Messages in this thread Patch in this message | | | From | Ian Rogers <> | Date | Wed, 25 Mar 2020 14:35:45 -0700 | Subject | Re: [PATCH] perf parse-events: add defensive null check |
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On Wed, Mar 25, 2020 at 12:25 PM Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com> wrote: > > Em Wed, Mar 25, 2020 at 09:40:22AM -0700, Ian Rogers escreveu: > > Terms may have a null config in which case a strcmp will segv. This can > > be reproduced with: > > perf stat -e '*/event=?,nr/' sleep 1 > > Add a null check to avoid this. This was caught by LLVM's libfuzzer. > > Adding the NULL check doesn't hurt, I guess, but I coudln't repro it: > > [root@seventh ~]# perf stat -e '*/event=?,nr/' sleep 1 > WARNING: multiple event parsing errors > event syntax error: '*/event=?,nr/' > \___ 'nr' is not usable in 'perf stat' > > Initial error: > event syntax error: '*/event=?,nr/' > \___ Cannot find PMU `*'. Missing kernel support? > Run 'perf list' for a list of valid events > > Usage: perf stat [<options>] [<command>] > > -e, --event <event> event selector. use 'perf list' to list available events > [root@seventh ~]# > > Does this take place only when libfuzzer is being used?
Good catch! I was driving the repro through the fuzzer and getting the stack trace below and had assumed this would repro on the command line. I'm now wondering why it won't reproduce :-) I suspect this issue can come up in other scenarios so as you say the null check won't hurt, but the commit message is incorrect.
#0 __interceptor_strcmp () at llvm/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc:448 #1 0x0000555557345eb2 in pmu_resolve_param_term (term=0x607000081190, head_terms=0x602000007cb0, value=0x7ffff4cc0320) at tools/perf/util/pmu.c:994 #2 0x00005555573389a4 in pmu_config_term (formats=0x6080000012c8, attr=0x7ffff4dd4e20, term=0x607000081190, head_terms=0x602000007cb0, zero=false, err=0x7ffff4c90020) at tools/perf/util/pmu.c:1117 #3 0x0000555557337b4e in perf_pmu__config_terms (formats=0x6080000012c8, attr=0x7ffff4dd4e20, head_terms=0x602000007cb0, zero=false, err=0x7ffff4c90020) at tools/perf/util/pmu.c:1154 #4 0x0000555557338f7e in perf_pmu__config (pmu=0x6080000012a0, attr=0x7ffff4dd4e20, head_terms=0x602000007cb0, err=0x7ffff4c90020) at tools/perf/util/pmu.c:1174 #5 0x0000555557314027 in parse_events_add_pmu (parse_state=0x7ffff4c900a0, list=0x602000007e10, name=0x602000001910 "uncore_cha_1", head_config=0x602000007cb0, auto_merge_stats=true, use_alias=false) at tools/perf/util/parse-events.c:1485 #6 0x0000555556d257f9 in parse_events_parse (_parse_state=0x7ffff4c900a0, scanner=0x611000000cc0) at tools/perf/util/parse-events.y:318 #7 0x000055555731c573 in parse_events__scanner (str=0x7ffff4d85c40 "*/event=?,nr/", parse_state=0x7ffff4c900a0, start_token=258) at tools/perf/util/parse-events.c:2026 #8 0x000055555731cbc3 in parse_events (evlist=0x61e000000080, str=0x7ffff4d85c40 "*/event=?,nr/", err=0x7ffff4c90020) at tools/perf/util/parse-events.c:2066
Thanks, Ian
> - Arnaldo > > > Signed-off-by: Ian Rogers <irogers@google.com> > > --- > > tools/perf/util/pmu.c | 11 +++++------ > > 1 file changed, 5 insertions(+), 6 deletions(-) > > > > diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c > > index 616fbda7c3fc..ef6a63f3d386 100644 > > --- a/tools/perf/util/pmu.c > > +++ b/tools/perf/util/pmu.c > > @@ -984,12 +984,11 @@ static int pmu_resolve_param_term(struct parse_events_term *term, > > struct parse_events_term *t; > > > > list_for_each_entry(t, head_terms, list) { > > - if (t->type_val == PARSE_EVENTS__TERM_TYPE_NUM) { > > - if (!strcmp(t->config, term->config)) { > > - t->used = true; > > - *value = t->val.num; > > - return 0; > > - } > > + if (t->type_val == PARSE_EVENTS__TERM_TYPE_NUM && > > + t->config && !strcmp(t->config, term->config)) { > > + t->used = true; > > + *value = t->val.num; > > + return 0; > > } > > } > > > > -- > > 2.25.1.696.g5e7596f4ac-goog > > > > -- > > - Arnaldo
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