linux-kernel - Re: [PATCH 2/2] perf, tools: Avoid segfault on alias parse error

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Date:   Thu, 17 Aug 2017 08:34:22 -0700
From:   Andi Kleen <andi@...stfloor.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Andi Kleen <andi@...stfloor.org>, jolsa@...nel.org,
        linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 2/2] perf, tools: Avoid segfault on alias parse error

> Humm, but don't we have that checked?

At least not in the case of the segfault below.

-Andi

> 
> void parse_events_evlist_error(struct parse_events_evlist *data,
>                                int idx, const char *str)
> {
>         struct parse_events_error *err = data->error;
> 
>         if (!err)
>                 return;
>         err->idx = idx;
>         err->str = strdup(str);
>         WARN_ONCE(!err->str, "WARNING: failed to allocate error string");
> }
> 
> - Arnaldo
>  
> > Segfault:
> > 
> >     #'0  0x00000000004d66d2 in parse_events_evlist_error (data=0x7fffffffce20, idx=6, str=0x76cda8 "parser error") at util/parse-events.c:2530
> >     #'1  0x0000000000516d0a in parse_events_error (loc=0x7fffffffb210, data=0x7fffffffce20, scanner=0x245b400, msg=0x76cb13 "syntax error") at util/parse-events.y:692
> >     #'2  0x000000000051675b in parse_events_parse (_data=0x7fffffffce20, scanner=0x245b400) at /home/ak/hle/obj-perf/util/parse-events-bison.c:2213
> >     #'3  0x00000000004d3fd6 in parse_events__scanner (str=0x725cff "event=0,", data=0x7fffffffce20, start_token=259) at util/parse-events.c:1646
> >     #'4  0x00000000004d4063 in parse_events_terms (terms=0x245b398, str=0x725cff "event=0,") at util/parse-events.c:1664
> >     #'5  0x00000000005179f1 in __perf_pmu__new_alias (list=0x7fffffffcf90, dir=0x0, name=0x725cec "unc_cha_clockticks", desc=0x725d08 "Uncore cache clock ticks. Unit: uncore_cha ",
> >     val=0x725cff "event=0,", long_desc=0x0, topic=0x725d34 "uncore other", unit=0x0, perpkg=0x6ca7c6 "1", metric_expr=0x0, metric_name=0x0) at util/pmu.c:255
> >     #'6  0x0000000000518789 in pmu_add_cpu_aliases (head=0x7fffffffcf90, name=0x2450903 "uncore_cha_9") at util/pmu.c:571
> >     #'7  0x00000000005188ac in pmu_lookup (name=0x2450903 "uncore_cha_9") at util/pmu.c:613
> >     #'8  0x0000000000518aff in perf_pmu__find (name=0x2450903 "uncore_cha_9") at util/pmu.c:672
> >     #'9  0x00000000005183d5 in pmu_read_sysfs () at util/pmu.c:467
> >     #'10 0x0000000000518a54 in perf_pmu__scan (pmu=0x0) at util/pmu.c:651
> >     #'11 0x0000000000519f26 in print_pmu_events (event_glob=0x0, name_only=false, quiet_flag=false, long_desc=false, details_flag=false) at util/pmu.c:1173
> >     #'12 0x00000000004d5ef0 in print_events (event_glob=0x0, name_only=false, quiet_flag=false, long_desc=false, details_flag=false) at util/parse-events.c:2343
> >     #'13 0x000000000043c7d4 in cmd_list (argc=0, argv=0x7fffffffeb90) at builtin-list.c:56
> >     #'14 0x00000000004ab2c8 in run_builtin (p=0xa281a0 <commands+192>, argc=1, argv=0x7fffffffeb90) at perf.c:296
> >     #15 0x00000000004ab535 in handle_internal_command (argc=1, argv=0x7fffffffeb90) at perf.c:348
> >     #16 0x00000000004ab687 in run_argv (argcp=0x7fffffffe9ec, argv=0x7fffffffe9e0) at perf.c:392
> >     #17 0x00000000004aba55 in main (argc=1, argv=0x7fffffffeb90) at perf.c:530
> >