[PATCH 1/5] pid: get pid_t ppid of task in init_pid_ns

Added the functions task_ppid_nr_ns() and task_ppid_nr() to abstract the lookup of the PPID (real_parent's pid_t) of a process, including rcu locking, in the arbitrary and init_pid_ns. This provides an alternative to sys_getppid(), which is relative to the child process' pid namespace. (informed by ebiederman's 6c621b7e) Cc: stable(a)vger.kernel.org Cc: Eric W. Biederman <ebiederm(a)xmission.com&gt; Signed-off-by: Richard Guy Briggs <rgb(a)redhat.com&gt; --- include/linux/sched.h | 18 ++++++++++++++++++ 1 files changed, 18 insertions(+), 0 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 53f97eb..685326f 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1561,6 +1561,24 @@ static inline pid_t task_tgid_vnr(struct task_struct *tsk) } +static int pid_alive(const struct task_struct *p); +static inline pid_t task_ppid_nr_ns(const struct task_struct *tsk, struct pid_namespace *ns) +{ + pid_t pid = 0; + + rcu_read_lock(); + if (pid_alive(tsk)) + pid = task_tgid_nr_ns(rcu_dereference(tsk->real_parent), ns); + rcu_read_unlock(); + + return pid; +} + +static inline pid_t task_ppid_nr(const struct task_struct *tsk) +{ + return task_ppid_nr_ns(tsk, &init_pid_ns); +} + static inline pid_t task_pgrp_nr_ns(struct task_struct *tsk, struct pid_namespace *ns) { -- 1.7.1