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

[Oleg Nesterov]

On 08/24, Andrii Nakryiko wrote:
>
> On Mon, Aug 24, 2026 at 8:57 AM Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
> >
> > force_exit_sig(SIGILL) can't be ignored too. But I am fine either way.
>
> Current SIGILL sending is already pretty bad behavior that bites us
> periodically, instead of doubling down on killing the user space
> process because something about installing uprobe goes wrong, let's
> think about a bit less destructive way to do this. Mark uprobe for a
> particular process as defunct or "detaching it", or something along
> those lines. But not just kill innocent processes.

Well. Yes, SIGILL sending acts as BUG_ON(), this is not nice and
probably we can improve the current code. And, just in case, as for
uprobe_copy_process() in particular I agree that Option B (make fork()
fail) is better.

But what, say, uprobe_handle_trampoline() can do if ->return_instances
is NULL? Either we have a kernel bug, or the probed task does something
wrong. In both cases it is better to kill the task with pr_warn() and
generate the core dump.

Oleg.