netdev - Re: [PATCH bpf-next] libbpf: fix memory leak when emitting final btf

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Date:   Mon, 29 Mar 2021 08:54:54 -0700
From:   Song Liu <song@...nel.org>
To:     Andrii Nakryiko <andrii@...nel.org>
Cc:     bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH bpf-next] libbpf: fix memory leak when emitting final btf_ext

On Fri, Mar 26, 2021 at 9:35 PM Andrii Nakryiko <andrii@...nel.org> wrote:
>
> Free temporary allocated memory used to construct finalized .BTF.ext data.
> Found by Coverity static analysis on libbpf's Github repo.
>
> Fixes: 8fd27bf69b86 ("libbpf: Add BPF static linker BTF and BTF.ext support")
> Signed-off-by: Andrii Nakryiko <andrii@...nel.org>

Acked-by: Song Liu <songliubraving@...com>


> ---
>  tools/lib/bpf/linker.c | 24 ++++++++++++++++--------
>  1 file changed, 16 insertions(+), 8 deletions(-)
>
> diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c
> index a29d62ff8041..46b16cbdcda3 100644
> --- a/tools/lib/bpf/linker.c
> +++ b/tools/lib/bpf/linker.c
> @@ -1906,8 +1906,10 @@ static int finalize_btf_ext(struct bpf_linker *linker)
>                         struct dst_sec *sec = &linker->secs[i];
>
>                         sz = emit_btf_ext_data(linker, cur, sec->sec_name, &sec->func_info);
> -                       if (sz < 0)
> -                               return sz;
> +                       if (sz < 0) {
> +                               err = sz;
> +                               goto out;
> +                       }
>
>                         cur += sz;
>                 }
> @@ -1921,8 +1923,10 @@ static int finalize_btf_ext(struct bpf_linker *linker)
>                         struct dst_sec *sec = &linker->secs[i];
>
>                         sz = emit_btf_ext_data(linker, cur, sec->sec_name, &sec->line_info);
> -                       if (sz < 0)
> -                               return sz;
> +                       if (sz < 0) {
> +                               err = sz;
> +                               goto out;
> +                       }
>
>                         cur += sz;
>                 }
> @@ -1936,8 +1940,10 @@ static int finalize_btf_ext(struct bpf_linker *linker)
>                         struct dst_sec *sec = &linker->secs[i];
>
>                         sz = emit_btf_ext_data(linker, cur, sec->sec_name, &sec->core_relo_info);
> -                       if (sz < 0)
> -                               return sz;
> +                       if (sz < 0) {
> +                               err = sz;
> +                               goto out;
> +                       }
>
>                         cur += sz;
>                 }
> @@ -1948,8 +1954,10 @@ static int finalize_btf_ext(struct bpf_linker *linker)
>         if (err) {
>                 linker->btf_ext = NULL;
>                 pr_warn("failed to parse final .BTF.ext data: %d\n", err);
> -               return err;
> +               goto out;
>         }
>
> -       return 0;
> +out:
> +       free(data);
> +       return err;
>  }
> --
> 2.30.2
>