linux-kernel - [PATCH v3] perf tools: perf_event_paranoid and kptr

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Message-Id: <20210313060246.37116-1-liuyun01@kylinos.cn>
Date:   Sat, 13 Mar 2021 14:02:46 +0800
From:   Jackie Liu <jackieliu2113@...il.com>
To:     jolsa@...hat.com, linux-kernel@...r.kernel.org
Cc:     Jackie Liu <liuyun01@...inos.cn>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>
Subject: [PATCH v3] perf tools: perf_event_paranoid and kptr_restrict may crash on 'perf top'

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@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Signed-off-by: Jackie Liu <liuyun01@...inos.cn>
---
 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