From: Leon Hwang <leon.hwang@linux.dev>
To: Yonghong Song <yonghong.song@linux.dev>, bpf@vger.kernel.org
Cc: ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net,
martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org,
john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me,
haoluo@google.com, jolsa@kernel.org, memxor@gmail.com,
ameryhung@gmail.com, linux-kernel@vger.kernel.org,
kernel-patches-bot@fb.com
Subject: Re: [PATCH bpf-next v4 4/4] selftests/bpf: Add tests to verify freeing the special fields when update hash and local storage maps
Date: Wed, 5 Nov 2025 10:14:40 +0800 [thread overview]
Message-ID: <697dc64e-8707-44ba-8cda-ba48747f2973@linux.dev> (raw)
In-Reply-To: <02b8c4ba-eb24-41e2-813c-98b83561ef9d@linux.dev>
On 5/11/25 01:30, Yonghong Song wrote:
>
>
> On 10/30/25 8:24 AM, Leon Hwang wrote:
>> Add tests to verify that updating hash and local storage maps decrements
>> refcount when BPF_KPTR_REF objects are involved.
>>
>> The tests perform the following steps:
>>
>> 1. Call update_elem() to insert an initial value.
>> 2. Use bpf_refcount_acquire() to increment the refcount.
>> 3. Store the node pointer in the map value.
>> 4. Add the node to a linked list.
>> 5. Probe-read the refcount and verify it is *2*.
>> 6. Call update_elem() again to trigger refcount decrement.
>> 7. Probe-read the refcount and verify it is *1*.
>>
>> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
>
> I applied this patch only (i.e., not including patches 1/2/3) to master
> branch and do bpf selftest and all tests succeeded.
>
> [root@arch-fb-vm1 bpf]# ./test_progs -t refcounted_kptr
> #294/1 refcounted_kptr/insert_read_both: remove from tree + list:OK
> ...
> #294/18 refcounted_kptr/pcpu_hash_refcount_leak:OK
> #294/19 refcounted_kptr/check_pcpu_hash_refcount:OK
> #294/20 refcounted_kptr/hash_lock_refcount_leak:OK
> #294/21 refcounted_kptr/check_hash_lock_refcount:OK
> #294/22 refcounted_kptr/rbtree_sleepable_rcu:OK
> #294/23 refcounted_kptr/rbtree_sleepable_rcu_no_explicit_rcu_lock:OK
> #294/24 refcounted_kptr/cgroup_storage_lock_refcount_leak:OK
> #294/25 refcounted_kptr/check_cgroup_storage_lock_refcount:OK
> ...
>
> Did I miss anything?
>
Oops.
You should run:
./test_progs -t kptr_refcount
The results are as follows:
test_percpu_hash_refcount_leak:PASS:libbpf_num_possible_cpus 0 nsec
test_percpu_hash_refcount_leak:PASS:calloc values 0 nsec
test_percpu_hash_refcount_leak:PASS:refcounted_kptr__open_and_load 0 nsec
test_refcnt_leak:PASS:bpf_map__update_elem init 0 nsec
test_refcnt_leak:PASS:bpf_prog_test_run_opts 0 nsec
test_refcnt_leak:PASS:refcount 0 nsec
test_refcnt_leak:PASS:bpf_map__update_elem dec refcount 0 nsec
test_refcnt_leak:PASS:bpf_prog_test_run_opts 0 nsec
test_refcnt_leak:FAIL:refcount unexpected refcount: actual 2 != expected 1
#158/1 kptr_refcount_leak/percpu_hash_refcount_leak:FAIL
test_hash_lock_refcount_leak:PASS:refcounted_kptr__open_and_load 0 nsec
test_refcnt_leak:PASS:bpf_map__update_elem init 0 nsec
test_refcnt_leak:PASS:bpf_prog_test_run_opts 0 nsec
test_refcnt_leak:PASS:refcount 0 nsec
test_refcnt_leak:PASS:bpf_map__update_elem dec refcount 0 nsec
test_refcnt_leak:PASS:bpf_prog_test_run_opts 0 nsec
test_refcnt_leak:FAIL:refcount unexpected refcount: actual 2 != expected 1
#158/2 kptr_refcount_leak/hash_lock_refcount_leak:FAIL
test_cgroup_storage_lock_refcount_leak:PASS:setup_cgroup_environment 0 nsec
test_cgroup_storage_lock_refcount_leak:PASS:get_root_cgroup 0 nsec
test_cgroup_storage_lock_refcount_leak:PASS:refcounted_kptr__open_and_load
0 nsec
test_refcnt_leak:PASS:bpf_map__update_elem init 0 nsec
test_refcnt_leak:PASS:bpf_prog_test_run_opts 0 nsec
test_refcnt_leak:PASS:refcount 0 nsec
test_refcnt_leak:PASS:bpf_map__update_elem dec refcount 0 nsec
test_refcnt_leak:PASS:bpf_prog_test_run_opts 0 nsec
test_refcnt_leak:FAIL:refcount unexpected refcount: actual 2 != expected 1
#158/3 kptr_refcount_leak/cgroup_storage_lock_refcount_leak:FAIL
#158 kptr_refcount_leak:FAIL
All error logs:
test_percpu_hash_refcount_leak:PASS:libbpf_num_possible_cpus 0 nsec
test_percpu_hash_refcount_leak:PASS:calloc values 0 nsec
test_percpu_hash_refcount_leak:PASS:refcounted_kptr__open_and_load 0 nsec
test_refcnt_leak:PASS:bpf_map__update_elem init 0 nsec
test_refcnt_leak:PASS:bpf_prog_test_run_opts 0 nsec
test_refcnt_leak:PASS:refcount 0 nsec
test_refcnt_leak:PASS:bpf_map__update_elem dec refcount 0 nsec
test_refcnt_leak:PASS:bpf_prog_test_run_opts 0 nsec
test_refcnt_leak:FAIL:refcount unexpected refcount: actual 2 != expected 1
#158/1 kptr_refcount_leak/percpu_hash_refcount_leak:FAIL
test_hash_lock_refcount_leak:PASS:refcounted_kptr__open_and_load 0 nsec
test_refcnt_leak:PASS:bpf_map__update_elem init 0 nsec
test_refcnt_leak:PASS:bpf_prog_test_run_opts 0 nsec
test_refcnt_leak:PASS:refcount 0 nsec
test_refcnt_leak:PASS:bpf_map__update_elem dec refcount 0 nsec
test_refcnt_leak:PASS:bpf_prog_test_run_opts 0 nsec
test_refcnt_leak:FAIL:refcount unexpected refcount: actual 2 != expected 1
#158/2 kptr_refcount_leak/hash_lock_refcount_leak:FAIL
test_cgroup_storage_lock_refcount_leak:PASS:setup_cgroup_environment 0 nsec
test_cgroup_storage_lock_refcount_leak:PASS:get_root_cgroup 0 nsec
test_cgroup_storage_lock_refcount_leak:PASS:refcounted_kptr__open_and_load
0 nsec
test_refcnt_leak:PASS:bpf_map__update_elem init 0 nsec
test_refcnt_leak:PASS:bpf_prog_test_run_opts 0 nsec
test_refcnt_leak:PASS:refcount 0 nsec
test_refcnt_leak:PASS:bpf_map__update_elem dec refcount 0 nsec
test_refcnt_leak:PASS:bpf_prog_test_run_opts 0 nsec
test_refcnt_leak:FAIL:refcount unexpected refcount: actual 2 != expected 1
#158/3 kptr_refcount_leak/cgroup_storage_lock_refcount_leak:FAIL
#158 kptr_refcount_leak:FAIL
Summary: 0/0 PASSED, 0 SKIPPED, 1 FAILED
All three tests failed because the refcount remained 2 instead of
decreasing to 1 after the second update_elem() call.
The CI result [1] also demonstrates this issue.
Sorry for the misleading test name earlier.
Links:
[1] https://github.com/kernel-patches/bpf/pull/10203
Thanks,
Leon
[...]
next prev parent reply other threads:[~2025-11-05 2:15 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-30 15:24 [PATCH bpf-next v4 0/4] bpf: Free special fields when update hash and local storage maps Leon Hwang
2025-10-30 15:24 ` [PATCH bpf-next v4 1/4] bpf: Free special fields when update [lru_,]percpu_hash maps Leon Hwang
2025-10-30 15:24 ` [PATCH bpf-next v4 2/4] bpf: Free special fields when update hash maps with BPF_F_LOCK Leon Hwang
2025-10-30 15:24 ` [PATCH bpf-next v4 3/4] bpf: Free special fields when update local storage " Leon Hwang
2025-10-30 22:35 ` Alexei Starovoitov
2025-11-03 5:17 ` Leon Hwang
2025-11-03 17:24 ` Alexei Starovoitov
2025-10-30 15:24 ` [PATCH bpf-next v4 4/4] selftests/bpf: Add tests to verify freeing the special fields when update hash and local storage maps Leon Hwang
2025-11-04 17:30 ` Yonghong Song
2025-11-05 2:14 ` Leon Hwang [this message]
2025-11-05 3:35 ` Yonghong Song
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