The patch titled
pids: refactor vnr/nr_ns helpers to make them safe
has been added to the -mm tree. Its filename is
pids-refactor-vnr-nr_ns-helpers-to-make-them-safe.patch
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------------------------------------------------------
Subject: pids: refactor vnr/nr_ns helpers to make them safe
From: Oleg Nesterov <oleg@xxxxxxxxxx>
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@xxxxxxxxxx>
Cc: Louis Rilling <Louis.Rilling@xxxxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxx>
Cc: Sukadev Bhattiprolu <sukadev@xxxxxxxxxxxxxxxxxx>
Cc: Roland McGrath <roland@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/sched.h | 27 ++++++++++++++++++++-------
kernel/pid.c | 31 ++++++++++++++++---------------
2 files changed, 36 insertions(+), 22 deletions(-)
diff -puN include/linux/sched.h~pids-refactor-vnr-nr_ns-helpers-to-make-them-safe include/linux/sched.h
--- a/include/linux/sched.h~pids-refactor-vnr-nr_ns-helpers-to-make-them-safe
+++ a/include/linux/sched.h
@@ -1479,17 +1479,23 @@ 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);
}
@@ -1511,11 +1517,15 @@ static inline pid_t task_pgrp_nr(struct
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);
}
@@ -1524,14 +1534,17 @@ static inline pid_t task_session_nr(stru
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.
diff -puN kernel/pid.c~pids-refactor-vnr-nr_ns-helpers-to-make-them-safe kernel/pid.c
--- a/kernel/pid.c~pids-refactor-vnr-nr_ns-helpers-to-make-them-safe
+++ a/kernel/pid.c
@@ -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
}
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));
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
getrusage-fill-ru_maxrss-value.patch
pids-document-task_pgrp-task_session-is-not-safe-without-tasklist-rcu.patch
pids-document-task_pgrp-task_session-is-not-safe-without-tasklist-rcu-fix.patch
pids-improve-get_task_pid-to-fix-the-unsafe-sys_wait4-task_pgrp.patch
pids-refactor-vnr-nr_ns-helpers-to-make-them-safe.patch
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