ipmi: Fix use-after-free and list corruption on sender error

In the Linux kernel, the following vulnerability has been resolved:

ipmi: Fix use-after-free and list corruption on sender error

The analysis from Breno:

When the SMI sender returns an error, smi_work() delivers an error

response but then jumps back to restart without cleaning up properly:

1. intf->curr_msg is not cleared, so no new message is pulled

2. newmsg still points to the message, causing sender() to be called

again with the same message

3. If sender() fails again, deliver_err_response() is called with

the same recv_msg that was already queued for delivery

This causes list_add corruption ("list_add double add") because the

recv_msg is added to the user_msgs list twice. Subsequently, the

corrupted list leads to use-after-free when the memory is freed and

reused, and eventually a NULL pointer dereference when accessing

recv_msg->done.

The buggy sequence:

sender() fails

-> deliver_err_response(recv_msg) // recv_msg queued for delivery

-> goto restart // curr_msg not cleared!

sender() fails again (same message!)

-> deliver_err_response(recv_msg) // tries to queue same recv_msg

-> LIST CORRUPTION

Fix this by freeing the message and setting it to NULL on a send error.

Also, always free the newmsg on a send error, otherwise it will leak.