Em Tue, Mar 16, 2021 at 09:24:53AM +0800, Jackie Liu escreveu:
> After install the libelf-dev package and compiling perf, kptr_restrict=2
> and perf_event_paranoid=3 will cause perf top to crash, because the
> value of /proc/kallsyms cannot be obtained, which leads to
> info->jited_ksyms == NULL. In order to solve this problem, Add a
> judgment before use.
>
> v3->v4:
> Fix memory leaks in more places
>
> v2->v3:
> free info_linear memory and move code above, don't do those extra btf
> checks.
Applied, edited the commit message to:
----
perf top: Fix BPF support related crash with perf_event_paranoid=3 +
kptr_restrict
After installing the libelf-dev package and compiling perf, if we have
kptr_restrict=2 and perf_event_paranoid=3 'perf top' will crash because
the value of /proc/kallsyms cannot be obtained, which leads to
info->jited_ksyms == NULL. In order to solve this problem, Add a
check before use.
Also plug some leaks on the error path.
----
> Suggested-by: Jiri Olsa <jo...@redhat.com>
> Cc: Peter Zijlstra <pet...@infradead.org>
> Cc: Ingo Molnar <mi...@redhat.com>
> Cc: Arnaldo Carvalho de Melo <a...@kernel.org>
> Cc: Mark Rutland <mark.rutl...@arm.com>
> Cc: Alexander Shishkin <alexander.shish...@linux.intel.com>
> Cc: Namhyung Kim <namhy...@kernel.org>
> Signed-off-by: Jackie Liu <liuyu...@kylinos.cn>
> ---
> tools/perf/util/bpf-event.c | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/tools/perf/util/bpf-event.c b/tools/perf/util/bpf-event.c
> index 57d58c81a5f8..cdecda1ddd36 100644
> --- a/tools/perf/util/bpf-event.c
> +++ b/tools/perf/util/bpf-event.c
> @@ -196,25 +196,32 @@ static int perf_event__synthesize_one_bpf_prog(struct
> perf_session *session,
> }
>
> if (info_linear->info_len < offsetof(struct bpf_prog_info, prog_tags)) {
> + free(info_linear);
> pr_debug("%s: the kernel is too old, aborting\n", __func__);
> return -2;
> }
>
> info = &info_linear->info;
> + if (!info->jited_ksyms) {
> + free(info_linear);
> + return -1;
> + }
>
> /* number of ksyms, func_lengths, and tags should match */
> sub_prog_cnt = info->nr_jited_ksyms;
> if (sub_prog_cnt != info->nr_prog_tags ||
> - sub_prog_cnt != info->nr_jited_func_lens)
> + sub_prog_cnt != info->nr_jited_func_lens) {
> + free(info_linear);
> return -1;
> + }
>
> /* check BTF func info support */
> if (info->btf_id && info->nr_func_info && info->func_info_rec_size) {
> /* btf func info number should be same as sub_prog_cnt */
> if (sub_prog_cnt != info->nr_func_info) {
> pr_debug("%s: mismatch in BPF sub program count and BTF
> function info count, aborting\n", __func__);
> - err = -1;
> - goto out;
> + free(info_linear);
> + return -1;
> }
> if (btf__get_from_id(info->btf_id, &btf)) {
> pr_debug("%s: failed to get BTF of id %u, aborting\n",
> __func__, info->btf_id);
> --
> 2.25.1
>
--
- Arnaldo
