On Wed, Jul 24, 2019 at 4:48 PM Christian Brauner <christian@xxxxxxxxxx> wrote: > If CLONE_WAIT_PID is set the newly created process will not be > considered by process wait requests that wait generically on children > such as: > > syscall(__NR_wait4, -1, wstatus, options, rusage) > syscall(__NR_waitpid, -1, wstatus, options) > syscall(__NR_waitid, P_ALL, -1, siginfo, options, rusage) > syscall(__NR_waitid, P_PGID, -1, siginfo, options, rusage) > syscall(__NR_waitpid, -pid, wstatus, options) > syscall(__NR_wait4, -pid, wstatus, options, rusage) > > A process created with CLONE_WAIT_PID can only be waited upon with a > focussed wait call. This ensures that processes can be reaped even if > all file descriptors referring to it are closed. [...] > diff --git a/kernel/fork.c b/kernel/fork.c > index baaff6570517..a067f3876e2e 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -1910,6 +1910,8 @@ static __latent_entropy struct task_struct *copy_process( > delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ > p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE); > p->flags |= PF_FORKNOEXEC; > + if (clone_flags & CLONE_WAIT_PID) > + p->flags |= PF_WAIT_PID; > INIT_LIST_HEAD(&p->children); > INIT_LIST_HEAD(&p->sibling); > rcu_copy_process(p); This means that if a process with PF_WAIT_PID forks, the child inherits the flag, right? That seems unintended? You might have to add something like "if (clone_flags & CLONE_THREAD == 0) p->flags &= ~PF_WAIT_PID;" before this. (I think threads do have to inherit the flag so that the case where a non-leader thread of the child goes through execve and steals the leader's identity is handled properly.) Or you could cram it somewhere into signal_struct instead of on the task - that might be a more logical place for it?
