Oleg Nesterov <[email protected]> writes: > On 04/02, Eric W. Biederman wrote: >> >> --- a/kernel/fork.c >> +++ b/kernel/fork.c >> @@ -1515,6 +1515,13 @@ static __latent_entropy struct task_struct >> *copy_process( >> if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) >> return ERR_PTR(-EINVAL); >> >> + /* Disallow CLONE_THREAD with a shared SIGHAND structure. No >> + * one cares > > Well, can't resists... I won't argue, but we can't know if no one cares > or not. I agree that most probably this won't break something, but who > knows... I am always scared when we add the incompatible changes.
I agree that changing userspace semantics is something to be very careful with. But at least for purposes of discussion I think this is a good patch. I can avoid this change but it requires moving sighand->siglock into signal_struct and introducing a new spinlock into sighand_struct to just guard the signal handlers. However I think the change to move siglock would be a distraction from the larger issues of this patchset. Once we address the core issues I will be happy to revisit this. >> and supporting it leads to unnecessarily complex >> + * code. >> + */ >> + if ((clone_flags & CLONE_THREAD) && >> (atomic_read(¤t->sighand->count) > 1)) >> + return ERR_PTR(-EINVAL); > > Perhaps the comment should explain why we do this and say that > sighand-unsharing in de_thread() depends on this. That would be a better comment. Eric
