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 <jolsa@redhat.com>
Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: jackie liu <liuyun01@kylinos.cn>
Link: http://lore.kernel.org/lkml/20210316012453.1156-1-liuyun01@kylinos.cn
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/bpf-event.c b/tools/perf/util/bpf-event.c
index 57d58c81a5f8eb365b7749e90dd2cccf53a5a675..cdecda1ddd36e29eb5d04fbdf8c4bf2fa9c6b393 100644 (file)
--- 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);