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Subject[PATCH v2] fix use-after-free in perf_sched__lat
Date
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@huawei.com>
Signed-off-by: Wei Li <liwei391@huawei.com>
---
tools/perf/builtin-sched.c | 63 ++++++++++++++++++++++++++------------
1 file changed, 43 insertions(+), 20 deletions(-)

diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index 275f2d92a7bf..8a4841fa124c 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -1774,7 +1774,8 @@ static int perf_sched__process_comm(struct perf_tool *tool __maybe_unused,
return 0;
}

-static int perf_sched__read_events(struct perf_sched *sched)
+static int __perf_sched__read_events(struct perf_sched *sched,
+ struct perf_session *session)
{
const struct perf_evsel_str_handler handlers[] = {
{ "sched:sched_switch", process_sched_switch_event, },
@@ -1783,30 +1784,17 @@ static int perf_sched__read_events(struct perf_sched *sched)
{ "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 = {
- .path = input_name,
- .mode = PERF_DATA_MODE_READ,
- .force = sched->force,
- };
- int rc = -1;
-
- 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;
+ return -1;

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;
+ return -1;
}

sched->nr_events = session->evlist->stats.nr_events[0];
@@ -1814,9 +1802,28 @@ static int perf_sched__read_events(struct perf_sched *sched)
sched->nr_lost_chunks = session->evlist->stats.nr_events[PERF_RECORD_LOST];
}

- rc = 0;
-out_delete:
+ return 0;
+}
+
+static int perf_sched__read_events(struct perf_sched *sched)
+{
+ struct perf_session *session;
+ struct perf_data data = {
+ .path = input_name,
+ .mode = PERF_DATA_MODE_READ,
+ .force = sched->force,
+ };
+ int rc;
+
+ session = perf_session__new(&data, false, &sched->tool);
+ if (session == NULL) {
+ pr_debug("No Memory for session\n");
+ return -1;
+ }
+
+ rc = __perf_sched__read_events(sched, session);
perf_session__delete(session);
+
return rc;
}

@@ -3130,12 +3137,25 @@ static void perf_sched__merge_lat(struct perf_sched *sched)

static int perf_sched__lat(struct perf_sched *sched)
{
+ struct perf_session *session;
+ struct perf_data data = {
+ .path = input_name,
+ .mode = PERF_DATA_MODE_READ,
+ .force = sched->force,
+ };
struct rb_node *next;
+ 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;
+ }
+
+ if (__perf_sched__read_events(sched, session))
+ goto out_delete;

perf_sched__merge_lat(sched);
perf_sched__sort_lat(sched);
@@ -3164,7 +3184,10 @@ 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
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