From: Ihor Solodrai <ihor.solodrai@linux.dev>
To: Jiri Olsa <olsajiri@gmail.com>
Cc: "Alexei Starovoitov" <ast@kernel.org>,
"Andrii Nakryiko" <andrii@kernel.org>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Eduard Zingerman" <eddyz87@gmail.com>,
"Amery Hung" <ameryhung@gmail.com>,
"Mykyta Yatsenko" <yatsenko@meta.com>,
"Alexis Lothoré" <alexis.lothore@bootlin.com>,
bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-team@meta.com
Subject: Re: [PATCH bpf-next v1 04/14] selftests/bpf: Refactor bpf_get_ksyms() trace helper
Date: Tue, 17 Feb 2026 12:42:08 -0800 [thread overview]
Message-ID: <8c1527fd-7c57-488a-b4a6-3b763f3b5746@linux.dev> (raw)
In-Reply-To: <aY25gB6NDmlPJPUB@krava>
On 2/12/26 3:29 AM, Jiri Olsa wrote:
> On Wed, Feb 11, 2026 at 05:13:46PM -0800, Ihor Solodrai wrote:
>> ASAN reported a memory leak in bpf_get_ksyms(): it allocates a struct
>> ksyms internally and never frees it.
>>
>> Moe struct ksyms to trace_helpers.h and return it from the
>> bpf_get_ksyms(), giving ownership to the caller. Add filtered_syms and
>> filtered_cnt fields to the ksyms to hold the filtered array of
>> symbols, previously returned by bpf_get_ksyms().
>>
>> Fixup the call sites: kprobe_multi_test and bench_trigger.
>>
>> Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
>> ---
>> .../selftests/bpf/benchs/bench_trigger.c | 9 ++++----
>> .../bpf/prog_tests/kprobe_multi_test.c | 12 ++++------
>> tools/testing/selftests/bpf/trace_helpers.c | 23 ++++++++++---------
>> tools/testing/selftests/bpf/trace_helpers.h | 11 +++++++--
>> 4 files changed, 30 insertions(+), 25 deletions(-)
>>
>> diff --git a/tools/testing/selftests/bpf/benchs/bench_trigger.c b/tools/testing/selftests/bpf/benchs/bench_trigger.c
>> index aeec9edd3851..7231b88cf21a 100644
>> --- a/tools/testing/selftests/bpf/benchs/bench_trigger.c
>> +++ b/tools/testing/selftests/bpf/benchs/bench_trigger.c
>> @@ -230,8 +230,7 @@ static void trigger_fentry_setup(void)
>> static void attach_ksyms_all(struct bpf_program *empty, bool kretprobe)
>> {
>> LIBBPF_OPTS(bpf_kprobe_multi_opts, opts);
>> - char **syms = NULL;
>> - size_t cnt = 0;
>> + struct ksyms *ksyms = NULL;
>>
>> /* Some recursive functions will be skipped in
>> * bpf_get_ksyms -> skip_entry, as they can introduce sufficient
>> @@ -241,13 +240,13 @@ static void attach_ksyms_all(struct bpf_program *empty, bool kretprobe)
>> * So, don't run the kprobe-multi-all and kretprobe-multi-all on
>> * a debug kernel.
>> */
>> - if (bpf_get_ksyms(&syms, &cnt, true)) {
>> + if (bpf_get_ksyms(&ksyms, true)) {
>> fprintf(stderr, "failed to get ksyms\n");
>> exit(1);
>> }
>>
>> - opts.syms = (const char **) syms;
>> - opts.cnt = cnt;
>> + opts.syms = (const char **)ksyms->filtered_syms;
>> + opts.cnt = ksyms->filtered_cnt;
>> opts.retprobe = kretprobe;
>> /* attach empty to all the kernel functions except bpf_get_numa_node_id. */
>> if (!bpf_program__attach_kprobe_multi_opts(empty, NULL, &opts)) {
>
> hi,
>
> missing free_kallsyms_local call in here ?
Yeap, thanks.
>
>
>> diff --git a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
>> index 9caef222e528..f81dcd609ee9 100644
>> --- a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
>> +++ b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
>> @@ -456,25 +456,23 @@ static void test_kprobe_multi_bench_attach(bool kernel)
>> {
>> LIBBPF_OPTS(bpf_kprobe_multi_opts, opts);
>> struct kprobe_multi_empty *skel = NULL;
>> - char **syms = NULL;
>> - size_t cnt = 0;
>> + struct ksyms *ksyms = NULL;
>>
>> - if (!ASSERT_OK(bpf_get_ksyms(&syms, &cnt, kernel), "bpf_get_ksyms"))
>> + if (!ASSERT_OK(bpf_get_ksyms(&ksyms, kernel), "bpf_get_ksyms"))
>> return;
>>
>> skel = kprobe_multi_empty__open_and_load();
>> if (!ASSERT_OK_PTR(skel, "kprobe_multi_empty__open_and_load"))
>> goto cleanup;
>>
>> - opts.syms = (const char **) syms;
>> - opts.cnt = cnt;
>> + opts.syms = (const char **)ksyms->filtered_syms;
>> + opts.cnt = ksyms->filtered_cnt;
>>
>> do_bench_test(skel, &opts);
>>
>> cleanup:
>> kprobe_multi_empty__destroy(skel);
>> - if (syms)
>> - free(syms);
>> + free_kallsyms_local(ksyms);
>> }
>>
>> static void test_kprobe_multi_bench_attach_addr(bool kernel)
>> diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c
>> index eeaab7013ca2..0e63daf83ed5 100644
>> --- a/tools/testing/selftests/bpf/trace_helpers.c
>> +++ b/tools/testing/selftests/bpf/trace_helpers.c
>> @@ -24,12 +24,6 @@
>> #define TRACEFS_PIPE "/sys/kernel/tracing/trace_pipe"
>> #define DEBUGFS_PIPE "/sys/kernel/debug/tracing/trace_pipe"
>>
>> -struct ksyms {
>> - struct ksym *syms;
>> - size_t sym_cap;
>> - size_t sym_cnt;
>> -};
>> -
>> static struct ksyms *ksyms;
>> static pthread_mutex_t ksyms_mutex = PTHREAD_MUTEX_INITIALIZER;
>>
>> @@ -54,6 +48,8 @@ void free_kallsyms_local(struct ksyms *ksyms)
>> if (!ksyms)
>> return;
>>
>> + free(ksyms->filtered_syms);
>> +
>> if (!ksyms->syms) {
>> free(ksyms);
>> return;
>> @@ -610,7 +606,7 @@ static int search_kallsyms_compare(const void *p1, const struct ksym *p2)
>> return compare_name(p1, p2->name);
>> }
>>
>> -int bpf_get_ksyms(char ***symsp, size_t *cntp, bool kernel)
>> +int bpf_get_ksyms(struct ksyms **ksymsp, bool kernel)
>> {
>> size_t cap = 0, cnt = 0;
>> char *name = NULL, *ksym_name, **syms = NULL;
>> @@ -637,8 +633,10 @@ int bpf_get_ksyms(char ***symsp, size_t *cntp, bool kernel)
>> else
>> f = fopen("/sys/kernel/debug/tracing/available_filter_functions", "r");
>>
>> - if (!f)
>> + if (!f) {
>> + free_kallsyms_local(ksyms);
>> return -EINVAL;
>> + }
>>
>> map = hashmap__new(symbol_hash, symbol_equal, NULL);
>> if (IS_ERR(map)) {
>> @@ -679,15 +677,18 @@ int bpf_get_ksyms(char ***symsp, size_t *cntp, bool kernel)
>> syms[cnt++] = ksym_name;
>> }
>>
>> - *symsp = syms;
>> - *cntp = cnt;
>> + ksyms->filtered_syms = syms;
>> + ksyms->filtered_cnt = cnt;
>> + *ksymsp = ksyms;
>>
>> error:
>> free(name);
>> fclose(f);
>> hashmap__free(map);
>> - if (err)
>> + if (err) {
>> free(syms);
>> + free_kallsyms_local(ksyms);
>> + }
>
> I think we could just call free_kallsyms_local unconditionally in here
> and fix callers to free syms pointer? seems easier than adding filtered*
> fields to ksyms
The strings in filtered_syms are ksyms->syms[i].name pointers (not
copied). I didn't want to do another strdup, and I also didn't like
passing three out parameters to bpf_get_ksyms().
So I decided to consolidate the data gathered by bpf_get_ksyms() in
struct ksyms. ksyms->filtered_syms essentially is a view into the
ksyms->syms, and it can be unused too.
Does this make sense?
>
> thanks,
> jirak
>
>
>> return err;
>> }
>>
>> diff --git a/tools/testing/selftests/bpf/trace_helpers.h b/tools/testing/selftests/bpf/trace_helpers.h
>> index a5576b2dfc26..d5bf1433675d 100644
>> --- a/tools/testing/selftests/bpf/trace_helpers.h
>> +++ b/tools/testing/selftests/bpf/trace_helpers.h
>> @@ -23,7 +23,14 @@ struct ksym {
>> long addr;
>> char *name;
>> };
>> -struct ksyms;
>> +
>> +struct ksyms {
>> + struct ksym *syms;
>> + size_t sym_cap;
>> + size_t sym_cnt;
>> + char **filtered_syms;
>> + size_t filtered_cnt;
>> +};
>>
>> typedef int (*ksym_cmp_t)(const void *p1, const void *p2);
>> typedef int (*ksym_search_cmp_t)(const void *p1, const struct ksym *p2);
>> @@ -53,7 +60,7 @@ ssize_t get_rel_offset(uintptr_t addr);
>>
>> int read_build_id(const char *path, char *build_id, size_t size);
>>
>> -int bpf_get_ksyms(char ***symsp, size_t *cntp, bool kernel);
>> +int bpf_get_ksyms(struct ksyms **ksymsp, bool kernel);
>> int bpf_get_addrs(unsigned long **addrsp, size_t *cntp, bool kernel);
>>
>> #endif
>> --
>> 2.53.0
>>
>>
next prev parent reply other threads:[~2026-02-17 20:42 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-12 1:13 [PATCH bpf-next v1 00/14] selftests/bpf: Fixes for userspace ASAN Ihor Solodrai
2026-02-12 1:13 ` [PATCH bpf-next v1 01/14] selftests/bpf: Pass through build flags to bpftool and resolve_btfids Ihor Solodrai
2026-02-12 2:39 ` Alexei Starovoitov
2026-02-12 3:08 ` Ihor Solodrai
2026-02-13 0:08 ` Ihor Solodrai
2026-02-12 1:13 ` [PATCH bpf-next v1 02/14] resolve_btfids: Fix memory leaks reported by ASAN Ihor Solodrai
2026-02-12 11:28 ` Jiri Olsa
2026-02-12 1:13 ` [PATCH bpf-next v1 03/14] selftests/bpf: Add DENYLIST.asan Ihor Solodrai
2026-02-12 1:13 ` [PATCH bpf-next v1 04/14] selftests/bpf: Refactor bpf_get_ksyms() trace helper Ihor Solodrai
2026-02-12 11:29 ` Jiri Olsa
2026-02-17 20:42 ` Ihor Solodrai [this message]
2026-02-18 13:14 ` Jiri Olsa
2026-02-13 9:56 ` Alexis Lothoré
2026-02-12 1:13 ` [PATCH bpf-next v1 05/14] selftests/bpf: Fix memory leaks in tests Ihor Solodrai
2026-02-12 23:08 ` Eduard Zingerman
2026-02-12 1:13 ` [PATCH bpf-next v1 06/14] selftests/bpf: Fix cleanup in check_fd_array_cnt__fd_array_too_big() Ihor Solodrai
2026-02-12 23:17 ` Eduard Zingerman
2026-02-12 1:13 ` [PATCH bpf-next v1 07/14] veristat: Fix a memory leak for preset ENUMERATOR Ihor Solodrai
2026-02-12 13:37 ` Mykyta Yatsenko
2026-02-12 1:13 ` [PATCH bpf-next v1 08/14] selftests/bpf: Fix use-after-free in xdp_metadata test Ihor Solodrai
2026-02-12 13:40 ` Mykyta Yatsenko
2026-02-12 1:13 ` [PATCH bpf-next v1 09/14] selftests/bpf: Fix double thread join in uprobe_multi_test Ihor Solodrai
2026-02-12 11:29 ` Jiri Olsa
2026-02-12 14:49 ` Mykyta Yatsenko
2026-02-13 16:48 ` Jiri Olsa
2026-02-12 1:13 ` [PATCH bpf-next v1 10/14] selftests/bpf: Fix resource leaks caused by missing cleanups Ihor Solodrai
2026-02-13 0:45 ` Eduard Zingerman
2026-02-12 1:13 ` [PATCH bpf-next v1 11/14] selftests/bpf: Free bpf_object in test_sysctl Ihor Solodrai
2026-02-13 0:54 ` Eduard Zingerman
2026-02-12 1:13 ` [PATCH bpf-next v1 12/14] selftests/bpf: Fix array bounds warning in jit_disasm_helpers Ihor Solodrai
2026-02-13 1:02 ` Eduard Zingerman
2026-02-12 1:13 ` [PATCH bpf-next v1 13/14] selftests/bpf: Fix out-of-bounds array access bugs reported by ASAN Ihor Solodrai
2026-02-13 1:11 ` Eduard Zingerman
2026-02-17 23:27 ` Ihor Solodrai
2026-02-12 1:13 ` [PATCH bpf-next v1 14/14] selftests/bpf: Check BPFTOOL env var in detect_bpftool_path() Ihor Solodrai
2026-02-12 15:03 ` Mykyta Yatsenko
2026-02-13 10:36 ` Alexis Lothoré
2026-02-12 22:00 ` [PATCH bpf-next v1 00/14] selftests/bpf: Fixes for userspace ASAN Eduard Zingerman
2026-02-12 23:57 ` Ihor Solodrai
2026-02-13 0:23 ` Eduard Zingerman
2026-02-13 16:13 ` Ihor Solodrai
2026-02-13 18:06 ` Eduard Zingerman
2026-02-12 23:26 ` Eduard Zingerman
2026-02-13 17:56 ` Ihor Solodrai
2026-02-13 18:09 ` Eduard Zingerman
2026-02-13 18:29 ` Ihor Solodrai
2026-02-13 18:35 ` Eduard Zingerman
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