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Commit 52ee2dfd authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
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pids: refactor vnr/nr_ns helpers to make them safe 



Inho, the safety rules for vnr/nr_ns helpers are horrible and buggy.

task_pid_nr_ns(task) needs rcu/tasklist depending on task == current.

As for "special" pids, vnr/nr_ns helpers always need rcu.  However, if
task != current, they are unsafe even under rcu lock, we can't trust
task->group_leader without the special checks.

And almost every helper has a callsite which needs a fix.

Also, it is a bit annoying that the implementations of, say,
task_pgrp_vnr() and task_pgrp_nr_ns() are not "symmetrical".

This patch introduces the new helper, __task_pid_nr_ns(), which is always
safe to use, and turns all other helpers into the trivial wrappers.

After this I'll send another patch which converts task_tgid_xxx() as well,
they're are a bit special.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Cc: Louis Rilling <Louis.Rilling@kerlabs.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 2ae448ef

include/linux/sched.h

+20 −7
Original line number Diff line number Diff line
@@ -1519,17 +1519,23 @@ struct pid_namespace; 
 *

 * see also pid_nr() etc in include/linux/pid.h

 */

pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type,

			struct pid_namespace *ns);



static inline pid_t task_pid_nr(struct task_struct *tsk)

{

	return tsk->pid;

}



pid_t task_pid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns);

static inline pid_t task_pid_nr_ns(struct task_struct *tsk,

					struct pid_namespace *ns)

{

	return __task_pid_nr_ns(tsk, PIDTYPE_PID, ns);

}



static inline pid_t task_pid_vnr(struct task_struct *tsk)

{

	return pid_vnr(task_pid(tsk));

	return __task_pid_nr_ns(tsk, PIDTYPE_PID, NULL);

}
@@ -1551,11 +1557,15 @@ static inline pid_t task_pgrp_nr(struct task_struct *tsk) 
	return tsk->signal->__pgrp;

}



pid_t task_pgrp_nr_ns(struct task_struct *tsk, struct pid_namespace *ns);

static inline pid_t task_pgrp_nr_ns(struct task_struct *tsk,

					struct pid_namespace *ns)

{

	return __task_pid_nr_ns(tsk, PIDTYPE_PGID, ns);

}



static inline pid_t task_pgrp_vnr(struct task_struct *tsk)

{

	return pid_vnr(task_pgrp(tsk));

	return __task_pid_nr_ns(tsk, PIDTYPE_PGID, NULL);

}
@@ -1564,14 +1574,17 @@ static inline pid_t task_session_nr(struct task_struct *tsk) 
	return tsk->signal->__session;

}



pid_t task_session_nr_ns(struct task_struct *tsk, struct pid_namespace *ns);

static inline pid_t task_session_nr_ns(struct task_struct *tsk,

					struct pid_namespace *ns)

{

	return __task_pid_nr_ns(tsk, PIDTYPE_SID, ns);

}



static inline pid_t task_session_vnr(struct task_struct *tsk)

{

	return pid_vnr(task_session(tsk));

	return __task_pid_nr_ns(tsk, PIDTYPE_SID, NULL);

}





/**

 * pid_alive - check that a task structure is not stale

 * @p: Task structure to be checked.

kernel/pid.c

+16 −15
Original line number Diff line number Diff line
@@ -452,29 +452,30 @@ pid_t pid_vnr(struct pid *pid) 
}

EXPORT_SYMBOL_GPL(pid_vnr);



pid_t task_pid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)

pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type,

			struct pid_namespace *ns)

{

	return pid_nr_ns(task_pid(tsk), ns);

}

EXPORT_SYMBOL(task_pid_nr_ns);

	pid_t nr = 0;



pid_t task_tgid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)

{

	return pid_nr_ns(task_tgid(tsk), ns);

	rcu_read_lock();

	if (!ns)

		ns = current->nsproxy->pid_ns;

	if (likely(pid_alive(task))) {

		if (type != PIDTYPE_PID)

			task = task->group_leader;

		nr = pid_nr_ns(task->pids[type].pid, ns);

	}

EXPORT_SYMBOL(task_tgid_nr_ns);

	rcu_read_unlock();



pid_t task_pgrp_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)

{

	return pid_nr_ns(task_pgrp(tsk), ns);

	return nr;

}

EXPORT_SYMBOL(task_pgrp_nr_ns);

EXPORT_SYMBOL(__task_pid_nr_ns);



pid_t task_session_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)

pid_t task_tgid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)

{

	return pid_nr_ns(task_session(tsk), ns);

	return pid_nr_ns(task_tgid(tsk), ns);

}

EXPORT_SYMBOL(task_session_nr_ns);

EXPORT_SYMBOL(task_tgid_nr_ns);



struct pid_namespace *task_active_pid_ns(struct task_struct *tsk)

{