AI Trajectory

null

{
  "EnableConfigs": [
    "DEBUG_KMEMLEAK"
  ],
  "FocusSymbols": [
    "kmemleak_scan"
  ],
  "Reasoning": "The patch introduces functional changes to the kmemleak scanning logic by adding a new module parameter `min_unref_scans` and modifying `kmemleak_scan` to require a minimum number of consecutive unreferenced scans before reporting an object. This modifies the core state machine of the leak detector.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit bd7f4362253e7b5bd9348f17d8a8b580701c84ec\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Fri Jun 26 22:42:07 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/Documentation/dev-tools/kmemleak.rst b/Documentation/dev-tools/kmemleak.rst\nindex 7d784e03f3f9d5..a8a83bc69ceb88 100644\n--- a/Documentation/dev-tools/kmemleak.rst\n+++ b/Documentation/dev-tools/kmemleak.rst\n@@ -198,6 +198,14 @@ systems, because of pointers temporarily stored in CPU registers or\n stacks. Kmemleak defines MSECS_MIN_AGE (defaulting to 1000) representing\n the minimum age of an object to be reported as a memory leak.\n \n+The ``min_unref_scans`` module parameter (default 1) requires an object to\n+be seen unreferenced in that many consecutive scans before it is reported.\n+Keeping it at 1 preserves the historical behaviour; higher values filter\n+the transient false positives described above, at the cost of delaying\n+genuine reports by up to that many scans. It can be set at boot with\n+``kmemleak.min_unref_scans=\u003cn\u003e`` or at run-time via\n+``/sys/module/kmemleak/parameters/min_unref_scans``.\n+\n Limitations and Drawbacks\n -------------------------\n \ndiff --git a/mm/kmemleak.c b/mm/kmemleak.c\nindex 7c7ba17ce7af00..5b14ccb36f95ba 100644\n--- a/mm/kmemleak.c\n+++ b/mm/kmemleak.c\n@@ -151,6 +151,8 @@ struct kmemleak_object {\n \tint min_count;\n \t/* the total number of pointers found pointing to this object */\n \tint count;\n+\t/* consecutive scans the object has been seen unreferenced */\n+\tunsigned int unref_scans;\n \t/* checksum for detecting modified objects */\n \tu32 checksum;\n \tdepot_stack_handle_t trace_handle;\n@@ -232,6 +234,9 @@ static unsigned long max_percpu_addr;\n static struct task_struct *scan_thread;\n /* used to avoid reporting of recently allocated objects */\n static unsigned long jiffies_min_age;\n+/* consecutive scans an object must stay unreferenced before reporting */\n+static unsigned int min_unref_scans = 1;\n+module_param(min_unref_scans, uint, 0644);\n static unsigned long jiffies_last_scan;\n /* delay between automatic memory scannings */\n static unsigned long jiffies_scan_wait;\n@@ -687,6 +692,7 @@ static struct kmemleak_object *__alloc_object(gfp_t gfp)\n \tatomic_set(\u0026object-\u003euse_count, 1);\n \tobject-\u003eexcess_ref = 0;\n \tobject-\u003ecount = 0;\t\t\t/* white color initially */\n+\tobject-\u003eunref_scans = 0;\n \tobject-\u003echecksum = 0;\n \tobject-\u003edel_state = 0;\n \n@@ -1833,6 +1839,9 @@ static void kmemleak_scan(void)\n \t\t\t\t__paint_it(object, KMEMLEAK_BLACK);\n \t\t}\n \n+\t\t/* referenced last scan: restart the unreferenced run */\n+\t\tif (!color_white(object))\n+\t\t\tobject-\u003eunref_scans = 0;\n \t\t/* reset the reference count (whiten the object) */\n \t\tobject-\u003ecount = 0;\n \t\tif (color_gray(object) \u0026\u0026 get_object(object))\n@@ -1968,8 +1977,9 @@ static void kmemleak_scan(void)\n \t\traw_spin_lock_irq(\u0026object-\u003elock);\n \t\ttrace_handle = 0;\n \t\tdedup_print = false;\n-\t\tif (unreferenced_object(object) \u0026\u0026\n-\t\t    !(object-\u003eflags \u0026 OBJECT_REPORTED)) {\n+\t\tif (!(object-\u003eflags \u0026 OBJECT_REPORTED) \u0026\u0026\n+\t\t    unreferenced_object(object) \u0026\u0026\n+\t\t    ++object-\u003eunref_scans \u003e= min_unref_scans) {\n \t\t\tobject-\u003eflags |= OBJECT_REPORTED;\n \t\t\tif (kmemleak_verbose) {\n \t\t\t\ttrace_handle = object-\u003etrace_handle;\ndiff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile\nindex e6df968f0971c8..84026b62a1ae5e 100644\n--- a/tools/testing/selftests/mm/Makefile\n+++ b/tools/testing/selftests/mm/Makefile\n@@ -150,6 +150,7 @@ TEST_PROGS += ksft_gup_test.sh\n TEST_PROGS += ksft_hmm.sh\n TEST_PROGS += ksft_hugetlb.sh\n TEST_PROGS += ksft_hugevm.sh\n+TEST_PROGS += ksft_kmemleak_confirm.sh\n TEST_PROGS += ksft_kmemleak_dedup.sh\n TEST_PROGS += ksft_ksm.sh\n TEST_PROGS += ksft_ksm_numa.sh\ndiff --git a/tools/testing/selftests/mm/ksft_kmemleak_confirm.sh b/tools/testing/selftests/mm/ksft_kmemleak_confirm.sh\nnew file mode 100755\nindex 00000000000000..34ab64bc6948f8\n--- /dev/null\n+++ b/tools/testing/selftests/mm/ksft_kmemleak_confirm.sh\n@@ -0,0 +1,111 @@\n+#!/bin/bash\n+# SPDX-License-Identifier: GPL-2.0\n+#\n+# Functional test for kmemleak's N-consecutive-scan leak confirmation\n+# (the min_unref_scans module parameter).\n+#\n+# kmemleak only reports an object once it has stayed unreferenced for\n+# min_unref_scans consecutive scans. The default of 1 reports on the first\n+# scan (historical behaviour); higher values filter transient false\n+# positives where a live object's only reference is briefly invisible to a\n+# single scan (e.g. an RCU tree update in flight while the scan runs). The\n+# test loads samples/kmemleak's helper module to create orphan allocations\n+# and, counting only those orphans (matched by their [kmemleak_test]\n+# backtrace so unrelated leaks already present on the system are ignored),\n+# checks that:\n+#   - min_unref_scans=1 reports them on the first scan,\n+#   - min_unref_scans=2 reports nothing on the first scan but does on the\n+#     second,\n+#   - the parameter reads back what was written.\n+#\n+# The \"nothing on the first scan\" check is the core regression test: with\n+# min_unref_scans=2 no object can be reported in fewer than two scans. Like\n+# ksft_kmemleak_dedup.sh, if the module yields no detectable orphan at all\n+# in the running environment the test skips rather than failing.\n+#\n+# Author: Breno Leitao \u003cleitao@debian.org\u003e\n+\n+ksft_skip=4\n+KMEMLEAK=/sys/kernel/debug/kmemleak\n+PARAM=/sys/module/kmemleak/parameters/min_unref_scans\n+MODULE=kmemleak-test\n+AGE=6\t\t# seconds; must exceed kmemleak's 5s minimum object age\n+\n+skip() { echo \"SKIP: $*\"; exit $ksft_skip; }\n+fail() { echo \"FAIL: $*\"; exit 1; }\n+pass() { echo \"PASS: $*\"; exit 0; }\n+\n+[ \"$(id -u)\" -eq 0 ] || skip \"must run as root\"\n+[ -r \"$KMEMLEAK\" ] || skip \"no kmemleak debugfs (CONFIG_DEBUG_KMEMLEAK)\"\n+[ -w \"$PARAM\" ] || skip \"min_unref_scans module parameter not present\"\n+modinfo \"$MODULE\" \u003e/dev/null 2\u003e\u00261 ||\n+\tskip \"$MODULE not built (CONFIG_SAMPLE_KMEMLEAK)\"\n+\n+# kmemleak can be present but disabled at runtime (kmemleak=off boot arg,\n+# or it self-disabled after an internal error); a \"scan\" then returns\n+# EPERM. Probe once and skip if so.\n+echo scan \u003e \"$KMEMLEAK\" 2\u003e/dev/null ||\n+\tskip \"kmemleak is disabled (check dmesg or kmemleak= boot arg)\"\n+\n+prev=$(cat \"$PARAM\")\n+# shellcheck disable=SC2317  # invoked indirectly via trap\n+cleanup() {\n+\techo \"$prev\" \u003e \"$PARAM\" 2\u003e/dev/null\t\t# restore the parameter\n+\techo scan=on \u003e \"$KMEMLEAK\" 2\u003e/dev/null\t\t# re-enable auto scan\n+\trmmod \"$MODULE\" 2\u003e/dev/null\n+\techo clear \u003e \"$KMEMLEAK\" 2\u003e/dev/null\n+}\n+trap cleanup EXIT\n+\n+# Stop the automatic scan thread: only our manual scans should advance an\n+# object's consecutive-unreferenced run. An auto scan landing between two\n+# manual scans would change the result and make the test flaky.\n+echo scan=off \u003e \"$KMEMLEAK\" 2\u003e/dev/null\n+\n+# Create a fresh, aged set of orphan objects from the helper module's init\n+# path (its kmalloc/vmalloc/percpu allocations are dropped right away).\n+# Pre-existing reported leaks are greyed first (\"clear\") so only our\n+# orphans are counted. The module is left loaded on purpose: once it is\n+# unloaded its symbols are gone, so the orphan backtraces no longer resolve\n+# to [kmemleak_test] and could not be matched below.\n+gen_orphans() {\n+\trmmod \"$MODULE\" 2\u003e/dev/null\n+\techo clear \u003e \"$KMEMLEAK\"\n+\tmodprobe \"$MODULE\" || skip \"failed to load $MODULE\"\n+\tsleep \"$AGE\"\n+}\n+\n+scan() { echo scan \u003e \"$KMEMLEAK\"; }\n+\n+# Number of helper-module orphans currently reported by kmemleak. Matching\n+# the module's own backtrace ([kmemleak_test]) keeps the count immune to\n+# unrelated leaks on the running system. kmemleak only lists an object here\n+# once it has been reported, so this reflects the confirmation gating.\n+count_orphans() {\n+\tc=$(grep -c '\\[kmemleak_test\\]' \"$KMEMLEAK\" 2\u003e/dev/null)\n+\techo \"${c:-0}\"\n+}\n+\n+# 0) the parameter reads back what was written.\n+echo 3 \u003e \"$PARAM\"\n+[ \"$(cat \"$PARAM\")\" = \"3\" ] || fail \"min_unref_scans did not read back as 3\"\n+\n+# 1) min_unref_scans=1 (default): orphans reported on the first scan. This\n+#    also establishes that the helper produces detectable orphans here.\n+echo 1 \u003e \"$PARAM\"\n+gen_orphans\n+scan\n+first=$(count_orphans)\n+[ \"$first\" -gt 0 ] ||\n+\tskip \"$MODULE produced no detectable orphans (cannot test min_unref_scans)\"\n+\n+# 2) min_unref_scans=2: nothing reported after the first scan, reported\n+#    after the second. The first-scan-zero check is the core regression.\n+echo 2 \u003e \"$PARAM\"\n+gen_orphans\n+scan; s1=$(count_orphans)\n+scan; s2=$(count_orphans)\n+[ \"$s1\" -eq 0 ] || fail \"min_unref_scans=2: $s1 orphan(s) reported after the 1st scan (must be 0)\"\n+[ \"$s2\" -gt 0 ] || fail \"min_unref_scans=2: no report on the 2nd scan (false negative)\"\n+\n+pass \"min_unref_scans=1 immediate; =2 gated to 2nd scan (counts $first/$s1/$s2); param read-back ok\"\n"
}

gemini-3.1-pro-preview

null

{
  "EnableConfigs": [
    "DEBUG_KMEMLEAK"
  ],
  "FocusSymbols": [
    "kmemleak_scan"
  ],
  "Reasoning": "The patch introduces functional changes to the kmemleak scanning logic by adding a new module parameter `min_unref_scans` and modifying `kmemleak_scan` to require a minimum number of consecutive unreferenced scans before reporting an object. This modifies the core state machine of the leak detector.",
  "WorthFuzzing": true
}

You are an expert Linux kernel maintainer.
Your job is to review a provided patch series and determine
if it makes functional changes to the kernel that should be fuzzed.

IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in
your workspace. Do NOT rely on your internal knowledge of the kernel. You must actively
use your code access tools to examine the actual source code and confirm any assumptions.

Return WorthFuzzing=false if the patch only contains:
- Modifications to Documentation/, Kconfig files, or code comments.
- Purely decorative changes, such as logging (e.g., pr_err, printk) or tracepoints.
- Changes to numeric constants or macros that do not functionally alter execution flow.
- Code paths that are impossible to reach in virtualized environments like GCE or QEMU,
even when utilizing software-emulated hardware (e.g., usb gadget, mac80211_hwsim).

If it modifies reachable core kernel logic, drivers, or architectures, use your code search
tools to verify the code can be executed, then return WorthFuzzing=true.

When returning WorthFuzzing=true, you MUST ALSO:
1. Extract any specific kernel functions that should be heavily fuzzed into FocusSymbols.
   Avoid listing generic hot-path functions to prevent skewed test distributions.
2. Identify any specific CONFIG_ options required to properly test this new/modified feature.
   Go and look into the Kconfig files and check for ifdefs around the code, do not make assumptions.
   Do not list too generic configs (we already have them enabled). Only list those that
   specifically cover the modified code. List them in the EnableConfigs output array,
   and DO NOT add a 'CONFIG_' prefix (e.g., return "NET_IPV4" instead of "CONFIG_NET_IPV4").
Prefer calling several tools at the same time to save round-trips.


Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.

For your convenience, here is the diff of the changes:
commit bd7f4362253e7b5bd9348f17d8a8b580701c84ec
Author: syz-cluster <triage@syzkaller.com>
Date:   Fri Jun 26 22:42:07 2026 +0000

    syz-cluster: applied patch under review

diff --git a/Documentation/dev-tools/kmemleak.rst b/Documentation/dev-tools/kmemleak.rst
index 7d784e03f3f9d5..a8a83bc69ceb88 100644
--- a/Documentation/dev-tools/kmemleak.rst
+++ b/Documentation/dev-tools/kmemleak.rst
@@ -198,6 +198,14 @@ systems, because of pointers temporarily stored in CPU registers or
 stacks. Kmemleak defines MSECS_MIN_AGE (defaulting to 1000) representing
 the minimum age of an object to be reported as a memory leak.
 
+The ``min_unref_scans`` module parameter (default 1) requires an object to
+be seen unreferenced in that many consecutive scans before it is reported.
+Keeping it at 1 preserves the historical behaviour; higher values filter
+the transient false positives described above, at the cost of delaying
+genuine reports by up to that many scans. It can be set at boot with
+``kmemleak.min_unref_scans=<n>`` or at run-time via
+``/sys/module/kmemleak/parameters/min_unref_scans``.
+
 Limitations and Drawbacks
 -------------------------
 
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 7c7ba17ce7af00..5b14ccb36f95ba 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -151,6 +151,8 @@ struct kmemleak_object {
 	int min_count;
 	/* the total number of pointers found pointing to this object */
 	int count;
+	/* consecutive scans the object has been seen unreferenced */
+	unsigned int unref_scans;
 	/* checksum for detecting modified objects */
 	u32 checksum;
 	depot_stack_handle_t trace_handle;
@@ -232,6 +234,9 @@ static unsigned long max_percpu_addr;
 static struct task_struct *scan_thread;
 /* used to avoid reporting of recently allocated objects */
 static unsigned long jiffies_min_age;
+/* consecutive scans an object must stay unreferenced before reporting */
+static unsigned int min_unref_scans = 1;
+module_param(min_unref_scans, uint, 0644);
 static unsigned long jiffies_last_scan;
 /* delay between automatic memory scannings */
 static unsigned long jiffies_scan_wait;
@@ -687,6 +692,7 @@ static struct kmemleak_object *__alloc_object(gfp_t gfp)
 	atomic_set(&object->use_count, 1);
 	object->excess_ref = 0;
 	object->count = 0;			/* white color initially */
+	object->unref_scans = 0;
 	object->checksum = 0;
 	object->del_state = 0;
 
@@ -1833,6 +1839,9 @@ static void kmemleak_scan(void)
 				__paint_it(object, KMEMLEAK_BLACK);
 		}
 
+		/* referenced last scan: restart the unreferenced run */
+		if (!color_white(object))
+			object->unref_scans = 0;
 		/* reset the reference count (whiten the object) */
 		object->count = 0;
 		if (color_gray(object) && get_object(object))
@@ -1968,8 +1977,9 @@ static void kmemleak_scan(void)
 		raw_spin_lock_irq(&object->lock);
 		trace_handle = 0;
 		dedup_print = false;
-		if (unreferenced_object(object) &&
-		    !(object->flags & OBJECT_REPORTED)) {
+		if (!(object->flags & OBJECT_REPORTED) &&
+		    unreferenced_object(object) &&
+		    ++object->unref_scans >= min_unref_scans) {
 			object->flags |= OBJECT_REPORTED;
 			if (kmemleak_verbose) {
 				trace_handle = object->trace_handle;
diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
index e6df968f0971c8..84026b62a1ae5e 100644
--- a/tools/testing/selftests/mm/Makefile
+++ b/tools/testing/selftests/mm/Makefile
@@ -150,6 +150,7 @@ 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 00000000000000..34ab64bc6948f8
--- /dev/null
+++ b/tools/testing/selftests/mm/ksft_kmemleak_confirm.sh
@@ -0,0 +1,111 @@
+#!/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:
+#   - min_unref_scans=1 reports them on the first scan,
+#   - min_unref_scans=2 reports nothing on the first scan but does on the
+#     second,
+#   - the parameter reads back what was written.
+#
+# The "nothing on the first scan" check is the core regression test: with
+# min_unref_scans=2 no object can be reported in fewer than two scans. 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>
+
+ksft_skip=4
+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
+
+skip() { echo "SKIP: $*"; exit $ksft_skip; }
+fail() { echo "FAIL: $*"; exit 1; }
+pass() { echo "PASS: $*"; exit 0; }
+
+[ "$(id -u)" -eq 0 ] || skip "must run as root"
+[ -r "$KMEMLEAK" ] || skip "no kmemleak debugfs (CONFIG_DEBUG_KMEMLEAK)"
+[ -w "$PARAM" ] || skip "min_unref_scans module parameter not present"
+modinfo "$MODULE" >/dev/null 2>&1 ||
+	skip "$MODULE not built (CONFIG_SAMPLE_KMEMLEAK)"
+
+# 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 > "$KMEMLEAK" 2>/dev/null ||
+	skip "kmemleak is disabled (check dmesg or kmemleak= boot arg)"
+
+prev=$(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" || skip "failed to load $MODULE"
+	sleep "$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 "$PARAM")" = "3" ] || fail "min_unref_scans did not read back as 3"
+
+# 1) min_unref_scans=1 (default): orphans reported on the first scan. This
+#    also establishes that the helper produces detectable orphans here.
+echo 1 > "$PARAM"
+gen_orphans
+scan
+first=$(count_orphans)
+[ "$first" -gt 0 ] ||
+	skip "$MODULE produced no detectable orphans (cannot test min_unref_scans)"
+
+# 2) min_unref_scans=2: nothing reported after the first scan, reported
+#    after the second. The first-scan-zero check is the core regression.
+echo 2 > "$PARAM"
+gen_orphans
+scan; s1=$(count_orphans)
+scan; s2=$(count_orphans)
+[ "$s1" -eq 0 ] || fail "min_unref_scans=2: $s1 orphan(s) reported after the 1st scan (must be 0)"
+[ "$s2" -gt 0 ] || fail "min_unref_scans=2: no report on the 2nd scan (false negative)"
+
+pass "min_unref_scans=1 immediate; =2 gated to 2nd scan (counts $first/$s1/$s2); param read-back ok"

gemini-3.1-pro-preview

null

null

							input: 4592
							output: 34
							thoughts: 654
						

**Kmemleak Patch Fuzzing Assessment**

Okay, so I've got this patch that tweaks `mm/kmemleak.c` – adds a `min_unref_scans` module parameter, and a selftest, `ksft_kmemleak_confirm.sh`. It seems to add a new `unref_scans` field in the `kmemleak_object` structure and modifies `kmemleak_scan()` to use it, only reporting an object after a certain number of unreferenced scans. My immediate thought is to decide if this needs focused fuzzing.

Kmemleak is a memory leak detector, a debugging tool. It's not a direct consumer of untrusted input in the same way, say, a network stack driver is. It's purpose is to find leaks, but it does this by scanning existing memory. But hold on, the patch modifies the tool itself! Can a fuzzer *trigger* the new code paths? Absolutely, by leaking memory or interacting with kmemleak via debugfs or module parameters, like the one added in the patch.

The general practice is that tools like this are *enabled* during fuzzing to catch bugs in other kernel subsystems, but not primarily fuzzed themselves. But this is *different* - the patch *changes* how kmemleak works. It's functional, adding a new control and changing the reporting logic.

The crucial question is whether fuzzing *kmemleak itself* is worthwhile. I'm leaning toward "no" as a primary target. Diagnostic tools aren't usually where we focus our fuzzing efforts. However, syzkaller *does* have descriptions for debugfs, and I'd need to consider those.

Now, the prompt reminds me of the criteria for *not* fuzzing: docs, comments, logging, constants, unreachable code in virtualized environments. This patch clearly modifies *actual kernel logic* within the `mm/` directory – it's not just documentation. It's functional, altering how kmemleak operates. `kmemleak_scan` is modified, and the change has a functional impact on how leaks are reported. I should look at `mm/kmemleak.c` more closely and consider other functions as well. `__alloc_object` has also been changed.

So, according to my internal assessment, and in relation to the guidelines, I think it's time to run some verification tools and confirm this.

{
  "Expression": "min_unref_scans",
  "PathPrefix": "mm/kmemleak.c"
}

{
  "Output": "mm/kmemleak.c=236=static unsigned long jiffies_min_age;\nmm/kmemleak.c-237-/* consecutive scans an object must stay unreferenced before reporting */\nmm/kmemleak.c:238:static unsigned int min_unref_scans = 1;\nmm/kmemleak.c:239:module_param(min_unref_scans, uint, 0644);\nmm/kmemleak.c-240-static unsigned long jiffies_last_scan;\n--\nmm/kmemleak.c=1806=static void kmemleak_scan(void)\n--\nmm/kmemleak.c-1981-\t\t    unreferenced_object(object) \u0026\u0026\nmm/kmemleak.c:1982:\t\t    ++object-\u003eunref_scans \u003e= min_unref_scans) {\nmm/kmemleak.c-1983-\t\t\tobject-\u003eflags |= OBJECT_REPORTED;\n"
}

gemini-3.1-pro-preview

null

null

							input: 6055
							output: 33
							thoughts: 196
						

**Fuzzing the kmemleak Delay Counter**

Okay, so this patch is touching `kmemleak_scan` and `__alloc_object`.  `kmemleak_scan` is either a thread or triggered via debugfs, which sounds potentially interesting for fuzzing.  `__alloc_object`, however, is called every single time kmemleak tracks an allocation.  That's a hot-path function; it's practically going to be hit all the time if kmemleak is enabled, and the instructions are to avoid hot-path functions.

So, is this even worth the effort? The change itself is pretty straightforward – it’s just a counter to delay leak reporting.  Fuzzing *specifically* the counter and its interaction with these functions might not uncover anything earth-shattering.  Still, it *is* a functional change, and functional changes are valid targets. If I decide it *is* worth fuzzing, I'll need to specify `FocusSymbols` and `EnableConfigs`.

Given that `__alloc_object` is a hot-path function, I'm going to lean towards just fuzzing `kmemleak_scan`. It's the only one that seems practical to put in focus.

Before I commit to anything, I should double check the Kconfig settings related to kmemleak to make sure I understand the relevant build configurations.

no matches

{
  "Expression": "config DEBUG_KMEMLEAK",
  "PathPrefix": "lib/Kconfig.debug"
}

{
  "error": "no matches"
}

gemini-3.1-pro-preview

null

null

							input: 6591
							output: 27
							thoughts: 14
						

Okay, here's my summary, presented as a stream of thought:

**Tracing Down DEBUG_KMEMLEAK**

Alright, time to get to the bottom of this. I need to find the definition of `DEBUG_KMEMLEAK`. This is usually the starting point for understanding how a feature or debugging tool works within a kernel or system. Knowing where it's defined will give me clues about its scope, dependencies, and intended purpose. From there, I can likely trace its usage, understand the conditions under which it's active, and eventually piece together the entire implementation. Let's see if I can use some grep or similar tooling to track down the header files or configuration files where this macro is declared. Knowing the exact definition is key.

{
  "Expression": "config DEBUG_KMEMLEAK",
  "PathPrefix": ""
}

{
  "Output": "mm/Kconfig.debug=237=config HAVE_DEBUG_KMEMLEAK\n--\nmm/Kconfig.debug-239-\nmm/Kconfig.debug:240:config DEBUG_KMEMLEAK\nmm/Kconfig.debug-241-\tbool \"Kernel memory leak detector\"\n--\nmm/Kconfig.debug-264-\nmm/Kconfig.debug:265:config DEBUG_KMEMLEAK_MEM_POOL_SIZE\nmm/Kconfig.debug-266-\tint \"Kmemleak memory pool size\"\n--\nmm/Kconfig.debug-277-\nmm/Kconfig.debug:278:config DEBUG_KMEMLEAK_DEFAULT_OFF\nmm/Kconfig.debug-279-\tbool \"Default kmemleak to off\"\n--\nmm/Kconfig.debug-284-\nmm/Kconfig.debug:285:config DEBUG_KMEMLEAK_AUTO_SCAN\nmm/Kconfig.debug-286-\tbool \"Enable kmemleak auto scan thread on boot up\"\n--\nmm/Kconfig.debug-299-\nmm/Kconfig.debug:300:config DEBUG_KMEMLEAK_VERBOSE\nmm/Kconfig.debug-301-\tbool \"Default kmemleak to verbose mode\"\n"
}

gemini-3.1-pro-preview

null

null

							input: 7117
							output: 36
							thoughts: 250
						

**Fuzzing the `DEBUG_KMEMLEAK` Config Change**

Okay, so this config change enables `DEBUG_KMEMLEAK`. The question is, is fuzzing it worth the effort? From a functional perspective, it modifies `kmemleak_scan` to require a certain number of consecutive unreferenced scans (`min_unref_scans`) before reporting a leak. It's essentially a straightforward state machine, a counter that resets upon referencing and increments if unreferenced.

While a functional change, it's specific to a debugging tool. Syzkaller often has `DEBUG_KMEMLEAK` enabled by default for detecting leaks in *other* code. The goal of fuzzing this patch is to specifically target the new logic within `kmemleak_scan` itself, looking for bugs like integer overflows or race conditions.

Now, looking at the code, `object->unref_scans` is an `unsigned int`, which is incremented within `kmemleak_scan` under a `raw_spin_lock_irq(&object->lock)`. But wait, I just noticed something. The variable `object->unref_scans` is initialized to zero within the same function and *without* the lock. This bears looking into. I should probably check `mm/kmemleak.c` around line 1839. That could be a potential race condition.

{
  "File": "mm/kmemleak.c",
  "FirstLine": 1830,
  "LineCount": 30
}

{
  "Contents": "1830:\t#endif\n1831:\t\n1832:\t\t\t/* ignore objects outside lowmem (paint them black) */\n1833:\t\t\tif ((object-\u003eflags \u0026 OBJECT_PHYS) \u0026\u0026\n1834:\t\t\t   !(object-\u003eflags \u0026 OBJECT_NO_SCAN)) {\n1835:\t\t\t\tunsigned long phys = object-\u003epointer;\n1836:\t\n1837:\t\t\t\tif (PHYS_PFN(phys) \u003c min_low_pfn ||\n1838:\t\t\t\t    PHYS_PFN(phys + object-\u003esize) \u003e max_low_pfn)\n1839:\t\t\t\t\t__paint_it(object, KMEMLEAK_BLACK);\n1840:\t\t\t}\n1841:\t\n1842:\t\t\t/* referenced last scan: restart the unreferenced run */\n1843:\t\t\tif (!color_white(object))\n1844:\t\t\t\tobject-\u003eunref_scans = 0;\n1845:\t\t\t/* reset the reference count (whiten the object) */\n1846:\t\t\tobject-\u003ecount = 0;\n1847:\t\t\tif (color_gray(object) \u0026\u0026 get_object(object))\n1848:\t\t\t\tlist_add_tail(\u0026object-\u003egray_list, \u0026gray_list);\n1849:\t\n1850:\t\t\traw_spin_unlock_irq(\u0026object-\u003elock);\n1851:\t\n1852:\t\t\tif (need_resched())\n1853:\t\t\t\tkmemleak_cond_resched(object);\n1854:\t\t}\n1855:\t\trcu_read_unlock();\n1856:\t\n1857:\t#ifdef CONFIG_SMP\n1858:\t\t/* per-cpu sections scanning */\n1859:\t\tfor_each_possible_cpu(i)\n"
}

gemini-3.1-pro-preview

null

null

							input: 8164
							output: 31
							thoughts: 95
						

**Fuzzing KMEMLEAK: A Targeted Approach**

Okay, so I've pinpointed the relevant code segment. The crucial locking operation, the raw spin lock, is happening within the `raw_spin_lock_irq(&object->lock)` block. Relief! The corresponding release is handled further down, at line 1850. Looks safe from a basic lock/unlock perspective.

Now, the important question: is this fuzzable? Absolutely. This is a functional change within the kernel, making it a prime target. Time to make sure I'm going to be as efficient as possible. I'll need to focus my efforts on `kmemleak_scan`.

Let's also make sure I've got the necessary infrastructure in place: `DEBUG_KMEMLEAK` will be my friend.

Just to be thorough, I'm going to quickly check for any other modified functions in the patch. Gotta ensure I haven't missed anything crucial that could influence the fuzzing strategy.

{
  "Expression": "__alloc_object",
  "PathPrefix": "mm/kmemleak.c"
}

{
  "Output": "mm/kmemleak.c=658=static noinline depot_stack_handle_t set_track_prepare(void)\n--\nmm/kmemleak.c-676-\nmm/kmemleak.c:677:static struct kmemleak_object *__alloc_object(gfp_t gfp)\nmm/kmemleak.c-678-{\n--\nmm/kmemleak.c=789=static void __create_object(unsigned long ptr, size_t size,\n--\nmm/kmemleak.c-795-\nmm/kmemleak.c:796:\tobject = __alloc_object(gfp);\nmm/kmemleak.c-797-\tif (!object)\n--\nmm/kmemleak.c=871=static void delete_object_part(unsigned long ptr, size_t size,\n--\nmm/kmemleak.c-876-\nmm/kmemleak.c:877:\tobject_l = __alloc_object(GFP_KERNEL);\nmm/kmemleak.c-878-\tif (!object_l)\n--\nmm/kmemleak.c-880-\nmm/kmemleak.c:881:\tobject_r = __alloc_object(GFP_KERNEL);\nmm/kmemleak.c-882-\tif (!object_r)\n"
}

gemini-3.1-pro-preview

null

null

							input: 8853
							output: 108
							thoughts: 279
						

**Analyzing the kmemleak Patch for Fuzzing Potential**

Okay, so this patch is touching `kmemleak`, which is interesting from a fuzzing perspective. The key here is the hot-path function `__alloc_object` and `kmemleak_scan`. We need to avoid `__alloc_object` due to its high-frequency use. The main scanning logic seems to be concentrated in `kmemleak_scan`, which is where the new `unref_scans` field comes into play.

Let's quickly check the relevant configurations. The big one seems to be `CONFIG_DEBUG_KMEMLEAK`, of course. Hmm, `min_unref_scans` is a module parameter – that could be useful to manipulate. Other than those, I don't see any other modified functions. The patch is primarily focused on `__alloc_object` and `kmemleak_scan`, which is good news for focusing our fuzzing efforts.

Now, is `kmemleak_scan` reachable? Yes, it's called by `kmemleak_scan_thread` and, importantly, through the debugfs write to `/sys/kernel/debug/kmemleak`. And hey, Syzkaller has descriptions for that debugfs interface. Perfect! This means we can trigger the core functionality of `kmemleak_scan` pretty easily.

Given this analysis, I'm confident in saying that this patch presents a valuable fuzzing target. The new logic in `kmemleak` to delay leak reporting and require a minimum number of unreferenced scans *directly* modifies the core scan logic in `kmemleak_scan`. We should definitely be fuzzing this!

Therefore, I'll return WorthFuzzing=true, focus our fuzzing efforts on `kmemleak_scan`, enable `DEBUG_KMEMLEAK`, and the reason is the patch introduces new critical logic in kmemleak.

{
  "EnableConfigs": [
    "DEBUG_KMEMLEAK"
  ],
  "FocusSymbols": [
    "kmemleak_scan"
  ],
  "Reasoning": "The patch introduces functional changes to the kmemleak scanning logic by adding a new module parameter `min_unref_scans` and modifying `kmemleak_scan` to require a minimum number of consecutive unreferenced scans before reporting an object. This modifies the core state machine of the leak detector.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "DEBUG_KMEMLEAK"
  ],
  "FocusSymbols": [
    "kmemleak_scan"
  ],
  "Reasoning": "The patch introduces functional changes to the kmemleak scanning logic by adding a new module parameter `min_unref_scans` and modifying `kmemleak_scan` to require a minimum number of consecutive unreferenced scans before reporting an object. This modifies the core state machine of the leak detector.",
  "WorthFuzzing": true
}