Messages in this thread Patch in this message | | | From | Hangliang Lai <> | Subject | [PATCH v2] perf top: expand the range of multithreaded phase | Date | Thu, 6 Apr 2023 10:53:29 +0800 |
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In __cmd_top, perf_set_multithreaded is used to enable pthread_rwlock, thus donw_read and down_write can work to handle concurrency problems. Then top use perf_set_singlethreaded and switch to single threaded phase, assuming that no thread concurrency will happen later. However, a UAF problem could occur in perf top in single threaded phase, The concurrent procedure is like this: display_thread process_thread -------------- -------------- thread__comm_len -> thread__comm_str -> __thread__comm_str(thread) thread__delete -> comm__free -> comm_str__put -> zfree(&cs->str) -> thread->comm_len = strlen(comm); Since in single thread phase, perf_singlethreaded is true, down_read and down_write can not work to avoid concurrency problems. This patch put perf_set_singlethreaded to the function tail to expand the multithreaded phase range, make display_thread and process_thread run safe.
Signed-off-by: Hangliang Lai <laihangliang1@huawei.com> Reviewed-by: Yunfeng Ye <yeyunfeng@huawei.com> --- v1 -> v2 - Since perf top is always multi-threaded, remove top->nr_threads_synthesize judgment.
tools/perf/builtin-top.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c index d4b5b02bab73..a18db1ee87fa 100644 --- a/tools/perf/builtin-top.c +++ b/tools/perf/builtin-top.c @@ -1242,8 +1242,7 @@ static int __cmd_top(struct perf_top *top) if (perf_session__register_idle_thread(top->session) < 0) return ret; - if (top->nr_threads_synthesize > 1) - perf_set_multithreaded(); + perf_set_multithreaded(); init_process_thread(top); @@ -1273,9 +1272,6 @@ static int __cmd_top(struct perf_top *top) top->evlist->core.threads, true, false, top->nr_threads_synthesize); - if (top->nr_threads_synthesize > 1) - perf_set_singlethreaded(); - if (perf_hpp_list.socket) { ret = perf_env__read_cpu_topology_map(&perf_env); if (ret < 0) { @@ -1352,6 +1348,9 @@ static int __cmd_top(struct perf_top *top) out_join_thread: cond_signal(&top->qe.cond); pthread_join(thread_process, NULL); + + perf_set_singlethreaded(); + return ret; } -- 2.33.0
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