On 04/10, Eric W. Biederman wrote:As long as the original parent is preserved for getppid(). There are programs out there which communicate between the parent and child with signals, and if the original parent dies, it undesirable to have the child getppid() and start sending signals to a program not expecting them. Invites undefined behavior.
I'm trying to remember what the story is now. There is a nasty
race somewhere with reparenting, a threaded parent setting SIGCHLD to
SIGIGN, and non-default signals that results in an zombie that no one
can wait for and reap. It requires being reparented twice to trigger.
reparent_thread:
...
/* If we'd notified the old parent about this child's death,
* also notify the new parent.
*/
if (!traced && p->exit_state == EXIT_ZOMBIE &&
p->exit_signal != -1 && thread_group_empty(p))
do_notify_parent(p, p->exit_signal);
We notified /sbin/init. If it ignores SIGCHLD, we should release the task.
We don't do this.
The best fix I believe is to cleanup the forget_original_parent/reparent_thread
interaction and factor out this "exit_state == EXIT_ZOMBIE && exit_signal == -1"
checks.