[PATCH v3] perf tools: perf_event_paranoid and kptr_restrict may crash on 'perf top'

[Jackie Liu]

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.

V2->V3:
free info_linear memory and move code above, don't do those extra btf
checks.

Suggested-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Signed-off-by: Jackie Liu <liuyun01@xxxxxxxxxx>
---
 tools/perf/util/bpf-event.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/bpf-event.c b/tools/perf/util/bpf-event.c
index 57d58c81a5f8..3c03c782bac6 100644
--- a/tools/perf/util/bpf-event.c
+++ b/tools/perf/util/bpf-event.c
@@ -201,12 +201,18 @@ static int perf_event__synthesize_one_bpf_prog(struct perf_session *session,
 	}
 
 	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) {
-- 
2.25.1