diff options
| -rw-r--r-- | include/linux/pid.h | 1 | ||||
| -rw-r--r-- | kernel/exit.c | 27 | ||||
| -rw-r--r-- | kernel/pid.c | 38 |
3 files changed, 65 insertions, 1 deletions
diff --git a/include/linux/pid.h b/include/linux/pid.h index 0dc940f..16644cc 100644 --- a/include/linux/pid.h +++ b/include/linux/pid.h @@ -125,6 +125,7 @@ extern struct pid *find_ge_pid(int nr, struct pid_namespace *); extern struct pid *alloc_pid(struct pid_namespace *ns); extern void FASTCALL(free_pid(struct pid *pid)); +extern void zap_pid_ns_processes(struct pid_namespace *pid_ns); /* * the helpers to get the pid's id seen from different namespaces diff --git a/kernel/exit.c b/kernel/exit.c index d9e8e5e..567909f 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -879,7 +879,32 @@ static inline void exit_child_reaper(struct task_struct *tsk) if (likely(tsk->group_leader != task_child_reaper(tsk))) return; - panic("Attempted to kill init!"); + if (tsk->nsproxy->pid_ns == &init_pid_ns) + panic("Attempted to kill init!"); + + /* + * @tsk is the last thread in the 'cgroup-init' and is exiting. + * Terminate all remaining processes in the namespace and reap them + * before exiting @tsk. + * + * Note that @tsk (last thread of cgroup-init) may not necessarily + * be the child-reaper (i.e main thread of cgroup-init) of the + * namespace i.e the child_reaper may have already exited. + * + * Even after a child_reaper exits, we let it inherit orphaned children, + * because, pid_ns->child_reaper remains valid as long as there is + * at least one living sub-thread in the cgroup init. + + * This living sub-thread of the cgroup-init will be notified when + * a child inherited by the 'child-reaper' exits (do_notify_parent() + * uses __group_send_sig_info()). Further, when reaping child processes, + * do_wait() iterates over children of all living sub threads. + + * i.e even though 'child_reaper' thread is listed as the parent of the + * orphaned children, any living sub-thread in the cgroup-init can + * perform the role of the child_reaper. + */ + zap_pid_ns_processes(tsk->nsproxy->pid_ns); } fastcall NORET_TYPE void do_exit(long code) diff --git a/kernel/pid.c b/kernel/pid.c index d88b83e..b3e6d7c 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -34,6 +34,7 @@ #include <linux/hash.h> #include <linux/pid_namespace.h> #include <linux/init_task.h> +#include <linux/syscalls.h> #define pid_hashfn(nr, ns) \ hash_long((unsigned long)nr + (unsigned long)ns, pidhash_shift) @@ -567,6 +568,43 @@ void free_pid_ns(struct kref *kref) put_pid_ns(parent); } +void zap_pid_ns_processes(struct pid_namespace *pid_ns) +{ + int nr; + int rc; + + /* + * The last thread in the cgroup-init thread group is terminating. + * Find remaining pid_ts in the namespace, signal and wait for them + * to exit. + * + * Note: This signals each threads in the namespace - even those that + * belong to the same thread group, To avoid this, we would have + * to walk the entire tasklist looking a processes in this + * namespace, but that could be unnecessarily expensive if the + * pid namespace has just a few processes. Or we need to + * maintain a tasklist for each pid namespace. + * + */ + read_lock(&tasklist_lock); + nr = next_pidmap(pid_ns, 1); + while (nr > 0) { + kill_proc_info(SIGKILL, SEND_SIG_PRIV, nr); + nr = next_pidmap(pid_ns, nr); + } + read_unlock(&tasklist_lock); + + do { + clear_thread_flag(TIF_SIGPENDING); + rc = sys_wait4(-1, NULL, __WALL, NULL); + } while (rc != -ECHILD); + + + /* Child reaper for the pid namespace is going away */ + pid_ns->child_reaper = NULL; + return; +} + /* * The pid hash table is scaled according to the amount of memory in the * machine. From a minimum of 16 slots up to 4096 slots at one gigabyte or |
