* [PATCH v2] sched_ext/selftests: Fix bpf_link leak on assertion failure
2026-03-17 17:44 [PATCH] sched_ext/selftests: Fix bpf_link leak on assertion failure David Carlier
2026-03-17 18:09 ` Tejun Heo
@ 2026-03-17 18:28 ` David Carlier
1 sibling, 0 replies; 3+ messages in thread
From: David Carlier @ 2026-03-17 18:28 UTC (permalink / raw)
To: Tejun Heo, David Vernet, Andrea Righi; +Cc: linux-kernel, David Carlier
The SCX_EQ/SCX_ASSERT/SCX_FAIL_IF macros expand to return
SCX_TEST_FAIL on failure. When an assertion fires after
bpf_map__attach_struct_ops() but before bpf_link__destroy(), the
link leaks. Since the test runner is a single process, the leaked
link keeps the BPF scheduler attached, causing subsequent tests to
fail to attach their own scheduler -- cascading test failures from
a single bug.
Fix by introducing an __autolink cleanup attribute, as suggested
by Tejun, that auto-destroys the bpf_link when the variable goes
out of scope, covering both normal and early return paths. This
avoids the need to reorder bpf_link__destroy() before assertions,
which would break tests that assert SCX_EXIT_NONE (where the
scheduler is still running and bpf_link__destroy() would trigger
unregistration, changing uei.kind to SCX_EXIT_UNREG).
---
tools/testing/selftests/sched_ext/allowed_cpus.c | 3 +--
tools/testing/selftests/sched_ext/ddsp_bogus_dsq_fail.c | 3 +--
tools/testing/selftests/sched_ext/ddsp_vtimelocal_fail.c | 3 +--
tools/testing/selftests/sched_ext/dequeue.c | 3 ++-
tools/testing/selftests/sched_ext/enq_last_no_enq_fails.c | 4 +---
tools/testing/selftests/sched_ext/enq_select_cpu.c | 3 +--
tools/testing/selftests/sched_ext/exit.c | 3 +--
tools/testing/selftests/sched_ext/hotplug.c | 6 ++----
tools/testing/selftests/sched_ext/numa.c | 3 +--
tools/testing/selftests/sched_ext/peek_dsq.c | 8 +-------
tools/testing/selftests/sched_ext/prog_run.c | 3 +--
tools/testing/selftests/sched_ext/rt_stall.c | 6 ++----
tools/testing/selftests/sched_ext/scx_test.h | 8 ++++++++
tools/testing/selftests/sched_ext/select_cpu_dfl.c | 4 +---
.../selftests/sched_ext/select_cpu_dfl_nodispatch.c | 4 +---
tools/testing/selftests/sched_ext/select_cpu_dispatch.c | 4 +---
.../selftests/sched_ext/select_cpu_dispatch_bad_dsq.c | 3 +--
.../selftests/sched_ext/select_cpu_dispatch_dbl_dsp.c | 3 +--
tools/testing/selftests/sched_ext/select_cpu_vtime.c | 4 +---
19 files changed, 29 insertions(+), 49 deletions(-)
diff --git a/tools/testing/selftests/sched_ext/allowed_cpus.c b/tools/testing/selftests/sched_ext/allowed_cpus.c
index 093f285ab4ba..33fe9cb77159 100644
--- a/tools/testing/selftests/sched_ext/allowed_cpus.c
+++ b/tools/testing/selftests/sched_ext/allowed_cpus.c
@@ -50,7 +50,7 @@ static int test_select_cpu_from_user(const struct allowed_cpus *skel)
static enum scx_test_status run(void *ctx)
{
struct allowed_cpus *skel = ctx;
- struct bpf_link *link;
+ struct bpf_link *link __autolink = NULL;
link = bpf_map__attach_struct_ops(skel->maps.allowed_cpus_ops);
SCX_FAIL_IF(!link, "Failed to attach scheduler");
@@ -62,7 +62,6 @@ static enum scx_test_status run(void *ctx)
sleep(1);
SCX_EQ(skel->data->uei.kind, EXIT_KIND(SCX_EXIT_NONE));
- bpf_link__destroy(link);
return SCX_TEST_PASS;
}
diff --git a/tools/testing/selftests/sched_ext/ddsp_bogus_dsq_fail.c b/tools/testing/selftests/sched_ext/ddsp_bogus_dsq_fail.c
index b6d13496b24e..62ca2d57eb6e 100644
--- a/tools/testing/selftests/sched_ext/ddsp_bogus_dsq_fail.c
+++ b/tools/testing/selftests/sched_ext/ddsp_bogus_dsq_fail.c
@@ -28,7 +28,7 @@ static enum scx_test_status setup(void **ctx)
static enum scx_test_status run(void *ctx)
{
struct ddsp_bogus_dsq_fail *skel = ctx;
- struct bpf_link *link;
+ struct bpf_link *link __autolink = NULL;
link = bpf_map__attach_struct_ops(skel->maps.ddsp_bogus_dsq_fail_ops);
SCX_FAIL_IF(!link, "Failed to attach struct_ops");
@@ -36,7 +36,6 @@ static enum scx_test_status run(void *ctx)
sleep(1);
SCX_EQ(skel->data->uei.kind, EXIT_KIND(SCX_EXIT_ERROR));
- bpf_link__destroy(link);
return SCX_TEST_PASS;
}
diff --git a/tools/testing/selftests/sched_ext/ddsp_vtimelocal_fail.c b/tools/testing/selftests/sched_ext/ddsp_vtimelocal_fail.c
index af9ce4ee8baa..f66056450a81 100644
--- a/tools/testing/selftests/sched_ext/ddsp_vtimelocal_fail.c
+++ b/tools/testing/selftests/sched_ext/ddsp_vtimelocal_fail.c
@@ -27,7 +27,7 @@ static enum scx_test_status setup(void **ctx)
static enum scx_test_status run(void *ctx)
{
struct ddsp_vtimelocal_fail *skel = ctx;
- struct bpf_link *link;
+ struct bpf_link *link __autolink = NULL;
link = bpf_map__attach_struct_ops(skel->maps.ddsp_vtimelocal_fail_ops);
SCX_FAIL_IF(!link, "Failed to attach struct_ops");
@@ -35,7 +35,6 @@ static enum scx_test_status run(void *ctx)
sleep(1);
SCX_EQ(skel->data->uei.kind, EXIT_KIND(SCX_EXIT_ERROR));
- bpf_link__destroy(link);
return SCX_TEST_PASS;
}
diff --git a/tools/testing/selftests/sched_ext/dequeue.c b/tools/testing/selftests/sched_ext/dequeue.c
index 4e93262703ca..b7dec70213c7 100644
--- a/tools/testing/selftests/sched_ext/dequeue.c
+++ b/tools/testing/selftests/sched_ext/dequeue.c
@@ -80,7 +80,7 @@ static void *affinity_hammer_fn(void *arg)
static enum scx_test_status run_scenario(struct dequeue *skel, u32 scenario,
const char *scenario_name)
{
- struct bpf_link *link;
+ struct bpf_link *link __autolink = NULL;
pid_t pids[NUM_WORKERS];
pthread_t hammer;
@@ -132,6 +132,7 @@ static enum scx_test_status run_scenario(struct dequeue *skel, u32 scenario,
}
bpf_link__destroy(link);
+ link = NULL;
SCX_EQ(skel->data->uei.kind, EXIT_KIND(SCX_EXIT_UNREG));
diff --git a/tools/testing/selftests/sched_ext/enq_last_no_enq_fails.c b/tools/testing/selftests/sched_ext/enq_last_no_enq_fails.c
index d3387ae03679..22a8312223f6 100644
--- a/tools/testing/selftests/sched_ext/enq_last_no_enq_fails.c
+++ b/tools/testing/selftests/sched_ext/enq_last_no_enq_fails.c
@@ -28,7 +28,7 @@ static enum scx_test_status setup(void **ctx)
static enum scx_test_status run(void *ctx)
{
struct enq_last_no_enq_fails *skel = ctx;
- struct bpf_link *link;
+ struct bpf_link *link __autolink = NULL;
link = bpf_map__attach_struct_ops(skel->maps.enq_last_no_enq_fails_ops);
if (!link) {
@@ -40,8 +40,6 @@ static enum scx_test_status run(void *ctx)
return SCX_TEST_FAIL;
}
- bpf_link__destroy(link);
-
return SCX_TEST_PASS;
}
diff --git a/tools/testing/selftests/sched_ext/enq_select_cpu.c b/tools/testing/selftests/sched_ext/enq_select_cpu.c
index 340c6f8b86da..5d220ee0442b 100644
--- a/tools/testing/selftests/sched_ext/enq_select_cpu.c
+++ b/tools/testing/selftests/sched_ext/enq_select_cpu.c
@@ -52,7 +52,7 @@ static int test_select_cpu_from_user(const struct enq_select_cpu *skel)
static enum scx_test_status run(void *ctx)
{
struct enq_select_cpu *skel = ctx;
- struct bpf_link *link;
+ struct bpf_link *link __autolink = NULL;
link = bpf_map__attach_struct_ops(skel->maps.enq_select_cpu_ops);
if (!link) {
@@ -66,7 +66,6 @@ static enum scx_test_status run(void *ctx)
sleep(1);
SCX_EQ(skel->data->uei.kind, EXIT_KIND(SCX_EXIT_NONE));
- bpf_link__destroy(link);
return SCX_TEST_PASS;
}
diff --git a/tools/testing/selftests/sched_ext/exit.c b/tools/testing/selftests/sched_ext/exit.c
index b987611789d1..9c0e528bcc11 100644
--- a/tools/testing/selftests/sched_ext/exit.c
+++ b/tools/testing/selftests/sched_ext/exit.c
@@ -19,7 +19,7 @@ static enum scx_test_status run(void *ctx)
for (tc = 0; tc < NUM_EXITS; tc++) {
struct exit *skel;
- struct bpf_link *link;
+ struct bpf_link *link __autolink = NULL;
char buf[16];
/*
@@ -49,7 +49,6 @@ static enum scx_test_status run(void *ctx)
SCX_EQ(skel->data->uei.exit_code, tc);
sprintf(buf, "%d", tc);
SCX_ASSERT(!strcmp(skel->data->uei.msg, buf));
- bpf_link__destroy(link);
exit__destroy(skel);
}
diff --git a/tools/testing/selftests/sched_ext/hotplug.c b/tools/testing/selftests/sched_ext/hotplug.c
index 0cfbb111a2d0..c1ff513b9579 100644
--- a/tools/testing/selftests/sched_ext/hotplug.c
+++ b/tools/testing/selftests/sched_ext/hotplug.c
@@ -43,7 +43,7 @@ static enum scx_test_status setup(void **ctx)
static enum scx_test_status test_hotplug(bool onlining, bool cbs_defined)
{
struct hotplug *skel;
- struct bpf_link *link;
+ struct bpf_link *link __autolink = NULL;
long kind, code;
SCX_ASSERT(is_cpu_online());
@@ -90,7 +90,6 @@ static enum scx_test_status test_hotplug(bool onlining, bool cbs_defined)
if (!onlining)
toggle_online_status(1);
- bpf_link__destroy(link);
hotplug__destroy(skel);
return SCX_TEST_PASS;
@@ -99,7 +98,7 @@ static enum scx_test_status test_hotplug(bool onlining, bool cbs_defined)
static enum scx_test_status test_hotplug_attach(void)
{
struct hotplug *skel;
- struct bpf_link *link;
+ struct bpf_link *link __autolink = NULL;
enum scx_test_status status = SCX_TEST_PASS;
long kind, code;
@@ -130,7 +129,6 @@ static enum scx_test_status test_hotplug_attach(void)
SCX_EQ(skel->data->uei.kind, kind);
SCX_EQ(UEI_REPORT(skel, uei), code);
- bpf_link__destroy(link);
hotplug__destroy(skel);
return status;
diff --git a/tools/testing/selftests/sched_ext/numa.c b/tools/testing/selftests/sched_ext/numa.c
index b060c3b65c82..fe2dab1c73ae 100644
--- a/tools/testing/selftests/sched_ext/numa.c
+++ b/tools/testing/selftests/sched_ext/numa.c
@@ -28,7 +28,7 @@ static enum scx_test_status setup(void **ctx)
static enum scx_test_status run(void *ctx)
{
struct numa *skel = ctx;
- struct bpf_link *link;
+ struct bpf_link *link __autolink = NULL;
link = bpf_map__attach_struct_ops(skel->maps.numa_ops);
SCX_FAIL_IF(!link, "Failed to attach scheduler");
@@ -37,7 +37,6 @@ static enum scx_test_status run(void *ctx)
sleep(1);
SCX_EQ(skel->data->uei.kind, EXIT_KIND(SCX_EXIT_NONE));
- bpf_link__destroy(link);
return SCX_TEST_PASS;
}
diff --git a/tools/testing/selftests/sched_ext/peek_dsq.c b/tools/testing/selftests/sched_ext/peek_dsq.c
index a717384a3224..e7fd52ef15f6 100644
--- a/tools/testing/selftests/sched_ext/peek_dsq.c
+++ b/tools/testing/selftests/sched_ext/peek_dsq.c
@@ -84,7 +84,7 @@ static enum scx_test_status run(void *ctx)
/* Enable the scheduler to test DSQ operations */
printf("Enabling scheduler to test DSQ insert operations...\n");
- struct bpf_link *link =
+ struct bpf_link *link __autolink =
bpf_map__attach_struct_ops(skel->maps.peek_dsq_ops);
if (!link) {
@@ -102,7 +102,6 @@ static enum scx_test_status run(void *ctx)
workload_running = false;
for (int j = 0; j < i; j++)
pthread_join(workload_threads[j], NULL);
- bpf_link__destroy(link);
return SCX_TEST_FAIL;
}
}
@@ -120,7 +119,6 @@ static enum scx_test_status run(void *ctx)
workload_running = false;
for (int i = 0; i < NUM_WORKERS; i++)
pthread_join(workload_threads[i], NULL);
- bpf_link__destroy(link);
return SCX_TEST_FAIL;
}
}
@@ -130,7 +128,6 @@ static enum scx_test_status run(void *ctx)
err = pthread_join(workload_threads[i], NULL);
if (err) {
SCX_ERR("Failed to join workload thread %d: %s", i, strerror(err));
- bpf_link__destroy(link);
return SCX_TEST_FAIL;
}
}
@@ -138,9 +135,6 @@ static enum scx_test_status run(void *ctx)
SCX_EQ(skel->data->uei.kind, EXIT_KIND(SCX_EXIT_NONE));
- /* Detach the scheduler */
- bpf_link__destroy(link);
-
printf("Enqueue/dispatch count over %d seconds: %d / %d\n", seconds,
skel->data->enqueue_count, skel->data->dispatch_count);
printf("Debug: ksym_exists=%d\n",
diff --git a/tools/testing/selftests/sched_ext/prog_run.c b/tools/testing/selftests/sched_ext/prog_run.c
index 05974820ca69..342cf000f514 100644
--- a/tools/testing/selftests/sched_ext/prog_run.c
+++ b/tools/testing/selftests/sched_ext/prog_run.c
@@ -28,7 +28,7 @@ static enum scx_test_status setup(void **ctx)
static enum scx_test_status run(void *ctx)
{
struct prog_run *skel = ctx;
- struct bpf_link *link;
+ struct bpf_link *link __autolink = NULL;
int prog_fd, err = 0;
prog_fd = bpf_program__fd(skel->progs.prog_run_syscall);
@@ -56,7 +56,6 @@ static enum scx_test_status run(void *ctx)
SCX_EQ(skel->data->uei.kind, EXIT_KIND(SCX_EXIT_UNREG_BPF));
SCX_EQ(skel->data->uei.exit_code, 0xdeadbeef);
close(prog_fd);
- bpf_link__destroy(link);
return SCX_TEST_PASS;
}
diff --git a/tools/testing/selftests/sched_ext/rt_stall.c b/tools/testing/selftests/sched_ext/rt_stall.c
index 81ea9b4883e5..20534abf3622 100644
--- a/tools/testing/selftests/sched_ext/rt_stall.c
+++ b/tools/testing/selftests/sched_ext/rt_stall.c
@@ -238,7 +238,6 @@ static bool sched_stress_test(bool is_ext)
static enum scx_test_status run(void *ctx)
{
struct rt_stall *skel = ctx;
- struct bpf_link *link = NULL;
bool res;
int i;
@@ -251,6 +250,7 @@ static enum scx_test_status run(void *ctx)
* - ext_server stop -> fair_server stop
*/
for (i = 0; i < 4; i++) {
+ struct bpf_link *link __autolink = NULL;
bool is_ext = i % 2;
if (is_ext) {
@@ -259,10 +259,8 @@ static enum scx_test_status run(void *ctx)
SCX_FAIL_IF(!link, "Failed to attach scheduler");
}
res = sched_stress_test(is_ext);
- if (is_ext) {
+ if (is_ext)
SCX_EQ(skel->data->uei.kind, EXIT_KIND(SCX_EXIT_NONE));
- bpf_link__destroy(link);
- }
if (!res)
ksft_exit_fail();
diff --git a/tools/testing/selftests/sched_ext/scx_test.h b/tools/testing/selftests/sched_ext/scx_test.h
index 90b8d6915bb7..f75b5025c9f1 100644
--- a/tools/testing/selftests/sched_ext/scx_test.h
+++ b/tools/testing/selftests/sched_ext/scx_test.h
@@ -79,6 +79,14 @@ void scx_test_register(struct scx_test *test);
scx_test_register(__test); \
}
+static inline void autolink_destroy(struct bpf_link **linkp)
+{
+ if (*linkp)
+ bpf_link__destroy(*linkp);
+}
+
+#define __autolink __attribute__((cleanup(autolink_destroy)))
+
#define SCX_ERR(__fmt, ...) \
do { \
fprintf(stderr, "ERR: %s:%d\n", __FILE__, __LINE__); \
diff --git a/tools/testing/selftests/sched_ext/select_cpu_dfl.c b/tools/testing/selftests/sched_ext/select_cpu_dfl.c
index 5b6e045e1109..ced1a2ec5417 100644
--- a/tools/testing/selftests/sched_ext/select_cpu_dfl.c
+++ b/tools/testing/selftests/sched_ext/select_cpu_dfl.c
@@ -30,7 +30,7 @@ static enum scx_test_status setup(void **ctx)
static enum scx_test_status run(void *ctx)
{
struct select_cpu_dfl *skel = ctx;
- struct bpf_link *link;
+ struct bpf_link *link __autolink = NULL;
pid_t pids[NUM_CHILDREN];
int i, status;
@@ -52,8 +52,6 @@ static enum scx_test_status run(void *ctx)
SCX_ASSERT(!skel->bss->saw_local);
- bpf_link__destroy(link);
-
return SCX_TEST_PASS;
}
diff --git a/tools/testing/selftests/sched_ext/select_cpu_dfl_nodispatch.c b/tools/testing/selftests/sched_ext/select_cpu_dfl_nodispatch.c
index 9b5d232efb7f..4014a812f85f 100644
--- a/tools/testing/selftests/sched_ext/select_cpu_dfl_nodispatch.c
+++ b/tools/testing/selftests/sched_ext/select_cpu_dfl_nodispatch.c
@@ -30,7 +30,7 @@ static enum scx_test_status setup(void **ctx)
static enum scx_test_status run(void *ctx)
{
struct select_cpu_dfl_nodispatch *skel = ctx;
- struct bpf_link *link;
+ struct bpf_link *link __autolink = NULL;
pid_t pids[NUM_CHILDREN];
int i, status;
@@ -52,8 +52,6 @@ static enum scx_test_status run(void *ctx)
SCX_ASSERT(skel->bss->saw_local);
- bpf_link__destroy(link);
-
return SCX_TEST_PASS;
}
diff --git a/tools/testing/selftests/sched_ext/select_cpu_dispatch.c b/tools/testing/selftests/sched_ext/select_cpu_dispatch.c
index 80283dbc41b7..cecab356f915 100644
--- a/tools/testing/selftests/sched_ext/select_cpu_dispatch.c
+++ b/tools/testing/selftests/sched_ext/select_cpu_dispatch.c
@@ -30,7 +30,7 @@ static enum scx_test_status setup(void **ctx)
static enum scx_test_status run(void *ctx)
{
struct select_cpu_dispatch *skel = ctx;
- struct bpf_link *link;
+ struct bpf_link *link __autolink = NULL;
pid_t pids[NUM_CHILDREN];
int i, status;
@@ -50,8 +50,6 @@ static enum scx_test_status run(void *ctx)
SCX_EQ(status, 0);
}
- bpf_link__destroy(link);
-
return SCX_TEST_PASS;
}
diff --git a/tools/testing/selftests/sched_ext/select_cpu_dispatch_bad_dsq.c b/tools/testing/selftests/sched_ext/select_cpu_dispatch_bad_dsq.c
index 5e72ebbc90a5..f4891e4293d2 100644
--- a/tools/testing/selftests/sched_ext/select_cpu_dispatch_bad_dsq.c
+++ b/tools/testing/selftests/sched_ext/select_cpu_dispatch_bad_dsq.c
@@ -28,7 +28,7 @@ static enum scx_test_status setup(void **ctx)
static enum scx_test_status run(void *ctx)
{
struct select_cpu_dispatch_bad_dsq *skel = ctx;
- struct bpf_link *link;
+ struct bpf_link *link __autolink = NULL;
link = bpf_map__attach_struct_ops(skel->maps.select_cpu_dispatch_bad_dsq_ops);
SCX_FAIL_IF(!link, "Failed to attach scheduler");
@@ -36,7 +36,6 @@ static enum scx_test_status run(void *ctx)
sleep(1);
SCX_EQ(skel->data->uei.kind, EXIT_KIND(SCX_EXIT_ERROR));
- bpf_link__destroy(link);
return SCX_TEST_PASS;
}
diff --git a/tools/testing/selftests/sched_ext/select_cpu_dispatch_dbl_dsp.c b/tools/testing/selftests/sched_ext/select_cpu_dispatch_dbl_dsp.c
index aa85949478bc..c13ccf26cfed 100644
--- a/tools/testing/selftests/sched_ext/select_cpu_dispatch_dbl_dsp.c
+++ b/tools/testing/selftests/sched_ext/select_cpu_dispatch_dbl_dsp.c
@@ -28,7 +28,7 @@ static enum scx_test_status setup(void **ctx)
static enum scx_test_status run(void *ctx)
{
struct select_cpu_dispatch_dbl_dsp *skel = ctx;
- struct bpf_link *link;
+ struct bpf_link *link __autolink = NULL;
link = bpf_map__attach_struct_ops(skel->maps.select_cpu_dispatch_dbl_dsp_ops);
SCX_FAIL_IF(!link, "Failed to attach scheduler");
@@ -36,7 +36,6 @@ static enum scx_test_status run(void *ctx)
sleep(1);
SCX_EQ(skel->data->uei.kind, EXIT_KIND(SCX_EXIT_ERROR));
- bpf_link__destroy(link);
return SCX_TEST_PASS;
}
diff --git a/tools/testing/selftests/sched_ext/select_cpu_vtime.c b/tools/testing/selftests/sched_ext/select_cpu_vtime.c
index 1e9b5c9bfff1..f4edf2861502 100644
--- a/tools/testing/selftests/sched_ext/select_cpu_vtime.c
+++ b/tools/testing/selftests/sched_ext/select_cpu_vtime.c
@@ -28,7 +28,7 @@ static enum scx_test_status setup(void **ctx)
static enum scx_test_status run(void *ctx)
{
struct select_cpu_vtime *skel = ctx;
- struct bpf_link *link;
+ struct bpf_link *link __autolink = NULL;
SCX_ASSERT(!skel->bss->consumed);
@@ -39,8 +39,6 @@ static enum scx_test_status run(void *ctx)
SCX_ASSERT(skel->bss->consumed);
- bpf_link__destroy(link);
-
return SCX_TEST_PASS;
}
--
2.53.0
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