From: Jiri Olsa <olsajiri@gmail.com>
To: Ihor Solodrai <ihor.solodrai@linux.dev>
Cc: "Jiri Olsa" <olsajiri@gmail.com>,
"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: Wed, 18 Feb 2026 14:14:26 +0100 [thread overview]
Message-ID: <aZW7Mp6DnOBfeQq0@krava> (raw)
In-Reply-To: <8c1527fd-7c57-488a-b4a6-3b763f3b5746@linux.dev>
On Tue, Feb 17, 2026 at 12:42:08PM -0800, Ihor Solodrai wrote:
> 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?
yep, sounds good
thanks,
jirka
next prev parent reply other threads:[~2026-02-18 13:14 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
2026-02-18 13:14 ` Jiri Olsa [this message]
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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