauses-in-can_vma_merge_.patch
tools-testing-vma-default-vma-mm-flag-bits-to-64-bit.patch
tools-testing-vma-output-compared-expression-on-assert_.patch
mm-introduce-vma_flags_can_grow-and-vma_can_grow.patch
mm-vma-update-do_mmap-to-use-vma_flags_t.patch
mm-convert-__get_unmapped_area-to-use-vma_flags_t.patch
mm-update-generic_get_unmapped_area-to-use-vma_flags_t.patch
mm-prefer-mm-def_vma_flags-in-mm-logic.patch
mm-vma-convert-vm_pgprot_modify-to-use-vma_flags_t-and-rename.patch
mm-vma-rename-vma_get_page_prot-to-vma_flags_to_page_prot.patch
mm-introduce-vma_get_page_prot-and-use-it.patch
mm-vma-update-create_init_stack_vma-to-use-vma_flags_t.patch
mm-vma-convert-miscellaneous-uses-of-vma-flags-in-core-mm.patch
mm-mlock-convert-mlock-code-to-use-vma_flags_t.patch
mm-mprotect-convert-mprotect-code-to-use-vma_flags_t.patch
mm-mremap-convert-mremap-code-to-use-vma_flags_t.patch
mm-mseal-remove-superfluous-comments-fix-confusion-around-mm.patch
mm-mseal-limit-scope-of-mseal-address-zero-to-address-zero.patch
mm-mseal-remove-further-superfluous-comments-do_mseal.patch
mm-vma-introduce-vma-virtual-page-offset-field-and-add-helpers.patch
mm-introduce-linear_virt_page_index.patch
mm-abstract-vma_address-and-introduce-vma_anon_address.patch
mm-update-print_bad_page_map-to-show-virtual-page-index.patch
mm-introduce-and-use-vma_filebacked_address.patch
mm-propagate-vma-virtual-page-offset-on-map-remap-split-merge.patch
mm-rmap-track-whether-the-page-vma-mapped-walk-is-anonymous.patch
mm-introduce-and-use-linear_folio_page_index.patch
mm-rmap-use-virt-pgoff-for-map_private-file-backed-anon-folios.patch
tools-testing-vma-expand-vma-merge-tests-to-assert-virt-pgoff.patch
tools-testing-selftests-mm-test-virtual-page-offset-merge-behaviour.patch
mm-vma-only-permit-map_private-dev-zero-to-be-mapped-anonymous.patch
mm-vma-make-map_private-mapped-dev-zero-mappings-truly-anonymous.patch
tools-testing-vma-add-test-to-assert-map_private-dev-zero-is-anon.patch
tools-testing-selftests-mm-add-map_private-dev-zero-merge-tests.patch