Re: [PATCH] uprobes: Free utask on dup_return_instance() failure

[Oleg Nesterov <oleg@redhat.com>]

On 08/24, Keke Ming wrote:
>
> > Note that uprobe_copy_process() warns but returns "void", too late
> > to abort copy_process().
>
> You are right that freeing the partial utask is not enough.

Hmm. It is not that I think "it is not enough", I think this is pointless
whatever we do. Please see below.

But you know what? I am afraid I am totally confused again, this happens
more and more often. So please correct me.

> Would it make sense to keep the cleanup

But again, why do you think it makes any sense to keep the cleanup
you propose?

> and additionally send
> SIGKILL to the new child when the  uprobe state copy fails?

Or SIGILL like the rest of uprobes.c does...

Yes, this is what I meant. But this is only the first step to cleanup
this logic. I'll try to write another email tomorrow.

Lets suppose we change uprobe_copy_process() to kill the child. Then
why do we need to call uprobe_free_utask() in dup_utask() or do anything
else in copy_process() paths?

The child won't return to userspace, it will exit and call uprobe_free_utask()
itself.

> Also, should the existing "dup xol area" failure path be handled
> the same way?

Yes sure. But perhaps needs another discussion.

Oleg.