drbd: Fix five use after free bugs in get_initial_state

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

drbd: Fix five use after free bugs in get_initial_state

In get_initial_state, it calls notify_initial_state_done(skb,..) if

cb->args[5]==1. If genlmsg_put() failed in notify_initial_state_done(),

the skb will be freed by nlmsg_free(skb).

Then get_initial_state will goto out and the freed skb will be used by

return value skb->len, which is a uaf bug.

What's worse, the same problem goes even further: skb can also be

freed in the notify_*_state_change -> notify_*_state calls below.

Thus 4 additional uaf bugs happened.

My patch lets the problem callee functions: notify_initial_state_done

and notify_*_state_change return an error code if errors happen.

So that the error codes could be propagated and the uaf bugs can be avoid.

v2 reports a compilation warning. This v3 fixed this warning and built

successfully in my local environment with no additional warnings.

v2: https://lore.kernel.org/patchwork/patch/1435218/