From c876ad7682155958d0c9c27afe9017925c230d64 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Fri, 21 Dec 2012 20:27:12 -0800 Subject: pidns: Stop pid allocation when init dies Oleg pointed out that in a pid namespace the sequence. - pid 1 becomes a zombie - setns(thepidns), fork,... - reaping pid 1. - The injected processes exiting. Can lead to processes attempting access their child reaper and instead following a stale pointer. That waitpid for init can return before all of the processes in the pid namespace have exited is also unfortunate. Avoid these problems by disabling the allocation of new pids in a pid namespace when init dies, instead of when the last process in a pid namespace is reaped. Pointed-out-by: Oleg Nesterov Reviewed-by: Oleg Nesterov Signed-off-by: "Eric W. Biederman" --- include/linux/pid.h | 1 + include/linux/pid_namespace.h | 4 +++- 2 files changed, 4 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/linux/pid.h b/include/linux/pid.h index b152d44fb18..2381c973d89 100644 --- a/include/linux/pid.h +++ b/include/linux/pid.h @@ -121,6 +121,7 @@ int next_pidmap(struct pid_namespace *pid_ns, unsigned int last); extern struct pid *alloc_pid(struct pid_namespace *ns); extern void free_pid(struct pid *pid); +extern void disable_pid_allocation(struct pid_namespace *ns); /* * ns_of_pid() returns the pid namespace in which the specified pid was diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h index bf285999273..215e5e3dda1 100644 --- a/include/linux/pid_namespace.h +++ b/include/linux/pid_namespace.h @@ -21,7 +21,7 @@ struct pid_namespace { struct kref kref; struct pidmap pidmap[PIDMAP_ENTRIES]; int last_pid; - int nr_hashed; + unsigned int nr_hashed; struct task_struct *child_reaper; struct kmem_cache *pid_cachep; unsigned int level; @@ -42,6 +42,8 @@ struct pid_namespace { extern struct pid_namespace init_pid_ns; +#define PIDNS_HASH_ADDING (1U << 31) + #ifdef CONFIG_PID_NS static inline struct pid_namespace *get_pid_ns(struct pid_namespace *ns) { -- cgit v1.2.3