linux-kernel - [PATCH] fix use-after-free in perf_sched_

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Date:   Fri, 3 May 2019 10:35:55 +0800
From:   Wei Li <liwei391@...wei.com>
To:     <acme@...nel.org>, <jolsa@...hat.com>, <namhyung@...nel.org>,
        <alexander.shishkin@...ux.intel.com>, <peterz@...radead.org>,
        <mingo@...hat.com>
CC:     <linux-kernel@...r.kernel.org>, <xiezhipeng1@...wei.com>
Subject: [PATCH] fix use-after-free in perf_sched__lat

After thread is added to machine->threads[i].dead in
__machine__remove_thread, the machine->threads[i].dead is freed
when calling free(session) in perf_session__delete(). So it get a
Segmentation fault when accessing it in thread__put().

In this patch, we delay the perf_session__delete until all threads
have been deleted.

This can be reproduced by following steps:
	ulimit -c unlimited
	export MALLOC_MMAP_THRESHOLD_=0
	perf sched record sleep 10
	perf sched latency --sort max
	Segmentation fault (core dumped)

Signed-off-by: Zhipeng Xie <xiezhipeng1@...wei.com>
Signed-off-by: Wei Li <liwei391@...wei.com>
---
 tools/perf/builtin-sched.c | 44 ++++++++++++++++++++++++++++++++++++--
 1 file changed, 42 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index cbf39dab19c1..17849ae2eb1e 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -3130,11 +3130,48 @@ static void perf_sched__merge_lat(struct perf_sched *sched)
 static int perf_sched__lat(struct perf_sched *sched)
 {
 	struct rb_node *next;
+	const struct perf_evsel_str_handler handlers[] = {
+		{ "sched:sched_switch",	      process_sched_switch_event, },
+		{ "sched:sched_stat_runtime", process_sched_runtime_event, },
+		{ "sched:sched_wakeup",	      process_sched_wakeup_event, },
+		{ "sched:sched_wakeup_new",   process_sched_wakeup_event, },
+		{ "sched:sched_migrate_task", process_sched_migrate_task_event, },
+	};
+	struct perf_session *session;
+	struct perf_data data = {
+		.file      = {
+			.path = input_name,
+		},
+		.mode      = PERF_DATA_MODE_READ,
+		.force     = sched->force,
+	};
+	int rc = -1;
 
 	setup_pager();
 
-	if (perf_sched__read_events(sched))
+	session = perf_session__new(&data, false, &sched->tool);
+	if (session == NULL) {
+		pr_debug("No Memory for session\n");
 		return -1;
+	}
+
+	symbol__init(&session->header.env);
+
+	if (perf_session__set_tracepoints_handlers(session, handlers))
+		goto out_delete;
+
+	if (perf_session__has_traces(session, "record -R")) {
+		int err = perf_session__process_events(session);
+
+		if (err) {
+			pr_err("Failed to process events, error %d", err);
+			goto out_delete;
+		}
+
+		sched->nr_events      = session->evlist->stats.nr_events[0];
+		sched->nr_lost_events = session->evlist->stats.total_lost;
+		sched->nr_lost_chunks = session->evlist->stats.nr_events[PERF_RECORD_LOST];
+	}
 
 	perf_sched__merge_lat(sched);
 	perf_sched__sort_lat(sched);
@@ -3163,7 +3200,10 @@ static int perf_sched__lat(struct perf_sched *sched)
 	print_bad_events(sched);
 	printf("\n");
 
-	return 0;
+	rc = 0;
+out_delete:
+	perf_session__delete(session);
+	return rc;
 }
 
 static int setup_map_cpus(struct perf_sched *sched)
-- 
2.17.1