Messages in this thread | | | Subject | Re: [PATCH v2] perf record: Fix coredump with --overwrite and --max-size | From | Yang Jihong <> | Date | Thu, 5 Jan 2023 12:09:17 +0800 |
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Hello,
On 2023/1/4 0:50, Namhyung Kim wrote: > On Mon, Jan 2, 2023 at 8:20 AM Arnaldo Carvalho de Melo <acme@kernel.org> wrote: >> >> Em Thu, Dec 29, 2022 at 12:47:28PM +0000, Yang Jihong escreveu: >>> When --overwrite and --max-size options of perf record are used together, >>> a segmentation fault occurs. The following is an example: >>> >>> # perf record -e sched:sched* --overwrite --max-size 1M -a -- sleep 1 >>> [ perf record: Woken up 1 times to write data ] >>> perf: Segmentation fault >>> Obtained 1 stack frames. >>> [0xc4c67f] >>> Segmentation fault (core dumped) >>> >>> backtrace of the core file is as follows: >>> >>> #0 0x0000000000417990 in process_locked_synthesized_event (tool=0x0, event=0x15, sample=0x1de0, machine=0xf8) at builtin-record.c:630 >>> #1 0x000000000057ee53 in perf_event__synthesize_threads (nr_threads_synthesize=21, mmap_data=<optimized out>, needs_mmap=<optimized out>, machine=0x17ad9b0, process=<optimized out>, tool=0x0) at util/synthetic-events.c:1950 >>> #2 __machine__synthesize_threads (nr_threads_synthesize=0, data_mmap=<optimized out>, needs_mmap=<optimized out>, process=<optimized out>, threads=0x8, target=0x8, tool=0x0, machine=0x17ad9b0) at util/synthetic-events.c:1936 >>> #3 machine__synthesize_threads (machine=0x17ad9b0, target=0x8, threads=0x8, needs_mmap=<optimized out>, data_mmap=<optimized out>, nr_threads_synthesize=0) at util/synthetic-events.c:1947 >>> #4 0x000000000040165d in record__synthesize (tail=<optimized out>, rec=0xbe2520 <record>) at builtin-record.c:2010 >>> #5 0x0000000000403989 in __cmd_record (argc=<optimized out>, argv=<optimized out>, rec=0xbe2520 <record>) at builtin-record.c:2810 >>> #6 0x00000000004196ba in record__init_thread_user_masks (rec=0xbe2520 <record>, cpus=0x17a65f0) at builtin-record.c:3837 >>> #7 record__init_thread_masks (rec=0xbe2520 <record>) at builtin-record.c:3938 >>> #8 cmd_record (argc=1, argv=0x7ffdd692dc60) at builtin-record.c:4241 >>> #9 0x00000000004b701d in pager_command_config (var=0x0, value=0x15 <error: Cannot access memory at address 0x15>, data=0x1de0) at perf.c:117 >>> #10 0x00000000004b732b in get_leaf_frame_caller_aarch64 (sample=0xfffffffb, thread=0x0, usr_idx=<optimized out>) at util/arm64-frame-pointer-unwind-support.c:56 >>> #11 0x0000000000406331 in execv_dashed_external (argv=0x7ffdd692d9e8) at perf.c:410 >>> #12 run_argv (argcp=<synthetic pointer>, argv=<synthetic pointer>) at perf.c:431 >>> #13 main (argc=<optimized out>, argv=0x7ffdd692d9e8) at perf.c:562 >>> >>> The reason is that record__bytes_written accesses the freed memory rec->thread_data, >>> The process is as follows: >>> __cmd_record >>> -> record__free_thread_data >>> -> zfree(&rec->thread_data) // free rec->thread_data >>> -> record__synthesize >>> -> perf_event__synthesize_id_index >>> -> process_synthesized_event >>> -> record__write >>> -> record__bytes_written // access rec->thread_data >>> >>> we only need to check the value of done first. >>> Also add variable check in record__bytes_written for code hardening, >>> and save bytes_written separately to reduce one calculation. >>> >>> Fixes: 6d57581659f7 ("perf record: Add support for limit perf output file size") >>> Signed-off-by: Yang Jihong <yangjihong1@huawei.com> >>> --- >>> >>> Changes since v1: >>> - Add variable check in record__bytes_written for code hardening. >>> - Save bytes_written separately to reduce one calculation. >>> - Remove rec->opts.tail_synthesize check. >> >> Namhyung, are you ok with this now? >> >> - Arnaldo >> >>> tools/perf/builtin-record.c | 26 +++++++++++++++++--------- >>> 1 file changed, 17 insertions(+), 9 deletions(-) >>> >>> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c >>> index 29dcd454b8e2..acba9e43e519 100644 >>> --- a/tools/perf/builtin-record.c >>> +++ b/tools/perf/builtin-record.c >>> @@ -230,16 +230,29 @@ static u64 record__bytes_written(struct record *rec) >>> u64 bytes_written = rec->bytes_written; >>> struct record_thread *thread_data = rec->thread_data; >>> >>> + if (thread_data == NULL) >>> + return bytes_written; >>> + > > Then it won't count bytes written by threads, right? > I think it needs to be saved somewhere. > I'm not sure here. Can you explain it more clearly, thanks :) I can modify it accordingly.
I think if thread_data == NULL, it is not thread data. In this case, we just return rec->bytes_written.
Thanks, Yang
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