[merged mm-stable] selftests-mm-fix-uffd-move-pmd-test-crash-on-64k-base-page-systems.patch removed from -mm tree

[merged mm-stable] selftests-mm-fix-uffd-move-pmd-test-crash-on-64k-base-page-systems.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: selftests/mm: fix uffd move-pmd test crash on 64K base page systems
has been removed from the -mm tree.  Its filename was
     selftests-mm-fix-uffd-move-pmd-test-crash-on-64k-base-page-systems.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: "Zenghui Yu (Huawei)" <zenghui.yu@linux.dev>
Subject: selftests/mm: fix uffd move-pmd test crash on 64K base page systems
Date: Mon, 12 Oct 2026 00:35:27 +0800

uffd_move_pmd_test()/uffd_move_test_common() splits the test area into
chunks of chunk_size and moves them one by one.  On arm64 with 64K base
pages the chunk_size (read_pmd_pagesize()) is 512MB, which is larger than
the whole 32MB (UFFD_TEST_MEM_SIZE) test area:

  step_count = nr_pages / (chunk_size / page_size) == 0

Because chunk_size > page_size, the test then aligns both areas up to
512MB, which points far outside of the 32MB mappings, and decrements
step_count, which underflows to ULONG_MAX.  The verification loop then
runs away and the first dereference of area_src faults with a SIGSEGV.

Skip the test when a single chunk cannot fit into the test area.

Link: https://lore.kernel.org/20261011163527.95988-1-zenghui.yu@linux.dev
Fixes: a2bf6a9ca805 ("selftests/mm: add UFFDIO_MOVE ioctl test")
Signed-off-by: Zenghui Yu (Huawei) <zenghui.yu@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jose A. Perez de Azpillaga <azpijr@gmail.com>
Tested-by: Sarthak Sharma <sarthak.sharma@arm.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
---

 tools/testing/selftests/mm/uffd-unit-tests.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/tools/testing/selftests/mm/uffd-unit-tests.c~selftests-mm-fix-uffd-move-pmd-test-crash-on-64k-base-page-systems
+++ a/tools/testing/selftests/mm/uffd-unit-tests.c
@@ -1937,6 +1937,11 @@ uffd_move_test_common(uffd_global_test_o
 
 	args.gopts = gopts;
 
+	if (chunk_size > gopts->nr_pages * gopts->page_size) {
+		uffd_test_skip("chunk size does not fit in the test area");
+		return;
+	}
+
 	/* Prevent source pages from being mapped more than once */
 	if (madvise(gopts->area_src, gopts->nr_pages * gopts->page_size, MADV_DONTFORK))
 		err("madvise(MADV_DONTFORK) failure");
_

Patches currently in -mm which might be from zenghui.yu@linux.dev are

mm-page_alloc-mark-pages-freed-by-__free_pages_core-as-not-tagged.patch