Re: [PATCH v2] perf: report/annotate: fix segfault problem.

[Ingo Molnar <mingo@kernel.org>]

* Wang Nan <wangnan0@huawei.com> wrote:

> perf report and perf annotate are easy to trigger segfault if trace data
> contain kernel module information like this:
> 
>  # perf report -D -i ./perf.data
>  ...
>  0 0 0x188 [0x50]: PERF_RECORD_MMAP -1/0: [0xffffffbff1018000(0xf068000) @ 0]: x [test_module]
>  ...
> 
>  # perf report -i ./perf.data --objdump=/path/to/objdump --kallsyms=/path/to/kallsyms
> 
>  perf: Segmentation fault
>  -------- backtrace --------
>  /path/to/perf[0x503478]
>  /lib64/libc.so.6(+0x3545f)[0x7fb201f3745f]
>  /path/to/perf[0x499b56]
>  /path/to/perf(dso__load_kallsyms+0x13c)[0x49b56c]
>  /path/to/perf(dso__load+0x72e)[0x49c21e]
>  /path/to/perf(map__load+0x6e)[0x4ae9ee]
>  /path/to/perf(thread__find_addr_map+0x24c)[0x47deec]
>  /path/to/perf(perf_event__preprocess_sample+0x88)[0x47e238]
>  /path/to/perf[0x43ad02]
>  /path/to/perf[0x4b55bc]
>  /path/to/perf(ordered_events__flush+0xca)[0x4b57ea]
>  /path/to/perf[0x4b1a01]
>  /path/to/perf(perf_session__process_events+0x3be)[0x4b428e]
>  /path/to/perf(cmd_report+0xf11)[0x43bfc1]
>  /path/to/perf[0x474702]
>  /path/to/perf(main+0x5f5)[0x42de95]
>  /lib64/libc.so.6(__libc_start_main+0xf4)[0x7fb201f23bd4]
>  /path/to/perf[0x42dfc4]
> 
> This is because __kmod_path__parse regard '[' leading name as kernel
> instead of kernel module. The DSO will then be passed to
> dso__load_kernel_sym() then dso__load_kcore() because of --kallsyms
> argument. The segfault is triggered because the kmap structure is not
> initialized.

Could we also make the place that generated the segfault more robust, 
to protect against future mishaps of this type? I suppose the 
non-initialized value was NULL?

Thanks,

	Ingo