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SubjectRe: [PATCH 1/2] perf parse-events: Fix segfault when event parser gets an error
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On 19/07/22 04:10, Ian Rogers wrote:
> On Tue, Jul 12, 2022 at 4:28 AM Adrian Hunter <adrian.hunter@intel.com> wrote:
>>
>> parse_events() is often called with parse_events_error set to NULL.
>> Make parse_events_error__handle() not segfault in that case.
>>
>> Fixes: 43eb05d06679 ("perf tests: Support 'Track with sched_switch' test for hybrid")
>> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
>> ---
>> tools/perf/util/parse-events.c | 14 +++++++++++---
>> 1 file changed, 11 insertions(+), 3 deletions(-)
>>
>> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
>> index 7ed235740431..700c95eafd62 100644
>> --- a/tools/perf/util/parse-events.c
>> +++ b/tools/perf/util/parse-events.c
>> @@ -2391,9 +2391,12 @@ void parse_events_error__exit(struct parse_events_error *err)
>> void parse_events_error__handle(struct parse_events_error *err, int idx,
>> char *str, char *help)
>> {
>> - if (WARN(!str, "WARNING: failed to provide error string\n")) {
>> - free(help);
>> - return;
>> + if (WARN(!str, "WARNING: failed to provide error string\n"))
>> + goto out_free;
>> + if (!err) {
>> + /* Assume caller does not want message printed */
>> + pr_debug("event syntax error: %s\n", str);
>> + goto out_free;
>
>
> It feels like a simpler invariant (as done elsewhere) to have the
> caller always pass err and then in the caller to call
> parse_events_error__exit. Any reason for behavior change?

This is a bug fix. More complicated changes can be done separately,
if desired, but it is wrong to segfault here in any case.

>
> Thanks,
> Ian
>
>> }
>> switch (err->num_errors) {
>> case 0:
>> @@ -2419,6 +2422,11 @@ void parse_events_error__handle(struct parse_events_error *err, int idx,
>> break;
>> }
>> err->num_errors++;
>> + return;
>> +
>> +out_free:
>> + free(str);
>> + free(help);
>> }
>>
>> #define MAX_WIDTH 1000
>> --
>> 2.25.1
>>

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