Re: [PATCH 0/3] perf record: Fix segfault with '--timestamp-filename' option and pipe mode

[Namhyung Kim]

Hello,

On Thu, Jan 18, 2024 at 8:07 PM Yang Jihong <yangjihong1@xxxxxxxxxx> wrote:
>
> When perf record uses '--timestamp-filename' option and pipe mode,
> will occur segfault:
>
>   # perf record --timestamp-filename -o- true 1>/dev/null
>   [ perf record: Woken up 1 times to write data ]
>   [ perf record: Dump -.2024011813361681 ]
>   perf: Segmentation fault
>   Segmentation fault (core dumped)
>
> Debug the core file by using the gdb:
>
>   # gdb perf core.3706841
>   <SNIP>
>   [New LWP 3706841]
>   [Thread debugging using libthread_db enabled]
>   Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
>   Core was generated by `perf record --timestamp-filename -o- true'.
>   Program terminated with signal SIGSEGV, Segmentation fault.
>   #0  evsel__free_stat_priv (evsel=0x555ea56197af) at util/stat.c:145
>   145             struct perf_stat_evsel *ps = evsel->stats;
>   (gdb) bt
>   #0  evsel__free_stat_priv (evsel=0x555ea56197af) at util/stat.c:145
>   #1  evlist__free_stats (evlist=evlist@entry=0x555bf0dad1b0) at util/stat.c:215
>   #2  0x0000555befd425e8 in evlist__delete (evlist=0x555bf0dad1b0) at util/evlist.c:175
>   #3  0x0000555befd42785 in evlist__delete (evlist=<optimized out>) at util/evlist.c:181
>   #4  0x0000555befc7f547 in cmd_record (argc=<optimized out>, argv=<optimized out>) at builtin-record.c:4252
>   #5  0x0000555befd27700 in run_builtin (p=p@entry=0x555bf05acf88 <commands+264>, argc=argc@entry=4, argv=argv@entry=0x7ffc2696a920) at perf.c:349
>   #6  0x0000555befc68751 in handle_internal_command (argv=0x7ffc2696a920, argc=4) at perf.c:402
>   #7  run_argv (argv=<synthetic pointer>, argcp=<synthetic pointer>) at perf.c:446
>   #8  main (argc=4, argv=0x7ffc2696a920) at perf.c:562
>
> It is found that the memory of the evsel is modified.
> The reason is that perf_data__switch() not initialized 'new_filename',
> as a result, it uses the on-stack variable. It happens that the evsel
> address is stored here. 'new_filename' is freed later when uses
> '--timestamp-filename' option. Therefore, segfault occurs in the evsel_delete().
>
>
> 1. patch1 fixes this problem.
> 2. patch2 to optimize the process, check conflict between
>    '--timestamp-filename' option and the pipe mode before recording to
>    avoid switch perf data.
> 3. patch3 fixes the code style problem by the way.
>
>
> Yang Jihong (3):
>   perf record: Fix possible incorrect free in record__switch_output()
>   perf record: Check conflict between '--timestamp-filename' option and
>     pipe mode before recording
>   perf data: Minor code style alignment cleanup

Acked-by: Namhyung Kim <namhyung@xxxxxxxxxx>

Thanks,
Namhyung

>
>  tools/perf/builtin-record.c | 14 ++++++++++----
>  tools/perf/util/data.c      | 10 ++++------
>  tools/perf/util/data.h      |  6 +++---
>  3 files changed, 17 insertions(+), 13 deletions(-)
>
> --
> 2.34.1
>