Access freed memory in connect on username

[gajanak]

Hello,

I noticed the following behavior on connect with different connection option.

1. Connect with username/password
2. Connect without username/password

On second connect the first username/password is used again.

Using the current "master" Branch.

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IMHO:

On connect the username/password is copied from options in MQTTClient.username/password. If I call connect a second time without username (null) in options, the memory of MQTTClient.username is freed, but the pointer is not set to zero ;). Now the freed pointer still directing to the previous username is used for connect. Its lucky, if the memory is still valid.

https://github.com/eclipse/paho.mqtt.c/blob/master/src/MQTTClient.c#L1614

	if (m->c->username)
		free((void*)m->c->username);
	if (options->username)
		m->c->username = MQTTStrdup(options->username);

It seems m->c->username should be zeroed after free or set to zero in else-branch of options->username check ?

Perhaps I missed something.....

[icraggs]

Yes, setting the pointer to NULL after being freed should be done.