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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: Oleg 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2009-04-02 16:58:38 -07:00 committed by Linus Torvalds
parent 2ae448efc8
commit 52ee2dfdd4
2 changed files with 36 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
include/linux/sched.h
View File

@ -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.

31
kernel/pid.c
View File

@ -452,11 +452,24 @@ 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);
pid_t nr = 0;
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);
}
rcu_read_unlock();
return nr;
}
EXPORT_SYMBOL(task_pid_nr_ns);
EXPORT_SYMBOL(__task_pid_nr_ns);
pid_t task_tgid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)
{
@ -464,18 +477,6 @@ pid_t task_tgid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)
}
EXPORT_SYMBOL(task_tgid_nr_ns);
pid_t task_pgrp_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)
{
return pid_nr_ns(task_pgrp(tsk), ns);
}
EXPORT_SYMBOL(task_pgrp_nr_ns);
pid_t task_session_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)
{
return pid_nr_ns(task_session(tsk), 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));