+ mm-damon-reclaim-handle-ctx-allocation-failure.patch added to mm-hotfixes-unstable branch

+ mm-damon-reclaim-handle-ctx-allocation-failure.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/damon/reclaim: handle ctx allocation failure
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mm-damon-reclaim-handle-ctx-allocation-failure.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-reclaim-handle-ctx-allocation-failure.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via various
branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there most days

------------------------------------------------------
From: SeongJae Park <sj@kernel.org>
Subject: mm/damon/reclaim: handle ctx allocation failure
Date: Thu, 28 May 2026 17:01:02 -0700

Patch series "mm/damon/{reclaim,lru_sort}: handle ctx allocation failures".

DAMON_RECLAIM and DAMON_LRU_SORT could dereference NULL pointers if their
damon_ctx object allocations fail.  The bugs are expected to happen
infrequently because the allocations are arguably too small to fail on
common setups.  But theoretically they are possible and the consequences
are bad.  Fix those.

The issues were discovered [1] by Sashiko.


This patch (of 2):

DAMON_RECLAIM allocates the damon_ctx object for its kdamond in its init
function.  damon_reclaim_enabled_store() wrongly assumes the allocation
will always succeed once tried.  If the damon_ctx allocation was failed,
therefore, code execution reaches to damon_commit_ctx() while 'ctx' is
NULL.  As a result, it dereferences the NULL 'ctx' pointer.  Avoid the
NULL dereference by returning -ENOMEM if 'ctx' is NULL.

Link: https://lore.kernel.org/20260529000104.7006-2-sj@kernel.org
Link: https://lore.kernel.org/20260419014800.877-1-sj@kernel.org [1]
Fixes: 3f7a914ab9a5 ("mm/damon/reclaim: use damon_initialized()")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org> # 6.18.x
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/damon/reclaim.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/mm/damon/reclaim.c~mm-damon-reclaim-handle-ctx-allocation-failure
+++ a/mm/damon/reclaim.c
@@ -339,6 +339,10 @@ static int damon_reclaim_enabled_store(c
 	if (!damon_initialized())
 		return 0;
 
+	/* damon_modules_new_paddr_ctx_target() in the init function failed. */
+	if (!ctx)
+		return -ENOMEM;
+
 	return damon_reclaim_turn(enabled);
 }
 
_

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

mm-damon-ops-common-call-folio_test_lru-after-folio_get.patch
mm-damon-reclaim-handle-ctx-allocation-failure.patch
mm-damonn-lru_sort-handle-ctx-allocation-failure.patch
mm-damon-core-make-charge_addr_from-aware-of-end-address-exclusivity.patch
mm-damon-core-handle-min_region_sz-remaining-quota-as-empty.patch
mm-damon-core-merge-regions-after-applying-damos-schemes.patch
mm-damon-core-introduce-failed-region-quota-charge-ratio.patch
mm-damon-sysfs-schemes-implement-fail_charge_numdenom-files.patch
docs-mm-damon-design-document-fail_charge_numdenom.patch
docs-admin-guide-mm-damon-usage-document-fail_charge_numdenom-files.patch
docs-abi-damon-document-fail_charge_numdenom.patch
mm-damon-tests-core-kunit-test-fail_charge_numdenom-committing.patch
selftests-damon-_damon_sysfs-support-failed-region-quota-charge-ratio.patch
selftests-damon-drgn_dump_damon_status-support-failed-region-quota-charge-ratio.patch
selftests-damon-sysfspy-test-failed-region-quota-charge-ratio.patch
docs-mm-damon-maintainer-profile-add-ai-review-usage-guideline.patch
mm-damon-core-introduce-damon_ctx-paused.patch
mm-damon-sysfs-add-pause-file-under-context-dir.patch
docs-mm-damon-design-update-for-context-pause-resume-feature.patch
docs-admin-guide-mm-damon-usage-update-for-pause-file.patch
docs-abi-damon-update-for-pause-sysfs-file.patch
mm-damon-tests-core-kunit-test-pause-commitment.patch
selftests-damon-_damon_sysfs-support-pause-file-staging.patch
selftests-damon-drgn_dump_damon_status-dump-pause.patch
selftests-damon-sysfspy-check-pause-on-assert_ctx_committed.patch
selftests-damon-sysfspy-pause-damon-before-dumping-status.patch
mm-damon-introduce-damon_set_region_system_rams_default.patch
mm-damon-reclaim-cover-all-system-rams.patch
mm-damon-lru_sort-cover-all-system-rams.patch
mm-damon-core-remove-damon_set_region_biggest_system_ram_default.patch
mm-damon-stat-use-damon_set_region_system_rams_default.patch
docs-admin-guide-mm-damon-reclaim-update-for-entire-memory-monitoring.patch
docs-admin-guide-mm-damon-lru_sort-update-for-entire-memory-monitoring.patch
docs-admin-guide-mm-damon-usage-mark-scheme-filters-sysfs-dir-as-deprecated.patch
docs-abi-damon-mark-schemes-s-filters-deprecated.patch
mm-damon-reclaim-add-autotune_monitoring_intervals-parameter.patch
docs-admin-guide-mm-damon-reclaim-update-for-autotune_monitoring_intervals.patch
mm-damon-stat-add-a-parameter-for-reading-kdamond-pid.patch
docs-admin-guide-mm-damon-stat-document-kdamond_pid-parameter.patch
mm-damon-core-introduce-struct-damon_probe.patch
mm-damon-core-embed-damon_probe-objects-in-damon_ctx.patch
mm-damon-core-introduce-damon_filter.patch
mm-damon-core-commit-probes.patch
mm-damon-core-introduce-damon_region-probe_hits.patch
mm-damon-core-introduce-damon_ops-apply_probes.patch
mm-damon-core-do-data-attributes-monitoring.patch
mm-damon-paddr-support-data-attributes-monitoring.patch
mm-damon-sysfs-implement-probes-dir.patch
mm-damon-sysfs-implement-probe-dir.patch
mm-damon-sysfs-implement-filters-directory.patch
mm-damon-sysfs-implement-filter-dir.patch
mm-damon-sysfs-implement-filter-dir-files.patch
mm-damon-sysfs-setup-probes-on-damon-core-api-parameters.patch
mm-damon-sysfs-schemes-implement-tried_regions-r-probes.patch
mm-damon-sysfs-schemes-implement-probe-dir.patch
mm-damon-sysfs-schemes-implement-probe-hits-file.patch
mm-damon-trace-probe_hits.patch
selftests-damon-sysfssh-test-probes-dir.patch
docs-mm-damon-design-document-data-attributes-monitoring.patch
docs-admin-guide-mm-damon-usage-document-data-attributes-monitoring.patch
mm-damon-core-introduce-damon_filter_type_memcg.patch
mm-damon-paddr-support-damon_filter_type_memcg.patch
mm-damon-sysfs-add-filters-f-path-file.patch
mm-damon-sysfs-schemes-move-memcg_path_to_id-to-sysfs-common.patch
mm-damon-sysfs-setup-damon_filter-memcg_id-from-path.patch
docs-mm-damon-design-update-for-memcg-damon-filter.patch
docs-admin-guide-mm-damon-usage-update-for-memcg-damon-filter.patch
mm-damon-core-safely-handle-no-region-case-in-damon_set_regions.patch
mm-damon-core-do-not-use-region-out-of-a-loop-in-damon_set_regions.patch
samples-damon-mtier-replace-damon_add_region-with-damon_set_regions.patch
mm-damon-tests-vaddr-kunit-replace-damon_add_region-with-damon_set_regions.patch
mm-damon-core-hide-damon_add_region.patch
mm-damon-core-hide-damon_insert_region.patch
mm-damon-core-hide-damon_destroy_region.patch
mm-damon-core-add-kdamond_call-debug_sanity-check.patch
mm-damon-core-remove-damon_verify_nr_regions.patch
mm-damon-tests-core-kunit-add-damon_set_regions-test-cases.patch
selftests-damon-sysfspy-stop-kdamonds-before-failing.patch
selftests-damon-sysfssh-test-monitoring-intervals-goal-dir.patch
selftests-damon-sysfssh-test-addr_unit-file-existence.patch
selftests-damon-sysfssh-test-pause-file-existence.patch
mm-damon-core-trace-esz-at-first-setup.patch