Messages in this thread Patch in this message | | | From | Hangliang Lai <> | Subject | [PATCH v3] perf top: expand the range of multithreaded phase | Date | Mon, 10 Apr 2023 21:22:39 +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> --- v2 -> v3 - Sorry for my misunderstanding, patch v3 makes perf_set_multithreaded unconditional after synthesis and set_singlethread in the end.
tools/perf/builtin-top.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c index d4b5b02bab73..ae96ddaf85c4 100644 --- a/tools/perf/builtin-top.c +++ b/tools/perf/builtin-top.c @@ -1273,8 +1273,7 @@ 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(); + perf_set_multithreaded(); if (perf_hpp_list.socket) { ret = perf_env__read_cpu_topology_map(&perf_env); @@ -1352,6 +1351,7 @@ 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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