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.cnSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

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);