2 files changed, 133 insertions, 0 deletions
diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
index 0f31d850707d..2d5366196e30 100644
--- a/tools/testing/selftests/mm/Makefile
+++ b/tools/testing/selftests/mm/Makefile
@@ -149,6 +149,7 @@ TEST_PROGS += ksft_gup_test.sh
 TEST_PROGS += ksft_hmm.sh
 TEST_PROGS += ksft_hugetlb.sh
 TEST_PROGS += ksft_hugevm.sh
+TEST_PROGS += ksft_kmemleak_confirm.sh
 TEST_PROGS += ksft_kmemleak_dedup.sh
 TEST_PROGS += ksft_ksm.sh
 TEST_PROGS += ksft_ksm_numa.sh
diff --git a/tools/testing/selftests/mm/ksft_kmemleak_confirm.sh b/tools/testing/selftests/mm/ksft_kmemleak_confirm.sh
new file mode 100755
index 000000000000..3a8576e835c8
--- /dev/null
+++ b/tools/testing/selftests/mm/ksft_kmemleak_confirm.sh
@@ -0,0 +1,132 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Functional test for kmemleak's N-consecutive-scan leak confirmation
+# (the min_unref_scans module parameter).
+#
+# kmemleak only reports an object once it has stayed unreferenced for
+# min_unref_scans consecutive scans. The default of 1 reports on the first
+# scan (historical behaviour); higher values filter transient false
+# positives where a live object's only reference is briefly invisible to a
+# single scan (e.g. an RCU tree update in flight while the scan runs). The
+# test loads samples/kmemleak's helper module to create orphan allocations
+# and, counting only those orphans (matched by their [kmemleak_test]
+# backtrace so unrelated leaks already present on the system are ignored),
+# checks that:
+#   - a freshly allocated object is greyed on its first scan (its checksum
+#     settles then), so nothing can be reported before that priming scan;
+#     each case below primes once first,
+#   - with the default threshold (min_unref_scans=1) one scan after priming
+#     reports the orphans,
+#   - raising the threshold to 2 needs two scans after priming: one is not
+#     enough, the second reports,
+#   - the parameter reads back what was written.
+#
+# The "one post-prime scan is not enough at min_unref_scans=2" check is the
+# core regression test: raising min_unref_scans must push the report
+# strictly later. Like ksft_kmemleak_dedup.sh, if the module yields no
+# detectable orphan at all in the running environment the test skips rather
+# than failing.
+#
+# Author: Breno Leitao <leitao@debian.org>
+
+# KTAP output helpers (ktap_skip_all, ktap_exit_fail_msg, ktap_test_pass, ...).
+DIR="$(dirname "$(readlink -f "$0")")"
+# shellcheck source=../kselftest/ktap_helpers.sh
+source "${DIR}"/../kselftest/ktap_helpers.sh
+
+KMEMLEAK=/sys/kernel/debug/kmemleak
+PARAM=/sys/module/kmemleak/parameters/min_unref_scans
+MODULE=kmemleak-test
+AGE=6		# seconds; must exceed kmemleak's 5s minimum object age
+
+ktap_print_header
+
+[ "$(id -u)" -eq 0 ] || { ktap_skip_all "must run as root"; exit "$KSFT_SKIP"; }
+[ -r "$KMEMLEAK" ] ||
+	{ ktap_skip_all "no kmemleak debugfs (CONFIG_DEBUG_KMEMLEAK)"; exit "$KSFT_SKIP"; }
+[ -w "$PARAM" ] ||
+	{ ktap_skip_all "min_unref_scans module parameter not present"; exit "$KSFT_SKIP"; }
+modinfo "$MODULE" >/dev/null 2>&1 ||
+	{ ktap_skip_all "$MODULE not built (CONFIG_SAMPLE_KMEMLEAK)"; exit "$KSFT_SKIP"; }
+
+# kmemleak can be present but disabled at runtime (kmemleak=off boot arg,
+# or it self-disabled after an internal error); a "scan" then returns
+# EPERM. Probe once and skip if so.
+echo scan > "$KMEMLEAK" 2>/dev/null ||
+	{ ktap_skip_all "kmemleak is disabled (check dmesg or kmemleak= boot arg)"; exit "$KSFT_SKIP"; }
+
+prev=$(cat "$PARAM")
+# shellcheck disable=SC2317  # invoked indirectly via trap
+cleanup() {
+	echo "$prev" > "$PARAM" 2>/dev/null		# restore the parameter
+	echo scan=on > "$KMEMLEAK" 2>/dev/null		# re-enable auto scan
+	rmmod "$MODULE" 2>/dev/null
+	echo clear > "$KMEMLEAK" 2>/dev/null
+}
+trap cleanup EXIT
+
+# Stop the automatic scan thread: only our manual scans should advance an
+# object's consecutive-unreferenced run. An auto scan landing between two
+# manual scans would change the result and make the test flaky.
+echo scan=off > "$KMEMLEAK" 2>/dev/null
+
+# Create a fresh, aged set of orphan objects from the helper module's init
+# path (its kmalloc/vmalloc/percpu allocations are dropped right away).
+# Pre-existing reported leaks are greyed first ("clear") so only our
+# orphans are counted. The module is left loaded on purpose: once it is
+# unloaded its symbols are gone, so the orphan backtraces no longer resolve
+# to [kmemleak_test] and could not be matched below.
+gen_orphans() {
+	rmmod "$MODULE" 2>/dev/null
+	echo clear > "$KMEMLEAK"
+	modprobe "$MODULE" ||
+		{ ktap_skip_all "failed to load $MODULE"; exit "$KSFT_SKIP"; }
+	sleep "$AGE"
+}
+
+scan() { echo scan > "$KMEMLEAK"; }
+
+# Number of helper-module orphans currently reported by kmemleak. Matching
+# the module's own backtrace ([kmemleak_test]) keeps the count immune to
+# unrelated leaks on the running system. kmemleak only lists an object here
+# once it has been reported, so this reflects the confirmation gating.
+count_orphans() {
+	c=$(grep -c '\[kmemleak_test\]' "$KMEMLEAK" 2>/dev/null)
+	echo "${c:-0}"
+}
+
+# 0) the parameter reads back what was written.
+echo 3 > "$PARAM"
+[ "$(cat "$PARAM")" = "3" ] || ktap_exit_fail_msg "min_unref_scans did not read back as 3"
+
+# Priming scan: kmemleak greys a freshly allocated object on its first scan
+# (its checksum settles then), so nothing can be reported until a second
+# scan. Every case below runs this priming scan before counting.
+prime() { scan; }
+
+# 1) min_unref_scans=1 (default): one scan after priming reports the
+#    orphans. This also establishes that the helper produces detectable
+#    orphans here.
+echo 1 > "$PARAM"
+gen_orphans
+prime
+scan
+first=$(count_orphans)
+[ "$first" -gt 0 ] ||
+	{ ktap_skip_all "$MODULE produced no detectable orphans (cannot test min_unref_scans)"; exit "$KSFT_SKIP"; }
+
+# 2) min_unref_scans=2: after priming, one scan is not enough (still
+#    gated), the second reports. The gated-scan-zero check is the core
+#    regression.
+echo 2 > "$PARAM"
+gen_orphans
+prime
+scan; s1=$(count_orphans)
+scan; s2=$(count_orphans)
+[ "$s1" -eq 0 ] || ktap_exit_fail_msg "min_unref_scans=2: $s1 orphan(s) after 1 post-prime scan (must be 0)"
+[ "$s2" -gt 0 ] || ktap_exit_fail_msg "min_unref_scans=2: no report after 2 post-prime scans (false negative)"
+
+ktap_set_plan 1
+ktap_test_pass "min_unref_scans=1 reported $first orphan(s) one scan after priming; =2 held them one scan longer ($s1 after one scan, $s2 after two); param read-back ok"
+ktap_finished