Abnormal Segment Error Problem in version 1.2.18

[breadmechanic]

I found a problem in zlog 1.2.18. When the vzlog interface is used to print logs, the Signal 11 exception occurs. As a result, the process exits.
Parse the library file and find that the following code is incorrect. The code is in the zlog.c file.

void vzlog(...)
{
	if (zlog_category_needless_level(category, level)) return;
...
}

The contents of the expanded macro definition are as follows:

#define zlog_category_needless_level(a_category, lv) \
        a_category && (zlog_env_conf->level > lv || !((a_category->level_bitmap[lv/8] >> (7 - lv % 8)) & 0x01))

By checking the assembly code, we find that the Linux is accessing zlog_env_conf->level when the problem occurs. The null pointer may occur when the parameter is accessed.

I hope you can help analyze the possible causes and assist in fixing the problem.

[breadmechanic]

Some additional information:

I was using zlog version 1.2.16 and recently switched to 1.2.18.

The preceding code snippets are modified in version 1.2.17. The Pull Request is #159

The only change is that the determination of zlog_env_conf->level > lv is added.

1.2.16 version of the code is as follows:

#define zlog_category_needless_level(a_category, lv) \
    (a_category && !((a_category->level_bitmap[lv/8] >> (7 - lv % 8)) & 0x01))

1.2.17 version of the code is as follows:

#define zlog_category_needless_level(a_category, lv) \
        a_category && (zlog_env_conf->level > lv || !((a_category->level_bitmap[lv/8] >> (7 - lv % 8)) & 0x01))

[findix]

#159 also make a ERROR (1891873:level_list.c:141) str is [], can't find level error if don't set log level in the config file.

[breadmechanic]

When the following two processes are triggered at the same time, a serious concurrency problem occurs. As a result, a null pointer occurs when the variable zlog_env_conf is accessed.

Process 1:

void vzlog(...)
{
    if (zlog_category_needless_level(category, level)) return;
    ...
}

Process 2:

int zlog_reload(...)
{
    rc = pthread_rwlock_wrlock(&zlog_env_lock);
    ...
    zlog_conf_del(zlog_env_conf);
    zlog_env_conf = new_conf;
    ...
    rc = pthread_rwlock_unlock(&zlog_env_lock);
}

If we have two threads in a single process and call these two functions at the same point in time, there is a serious concurrency problem.

The problem is caused by the code #159 modified in zlog 1.2.17.

The access to zlog_env_conf is added to the macro definition zlog_category_needless_level, but pthread_rwlock_wrlock is not invoked to lock. As a result, zlog_conf_del is invoked in zlog_reload. There is a low probability that the zlog_env_conf accessed by other threads is a null pointer.

This is a serious abnormal segment error problem. We hope that the problem can be solved as soon as possible and a patch or a new version can be provided.