+ userfaultfd-ensure-mremap_userfaultfd_fail-releases-mmap_changing.patch added to mm-new branch

+ userfaultfd-ensure-mremap_userfaultfd_fail-releases-mmap_changing.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: userfaultfd: ensure mremap_userfaultfd_fail() releases mmap_changing
has been added to the -mm mm-new branch.  Its filename is
     userfaultfd-ensure-mremap_userfaultfd_fail-releases-mmap_changing.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/userfaultfd-ensure-mremap_userfaultfd_fail-releases-mmap_changing.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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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

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and is updated there most days

------------------------------------------------------
From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
Subject: userfaultfd: ensure mremap_userfaultfd_fail() releases mmap_changing
Date: Wed, 13 May 2026 11:14:16 +0300

Sashiko says:

  mremap_userfaultfd_prep() increments ctx->mmap_changing to stall
  concurrent operations, but mremap_userfaultfd_fail() does not
  decrement it before dropping the context reference.

If an mremap operation fails, ctx->mmap_changing remains elevated. This
will causes subsequent userfaultfd operations like a UFFDIO_COPY to fail
with -EAGAIN.

Decrement ctx->mmap_changing in mremap_userfaultfd_fail().

Link: https://sashiko.dev/#/patchset/20260430113512.115938-1-rppt@kernel.org
Link: https://lore.kernel.org/20260513081416.495963-1-rppt@kernel.org
Fixes: df2cc96e7701 ("userfaultfd: prevent non-cooperative events vs mcopy_atomic races")
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Peter Xu <peterx@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/userfaultfd.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/userfaultfd.c~userfaultfd-ensure-mremap_userfaultfd_fail-releases-mmap_changing
+++ a/fs/userfaultfd.c
@@ -786,6 +786,8 @@ void mremap_userfaultfd_fail(struct vm_u
 	if (!ctx)
 		return;
 
+	atomic_dec(&ctx->mmap_changing);
+	VM_WARN_ON_ONCE(atomic_read(&ctx->mmap_changing) < 0);
 	userfaultfd_ctx_put(ctx);
 }
 
_

Patches currently in -mm which might be from rppt@kernel.org are

maintainers-add-tree-for-kdump-and-kexec.patch
maintainers-add-kexec-list-to-live-update-entry.patch
sh-fix-fallout-from-zero_page-consolidation.patch
selftests-mm-hugetlb-read-hwpoison-add-sigbus-handler.patch
selftests-mm-migration-dont-assume-huge-page-is-twomeg.patch
selftests-mm-migration-make-nthreads-represent-number-of-working-threads.patch
selftests-mm-migration-properly-cleanup-forked-processes.patch
selftests-mm-run_vmtestssh-dont-gate-thp-and-ksm-tests-on-have_hugepages.patch
selftests-mm-merge-map_hugetlb-into-hugepage-mmap.patch
selftests-mm-rename-hugepage-tests-to-hugetlb.patch
selftests-mm-hugetlb-shm-use-kselftest-framework.patch
selftests-mm-hugetlb-vmemmap-use-kselftest-framework.patch
selftests-mm-hugetlb-madvise-use-kselftest-framework.patch
selftests-mm-hugetlb_madv_vs_map-use-kselftest-framework.patch
selftests-mm-hugetlb-read-hwpoison-use-kselftest-framework.patch
selftests-mm-khugepaged-group-tests-in-an-array.patch
selftests-mm-khugepaged-use-ksefltest-framework.patch
selftests-mm-khugepaged-use-ksefltest-framework-fix.patch
selftests-mm-ksm_tests-use-kselftest-framework.patch
selftests-mm-protection_keys-use-descriptive-test-names-in-the-output.patch
selftests-mm-protection_keys-use-kselftest-framework.patch
selftests-mm-uffd-common-use-kselftest-framework.patch
selftests-mm-uffd-stress-use-kselftest-framework.patch
selftests-mm-uffd-unit-tests-use-kselftest-framework.patch
selftests-mm-va_high_addr_switch-use-kselftest-framework.patch
selftests-mm-add-atexit-and-signal-handlers-to-thp_settings.patch
selftests-mm-rename-thp_settings-to-hugepage_settings.patch
selftests-mm-move-hugetlb-helpers-to-hugepage_settings.patch
selftests-mm-hugepage_settings-use-unsigned-long-in-detect_hugetlb_page_size.patch
selftests-mm-hugepage_settings-add-apis-to-get-and-set-nr_hugepages.patch
selftests-mm-hugepage_settings-rename-and-rework-get_free_hugepages.patch
selftests-mm-hugepage_settings-add-apis-for-hugetlb-setup-and-teardown.patch
selftests-mm-move-read_file-read_num-and-write_num-to-vm_util.patch
selftests-mm-vm_util-add-helpers-to-set-and-restore-shm-limits.patch
selftests-mm-compaction_test-use-hugetlb-helpers.patch
selftests-mm-cow-add-setup-of-hugetlb-pages.patch
selftests-mm-gup_longterm-add-setup-of-hugetlb-pages.patch
selftests-mm-gup_test-add-setup-of-hugetlb-pages.patch
selftests-mm-hmm-tests-add-setup-of-hugetlb-pages.patch
selftests-mm-hugepage_dio-add-setup-of-hugetlb-pages.patch
selftests-mm-hugetlb_fault_after_madv-add-setup-of-hugetlb-pages.patch
selftests-mm-hugetlb-madvise-add-setup-of-hugetlb-pages.patch
selftests-mm-hugetlb_madv_vs_map-add-setup-of-hugetlb-pages.patch
selftests-mm-hugetlb-mmap-add-setup-of-hugetlb-pages.patch
selftests-mm-hugetlb-mremap-add-setup-of-hugetlb-pages.patch
selftests-mm-hugetlb-shm-add-setup-of-hugetlb-pages.patch
selftests-mm-hugetlb-soft-offline-add-setup-of-hugetlb-pages.patch
selftests-mm-hugetlb-vmemmap-add-setup-of-hugetlb-pages.patch
selftests-mm-migration-add-setup-of-hugetlb-pages.patch
selftests-mm-pagemap_ioctl-add-setup-of-hugetlb-pages.patch
selftests-mm-protection_keys-use-library-code-for-hugetlb-setup.patch
selftests-mm-thuge-gen-add-setup-of-hugetlb-pages.patch
selftests-mm-uffd-stress-use-hugetlb_save-and-alloc-huge-pages.patch
selftests-mm-uffd-unit-tests-add-setup-of-hugetlb-pages.patch
selftests-mm-uffd-wp-mremap-add-setup-of-hugetlb-pages.patch
selftests-mm-va_high_addr_switch-add-setup-of-hugetlb-pages.patch
selftests-mm-va_high_addr_switchsh-drop-huge-pages-setup.patch
selftests-mm-run_vmtestssh-free-memory-if-available-memory-is-low.patch
selftests-mm-run_vmtestssh-drop-detection-and-setup-of-hugetlb.patch
userfaultfd-ensure-mremap_userfaultfd_fail-releases-mmap_changing.patch