From: Oleg Nesterov <oleg@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
Pavel Emelyanov <xemul@openvz.org>,
Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>,
linux-kernel@vger.kernel.org
Subject: [PATCH 1/3] pids: document task_pgrp/task_session is not safe without tasklist/rcu
Date: Fri, 16 Jan 2009 06:55:13 +0100 [thread overview]
Message-ID: <20090116055513.GA28121@redhat.com> (raw)
Even if task == current, it is not safe to dereference the result of
task_pgrp/task_session. We can race with another thread which changes
the special pid via setpgid/setsid.
Document this. The next 2 patches give an example of the unsafe usage,
we have more bad users.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
--- CUR/include/linux/sched.h~SP_1_COMMENT 2009-01-12 23:07:48.000000000 +0100
+++ CUR/include/linux/sched.h 2009-01-16 02:13:50.000000000 +0100
@@ -1449,6 +1449,13 @@ static inline struct pid *task_tgid(stru
return task->group_leader->pids[PIDTYPE_PID].pid;
}
+/*
+ * Without tasklist or rcu lock it is not safe to dereference
+ * the result of task_pgrp/task_session even if task == current,
+ * we can race with another thread doing sys_setsid/sys_setpgid.
+ *
+ */
+
static inline struct pid *task_pgrp(struct task_struct *task)
{
return task->group_leader->pids[PIDTYPE_PGID].pid;
reply other threads:[~2009-01-16 5:57 UTC|newest]
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