linux-kernel - [PATCH 09/10] perf probe: Avoid calling freeing routine multiple times for same pointer

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Message-Id: <20190723200530.14090-10-acme@kernel.org>
Date:   Tue, 23 Jul 2019 17:05:29 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
        Clark Williams <williams@...hat.com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: [PATCH 09/10] perf probe: Avoid calling freeing routine multiple times for same pointer

From: Arnaldo Carvalho de Melo <acme@...hat.com>

When perf_add_probe_events() we call cleanup_perf_probe_events() for the
pev pointer it receives, then, as part of handling this failure the main
'perf probe' goes on and calls cleanup_params() and that will again call
cleanup_perf_probe_events()for the same pointer, so just set nevents to
zero when handling the failure of perf_add_probe_events() to avoid the
double free.

Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Namhyung Kim <namhyung@...nel.org>
Link: https://lkml.kernel.org/n/tip-x8qgma4g813z96dvtw9w219q@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/builtin-probe.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tools/perf/builtin-probe.c b/tools/perf/builtin-probe.c
index 6418782951a4..3d0ffd41fb55 100644
--- a/tools/perf/builtin-probe.c
+++ b/tools/perf/builtin-probe.c
@@ -698,6 +698,16 @@ __cmd_probe(int argc, const char **argv)
 
 		ret = perf_add_probe_events(params.events, params.nevents);
 		if (ret < 0) {
+
+			/*
+			 * When perf_add_probe_events() fails it calls
+			 * cleanup_perf_probe_events(pevs, npevs), i.e.
+			 * cleanup_perf_probe_events(params.events, params.nevents), which
+			 * will call clear_perf_probe_event(), so set nevents to zero
+			 * to avoid cleanup_params() to call clear_perf_probe_event() again
+			 * on the same pevs.
+			 */
+			params.nevents = 0;
 			pr_err_with_code("  Error: Failed to add events.", ret);
 			return ret;
 		}
-- 
2.21.0