linux-kernel - [PATCH 03/12] pid: get ppid pid_t of task in init_pid

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Date:	Tue, 20 Aug 2013 17:31:55 -0400
From:	Richard Guy Briggs <rgb@...hat.com>
To:	linux-audit@...hat.com, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org
Cc:	Richard Guy Briggs <rgb@...hat.com>,
	Eric Paris <eparis@...hat.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	John Johansen <john.johansen@...onical.com>,
	James Morris <james.l.morris@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Kentaro Takeda <takedakn@...data.co.jp>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 03/12] pid: get ppid pid_t of task in init_pid_ns safely

Added the functions
        task_ppid()
        task_ppid_nr_ns()
        task_ppid_nr_init_ns()
to safely abstract the lookup of the PPID (real_parent's tgid) of a process,
including rcu locking, in any required pid namespace.  This provides an
alternative to sys_getppid(), which is relative to the child process' pid
namespace.

(informed by ebiederman's 6c621b7e)
Cc: stable@...r.kernel.org
Cc: Eric W. Biederman <ebiederm@...ssion.com>
Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
---
 include/linux/sched.h |   23 +++++++++++++++++++++++
 1 files changed, 23 insertions(+), 0 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index d722490..ec04090 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1448,6 +1448,11 @@ static inline struct pid *task_session(struct task_struct *task)
 	return task->group_leader->pids[PIDTYPE_SID].pid;
 }
 
+static inline struct pid *task_ppid(struct task_struct *task)
+{
+	return task_tgid(rcu_dereference(current->real_parent));
+}
+
 struct pid_namespace;
 
 /*
@@ -1496,6 +1501,24 @@ static inline pid_t task_tgid_vnr(struct task_struct *tsk)
 }
 
 
+static inline pid_t task_ppid_nr_ns(struct task_struct *tsk,
+					struct pid_namespace *ns)
+{
+	pid_t pid;
+
+	rcu_read_lock();
+	pid = pid_nr_ns(task_ppid(current), ns);
+	rcu_read_unlock();
+
+	return pid;
+}
+
+static inline pid_t task_ppid_nr_init_ns(struct task_struct *tsk)
+{
+	return task_ppid_nr_ns(tsk, &init_pid_ns);
+}
+
+
 static inline pid_t task_pgrp_nr_ns(struct task_struct *tsk,
 					struct pid_namespace *ns)
 {
-- 
1.7.1

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