pid: generalize task_active_pid_ns (61bce0f1) · Commits · 戴 / test

Currently task_active_pid_ns is not safe to call after a task becomes a zombie and exit_task_namespaces is called, as nsproxy becomes NULL. By reading the pid namespace from the pid of the task we can trivially solve this problem at the cost of one extra memory read in what should be the same cacheline as we read the namespace from. When moving things around I have made task_active_pid_ns out of line because keeping it in pid_namespace.h would require adding includes of pid.h and sched.h that I don't think we want. This change does make task_active_pid_ns unsafe to call during copy_process until we attach a pid on the task_struct which seems to be a reasonable trade off. Signed-off-by:

Eric W. Biederman <ebiederm@xmission.com> Signed-off-by:

Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Bastian Blank <bastian@waldi.eu.org> Cc: Pavel Emelyanov <xemul@openvz.org> Cc: Nadia Derbey <Nadia.Derbey@bull.net> Acked-by:

Serge Hallyn <serue@us.ibm.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

include/linux/pid_namespace.h

+1 −5

Original line number	Diff line number	Diff line
		@@ -79,11 +79,7 @@ static inline void zap_pid_ns_processes(struct pid_namespace *ns)
		}
		#endif /* CONFIG_PID_NS */

		static inline struct pid_namespace task_active_pid_ns(struct task_struct tsk)
		{
		return tsk->nsproxy->pid_ns;
		}

		extern struct pid_namespace task_active_pid_ns(struct task_struct tsk);
		void pidhash_init(void);
		void pidmap_init(void);

kernel/fork.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -1126,12 +1126,12 @@ static struct task_struct *copy_process(unsigned long clone_flags,

		if (pid != &init_struct_pid) {
		retval = -ENOMEM;
		pid = alloc_pid(task_active_pid_ns(p));
		pid = alloc_pid(p->nsproxy->pid_ns);
		if (!pid)
		goto bad_fork_cleanup_io;

		if (clone_flags & CLONE_NEWPID) {
		retval = pid_ns_prepare_proc(task_active_pid_ns(p));
		retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
		if (retval < 0)
		goto bad_fork_free_pid;
		}

kernel/pid.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -474,6 +474,12 @@ pid_t task_session_nr_ns(struct task_struct tsk, struct pid_namespace ns)
		}
		EXPORT_SYMBOL(task_session_nr_ns);

		struct pid_namespace task_active_pid_ns(struct task_struct tsk)
		{
		return ns_of_pid(task_pid(tsk));
		}
		EXPORT_SYMBOL_GPL(task_active_pid_ns);

		/*
		* Used by proc to find the first pid that is greater than or equal to nr.
		*

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