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[37.188.249.12]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-483983fd224sm2137585e9.28.2026.02.17.14.06.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 17 Feb 2026 14:06:04 -0800 (PST) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Tue, 17 Feb 2026 23:05:57 +0100 To: bot+bpf-ci@kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, bpf@vger.kernel.org, linux-trace-kernel@vger.kernel.org, kafai@fb.com, eddyz87@gmail.com, songliubraving@fb.com, yhs@fb.com, menglong8.dong@gmail.com, rostedt@kernel.org, martin.lau@kernel.org, yonghong.song@linux.dev, clm@meta.com, ihor.solodrai@linux.dev Subject: Re: [RFC bpf-next 09/12] libbpf: Add support to create tracing multi link Message-ID: References: <20260203093819.2105105-10-jolsa@kernel.org> <9c8e4f31ee1d79f8ae145ec1c4d388f0829a77f1a75e8ec80e1d4bcf00bde751@mail.kernel.org> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9c8e4f31ee1d79f8ae145ec1c4d388f0829a77f1a75e8ec80e1d4bcf00bde751@mail.kernel.org> On Tue, Feb 03, 2026 at 10:14:03AM +0000, bot+bpf-ci@kernel.org wrote: > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > > index 0c8bf0b5c..a16243300 100644 > > --- a/tools/lib/bpf/libbpf.c > > +++ b/tools/lib/bpf/libbpf.c > > [ ... ] > > > +struct bpf_link * > > +bpf_program__attach_tracing_multi(const struct bpf_program *prog, const char *pattern, > > + const struct bpf_tracing_multi_opts *opts) > > +{ > > + LIBBPF_OPTS(bpf_link_create_opts, lopts); > > + __u32 *btf_ids, cnt, *free_ids = NULL; > > + int prog_fd, link_fd, err; > > + struct bpf_link *link; > > + > > + btf_ids = OPTS_GET(opts, btf_ids, false); > > + cnt = OPTS_GET(opts, cnt, false); > > + > > + if (!pattern && !btf_ids && !cnt) > > + return libbpf_err_ptr(-EINVAL); > > + if (pattern && (btf_ids || cnt)) > > + return libbpf_err_ptr(-EINVAL); > > + > > + if (pattern) { > > + err = bpf_object__load_vmlinux_btf(prog->obj, true); > > + if (err) > > + return libbpf_err_ptr(err); > > + > > + cnt = btf__find_by_glob_kind(prog->obj->btf_vmlinux, BTF_KIND_FUNC, > > + pattern, NULL, &btf_ids); > > + if (cnt <= 0) > > + return libbpf_err_ptr(-EINVAL); > > + free_ids = btf_ids; > > + } > > + > > + lopts.tracing_multi.btf_ids = btf_ids; > > + lopts.tracing_multi.btf_ids_cnt = cnt; > > + > > + link = calloc(1, sizeof(*link)); > > + if (!link) > > + return libbpf_err_ptr(-ENOMEM); > > If calloc fails here and pattern was provided, btf__find_by_glob_kind() will > have allocated btf_ids (tracked by free_ids). Does this leak free_ids? The > error label below frees it properly, but this return bypasses that path. > > Something like: > > if (!link) { > free(free_ids); > return libbpf_err_ptr(-ENOMEM); > } > > or using goto error would fix this. yep, will fix > > > + link->detach = &bpf_link__detach_fd; > > + > > + prog_fd = bpf_program__fd(prog); > > + link_fd = bpf_link_create(prog_fd, 0, prog->expected_attach_type, &lopts); > > + if (link_fd < 0) { > > + err = -errno; > > + pr_warn("prog '%s': failed to attach: %s\n", prog->name, errstr(err)); > > + goto error; > > + } > > + link->fd = link_fd; > > + free(free_ids); > > + return link; > > +error: > > + free(link); > > + free(free_ids); > > + return libbpf_err_ptr(err); > > +} > > + > > +static int attach_tracing_multi(const struct bpf_program *prog, long cookie, struct bpf_link **link) > > +{ > > + const char *spec; > > + char *pattern; > > + bool is_fexit; > > + int n; > > + > > + /* no auto-attach for SEC("fentry.multi") and SEC("fexit.multi") */ > > + if (strcmp(prog->sec_name, "fentry.multi") == 0 || > > + strcmp(prog->sec_name, "fexit.multi") == 0) > > + return 0; > > + > > + is_fexit = str_has_pfx(prog->sec_name, "fexit.multi/"); > > + if (is_fexit) > > + spec = prog->sec_name + sizeof("fexit.multi/") - 1; > > + else > > + spec = prog->sec_name + sizeof("fentry.multi/") - 1; > > + > > + n = sscanf(spec, "%m[a-zA-Z0-9_.*?]", &pattern); > > + if (n < 1) { > > + pr_warn("tracing multi pattern is invalid: %s\n", pattern); > > When sscanf fails to match (n < 1), pattern is never assigned because %m only > allocates on successful match. Should this print spec instead of the > uninitialized pattern? Compare with attach_kprobe_multi() which uses: > > pr_warn("kprobe multi pattern is invalid: %s\n", spec); yes > > > + return -EINVAL; > > + } > > + > > + *link = bpf_program__attach_tracing_multi(prog, pattern, NULL); > > + return libbpf_get_error(*link); > > Is pattern being leaked here? sscanf with %m allocates the string, but there > is no free(pattern) before returning. Compare with attach_kprobe_multi(): > > *link = bpf_program__attach_kprobe_multi_opts(prog, pattern, &opts); > free(pattern); > return libbpf_get_error(*link); yep, will fix, thnx jirka