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ZOOKEEPER-4809: Fix do_completion use-after-free when log level is debug #2139

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ZOOKEEPER-4809: Fix do_completion use-after-free when log level is debug #2139

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12 changes: 8 additions & 4 deletions zookeeper-client/zookeeper-client-c/src/mt_adaptor.c
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Original file line number Diff line number Diff line change
Expand Up @@ -359,6 +359,7 @@ unsigned __stdcall do_io( void * v)
void *do_io(void *v)
#endif
{
log_callback_fn log_fn;
zhandle_t *zh = (zhandle_t*)v;
#ifndef WIN32
struct pollfd fds[2];
Expand Down Expand Up @@ -456,8 +457,9 @@ void *do_io(void *v)
if(is_unrecoverable(zh))
break;
}
api_epilog(zh, 0);
LOG_DEBUG(LOGCALLBACK(zh), "IO thread terminated");
log_fn = LOGCALLBACK(zh);
api_epilog(zh, 0);
LOG_DEBUG(log_fn, "IO thread terminated");
return 0;
}

Expand All @@ -468,6 +470,7 @@ void *do_completion(void *v)
#endif
{
zhandle_t *zh = v;
log_callback_fn fn;
api_prolog(zh);
notify_thread_ready(zh);
LOG_DEBUG(LOGCALLBACK(zh), "started completion thread");
Expand All @@ -479,8 +482,9 @@ void *do_completion(void *v)
pthread_mutex_unlock(&zh->completions_to_process.lock);
process_completions(zh);
}
api_epilog(zh, 0);
LOG_DEBUG(LOGCALLBACK(zh), "completion thread terminated");
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Is it more conventional to swap the two statements ? I saw several return api_epilog(zh, rc) patterns. Also, line 460 has same problem.

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Indeed, it would be conventional to log first and then api_epilog().

But api_epilog() does zookeeper_close() when the rc is zero, i.e. the completion thread is still running after the "terminated" output, which could lead to confusion?

fn = LOGCALLBACK(zh);
api_epilog(zh, 0);
LOG_DEBUG(fn, "completion thread terminated");
return 0;
}

Expand Down