Messages in this thread | | | Date | Wed, 12 Apr 2023 10:39:25 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH v4] perf top: expand the range of multithreaded phase |
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Em Tue, Apr 11, 2023 at 09:32:24AM +0800, Hangliang Lai escreveu: > 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> > Co-developed-by: Wenyu Liu <liuwenyu7@huawei.com> > Reviewed-by: Yunfeng Ye <yeyunfeng@huawei.com> > Acked-by: Namhyung Kim <namhyung@kernel.org>
Thanks, applied.
- Arnaldo
> --- > v3 -> v4 > - Add Acked-by and Co-developed-by. > > 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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- Arnaldo
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