[merged mm-stable] mm-damon-core-use-abs_diff-instead-of-abs.patch removed from -mm tree

The quilt patch titled
     Subject: mm/damon/core: use abs_diff() instead of abs()
has been removed from the -mm tree.  Its filename was
     mm-damon-core-use-abs_diff-instead-of-abs.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: SJ Park <[email protected]>
Subject: mm/damon/core: use abs_diff() instead of abs()
Date: Fri, 10 Jul 2026 06:46:36 -0700

Use of abs() in damon_merge_regions_of() could cause a silent integer
overflow since the macro casts unsigned int to signed int.  It is unlikely
to have such a large value for nr_accesses.  Even though it happens, the
user impact is just degraded monitoring results.  Users showing bad
monitoring results for weird setup is quite trivial.  But the code is
obviously wrong.  Use abs_diff() instead.

The issue was discovered [1] by Sashiko.

Link: https://lore.kernel.org/[email protected]
Link: https://lore.kernel.org/[email protected]/ [1]
Signed-off-by: SJ Park <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Liam R. Howlett <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---

 mm/damon/core.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/mm/damon/core.c~mm-damon-core-use-abs_diff-instead-of-abs
+++ a/mm/damon/core.c
@@ -3261,7 +3261,7 @@ static void damon_merge_regions_of(struc
 	struct damon_region *r, *prev = NULL, *next;
 
 	damon_for_each_region_safe(r, next, t) {
-		if (abs(r->nr_accesses - r->last_nr_accesses) > thres)
+		if (abs_diff(r->nr_accesses, r->last_nr_accesses) > thres)
 			r->age = 0;
 		else if ((r->nr_accesses == 0) != (r->last_nr_accesses == 0))
 			r->age = 0;
@@ -3269,7 +3269,7 @@ static void damon_merge_regions_of(struc
 			r->age++;
 
 		if (prev && prev->ar.end == r->ar.start &&
-		    abs(prev->nr_accesses - r->nr_accesses) <= thres &&
+		    abs_diff(prev->nr_accesses, r->nr_accesses) <= thres &&
 		    damon_sz_region(prev) + damon_sz_region(r) <= sz_limit)
 			damon_merge_two_regions(t, prev, r);
 		else
_

Patches currently in -mm which might be from [email protected] are

mm-damon-adjust-isolated-pages-stat-for-damos_migrate_hotcold.patch
samples-damon-mtier-error-out-for-zero-quota-goal-target-values.patch
mm-damon-lru_sort-error-out-for-10000-active_mem_bp.patch
mm-damon-reclaim-skip-damon_call-if-ctx-has-not-started.patch
mm-damon-lru_sort-skip-damon_call-if-ctx-has-not-started.patch
mm-damon-core-skip-aging-from-repeated-aggressive-merging.patch
mm-damon-core-hide-private-damon_region-fields.patch
mm-damon-core-hide-private-damon_target-fields.patch
mm-damon-core-hide-private-damos_quota_goal-fields.patch
mm-damon-core-hide-private-damos_quota-fields.patch
mm-damon-core-hide-private-damos_filter-fields.patch
mm-damon-core-hide-private-damos-fields.patch
mm-damon-core-hide-private-damon_filter-fields.patch
mm-damon-core-hide-private-damon_probe-fields.patch
mm-damon-sysfs-do-not-directly-access-damon_ctx-ops.patch
mm-damon-core-hide-core-private-damon_ctx-fields.patch
mm-damon-core-avoid-infinite-kdamond_merge_regions-internal-loop.patch
mm-damon-tests-core-kunit-catch-test-failure-in-test_merge_regions_of.patch
mm-damon-vaddr-drop-last-same-folio-access-check-optimization.patch
mm-damon-paddr-drop-last-same-folio-access-check-reuse-optimization.patch
mm-damon-sysfs-read-addr_unit-only-once-in-damon_sysfs_apply_inputs.patch
mm-damon-sysfs-read-ops_id-only-once-in-damon_sysfs_apply_inputs.patch
mm-damon-core-initialize-damos-last_applied.patch
mm-damon-core-kunit-check-region-count-before-testing-in-split_at.patch
mm-damon-vaddr-kunit-check-region-count-in-three_regions-test.patch
mm-damon-core-kunit-handle-region-split-failure-in-filter_out.patch
mm-damon-core-kunit-skip-wrong-dest-walk-in-commit_dests_for.patch
mm-damon-core-kunit-skip-wrong-quota-goal-walk-in-commit_quota_goals.patch
mm-damon-core-kunit-skip-wrong-region-walk-in-commit_target_regions.patch
mm-damon-ops-common-use-nr_accesses-moving-sum-for-quota-score.patch
mm-damon-core-handle-region-split-failure-in-apply_min_nr_regions.patch