diff options
| -rw-r--r-- | include/linux/prctl.h | 3 | ||||
| -rw-r--r-- | include/linux/sched.h | 12 | ||||
| -rw-r--r-- | kernel/exit.c | 33 | ||||
| -rw-r--r-- | kernel/fork.c | 3 | ||||
| -rw-r--r-- | kernel/sys.c | 8 |
5 files changed, 54 insertions, 5 deletions
diff --git a/include/linux/prctl.h b/include/linux/prctl.h index a0413ac..e0cfec2 100644 --- a/include/linux/prctl.h +++ b/include/linux/prctl.h @@ -121,4 +121,7 @@ #define PR_SET_PTRACER 0x59616d61 # define PR_SET_PTRACER_ANY ((unsigned long)-1) +#define PR_SET_CHILD_SUBREAPER 36 +#define PR_GET_CHILD_SUBREAPER 37 + #endif /* _LINUX_PRCTL_H */ diff --git a/include/linux/sched.h b/include/linux/sched.h index 0c147a4..0c3854b 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -553,6 +553,18 @@ struct signal_struct { int group_stop_count; unsigned int flags; /* see SIGNAL_* flags below */ + /* + * PR_SET_CHILD_SUBREAPER marks a process, like a service + * manager, to re-parent orphan (double-forking) child processes + * to this process instead of 'init'. The service manager is + * able to receive SIGCHLD signals and is able to investigate + * the process until it calls wait(). All children of this + * process will inherit a flag if they should look for a + * child_subreaper process at exit. + */ + unsigned int is_child_subreaper:1; + unsigned int has_child_subreaper:1; + /* POSIX.1b Interval Timers */ struct list_head posix_timers; diff --git a/kernel/exit.c b/kernel/exit.c index 16b07bf..456329f 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -687,11 +687,11 @@ static void exit_mm(struct task_struct * tsk) } /* - * When we die, we re-parent all our children. - * Try to give them to another thread in our thread - * group, and if no such member exists, give it to - * the child reaper process (ie "init") in our pid - * space. + * When we die, we re-parent all our children, and try to: + * 1. give them to another thread in our thread group, if such a member exists + * 2. give it to the first ancestor process which prctl'd itself as a + * child_subreaper for its children (like a service manager) + * 3. give it to the init process (PID 1) in our pid namespace */ static struct task_struct *find_new_reaper(struct task_struct *father) __releases(&tasklist_lock) @@ -722,6 +722,29 @@ static struct task_struct *find_new_reaper(struct task_struct *father) * forget_original_parent() must move them somewhere. */ pid_ns->child_reaper = init_pid_ns.child_reaper; + } else if (father->signal->has_child_subreaper) { + struct task_struct *reaper; + + /* + * Find the first ancestor marked as child_subreaper. + * Note that the code below checks same_thread_group(reaper, + * pid_ns->child_reaper). This is what we need to DTRT in a + * PID namespace. However we still need the check above, see + * http://marc.info/?l=linux-kernel&m=131385460420380 + */ + for (reaper = father->real_parent; + reaper != &init_task; + reaper = reaper->real_parent) { + if (same_thread_group(reaper, pid_ns->child_reaper)) + break; + if (!reaper->signal->is_child_subreaper) + continue; + thread = reaper; + do { + if (!(thread->flags & PF_EXITING)) + return reaper; + } while_each_thread(reaper, thread); + } } return pid_ns->child_reaper; diff --git a/kernel/fork.c b/kernel/fork.c index 37674ec..b9372a0 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1051,6 +1051,9 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) sig->oom_score_adj = current->signal->oom_score_adj; sig->oom_score_adj_min = current->signal->oom_score_adj_min; + sig->has_child_subreaper = current->signal->has_child_subreaper || + current->signal->is_child_subreaper; + mutex_init(&sig->cred_guard_mutex); return 0; diff --git a/kernel/sys.c b/kernel/sys.c index 888d227..9eb7fca 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -1962,6 +1962,14 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, case PR_SET_MM: error = prctl_set_mm(arg2, arg3, arg4, arg5); break; + case PR_SET_CHILD_SUBREAPER: + me->signal->is_child_subreaper = !!arg2; + error = 0; + break; + case PR_GET_CHILD_SUBREAPER: + error = put_user(me->signal->is_child_subreaper, + (int __user *) arg2); + break; default: error = -EINVAL; break; |
