linux-kernel - Re: [PATCH v2 perf/core] perf script: fix a use after free crash.

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Message-ID: <20161202071206.GA951@templeofstupid.com>
Date:   Thu, 1 Dec 2016 23:12:06 -0800
From:   Krister Johansen <kjlx@...pleofstupid.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Krister Johansen <kjlx@...pleofstupid.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Frédéric Weisbecker <fweisbec@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 perf/core] perf script: fix a use after free crash.

Hey Arnaldo,

On Tue, Nov 22, 2016 at 04:01:06PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Thu, Nov 10, 2016 at 04:40:46PM -0800, Krister Johansen escreveu:
> > Thanks.  As part of processing this did you run into any problems?
> > Would you like me to rebase against the latest perf/core and re-send the
> > patch?
> 
> Sorry for the overly long delay, trying it now after fixing up a
> conflict with a recent patchkit (branch stuff) I tested it by running
> 'perf top -g' and I'm getting some assertion bugs:

I appreciate you taking another stab at pulling this in.  My turn to
apologize for the delay.

> # perf top -g
>            1.34% filemap_map_pages
>          - 0.59% alloc_pages_vma
>               1.20% __alloc_pages_nodemask
> -    5.87%     0.45%  [kernel]                            [k] handle_mm_fault
>    - 1.94% handle_mm_fault
>         1.34% filemap_map_pages
>       - 0.59% alloc_pages_vma
>            1.22% __alloc_pages_nodemask
> +    5.75%     0.03%  perf                                [.] hist_entry_iter__add
> +    4.46%     0.00%  [unknown]                           [.] 0000000000000000
> -    4.06%     2.74%  libc-2.23.so                        [.] _int_malloc
>    - 1.95% 0
>         1.94% _int_malloc
> -    3.20%     0.23%  perf                                [.] iter_add_next_cumulative_entry
>    - 1.49% iter_add_next_cumulative_entry
>       - 1.43% __hists__add_entry
>      2.58%     0.01%  [kernel]                            [k] return_from_SYSCALL_64
>      2.57%     2.55%  libperl.so.5.22.2                   [.] Perl_fbm_instr
> -    2.54%     2.51%  liblzma.so.5.2.2                    [.] lzma_decode
>    - 2.51% lzma_decode
>      2.33%     0.00%  ld-2.23.so                          [.] _dl_sysdep_start
> +    2.24%     0.04%  ld-2.23.so                          [.] dl_main
>      2.13%     0.03%  [kernel]                            [k] ext4_readdir
>      2.09%     0.01%  [kernel]                            [k] sys_newstat
>      2.08%     0.04%  [kernel]                            [k] vfs_fstatat
>      2.07%     0.02%  [kernel]                            [k] SYSC_newstat
>      2.02%     0.01%  [kernel]                            [k] iterate_dir
> -    1.96%     0.17%  [kernel]                            [k] __alloc_pages_nodemask
>    - 1.37% __alloc_pages_nodemask
> perf: util/map.c:246: map__exit: Assertion `!(!((&map->rb_node)->__rb_parent_color == (unsigned long)(&map->rb_node)))' failed.

Assuming that I'd failed to test 'perf top -g' I went ahead and re-ran
this with the last version of the patch I sent out parented against the
4.8 STABLE branch.  That didn't trigger any assertion failures for me.

Is this branch that gave you merge conflicts now in perf/core or
otherwise publicly avilable?  If so, I'd be happy to try to resolve any
conflicts and re-test against it.  The copy of the patch you sent out
didn't look obviously incorrect.

Thanks,

-K