> The parent can play with real_blocked or saved_sigmask to block all > signals except STOP and KILL, use TASK_INTERRUPTIBLE for wait, and > just return ERESTART each time it gets the signal (it should clear > child->vfork_done if fatal_signal_pending). Yes, perhaps. > We should also check PF_KTHREAD though, there are in kernel users > of CLONE_VFORK. There is only __call_usermodehelper, but yes. > > Bu the way that happens ordinarily is > > to get all the way back to user mode and reenter with a normal syscall. > > That doesn't touch the user stack itself, but it sure makes one nervous. > > me too. Especially because I do not really know how !x86 machines > implement this all. The only problem I know of off hand is ia64's TIF_RESTORE_RSE (an arch-specific ptrace detail). But yes, it would require a careful reading of all the arch code paths. > We should also verify that the exiting/stopping parent can never write > to its ->mm. For example, exit_mm() does put_user(tsk->clear_child_tid). > Fortunately we can rely on PF_SIGNALED flag in this case. Right. Thanks, Roland -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>