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proc_fork_connector: a lockless ->real_parent usage is not safe

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proc_fork_connector() uses ->real_parent lockless.  This is not safe if
copy_process() was called with CLONE_THREAD or CLONE_PARENT, in this case
the parent != current can go away at any moment.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Vladimir Zapolskiy <vzapolskiy@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Evgeniy Polyakov <zbr@ioremap.net>
Cc: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Oleg Nesterov 2011-07-28 18:26:32 -07:00 committed by David S. Miller
parent 177c27bf05
commit 9e8f90dfe5
1 changed files with 6 additions and 2 deletions
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8
drivers/connector/cn_proc.c
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@ -57,6 +57,7 @@ void proc_fork_connector(struct task_struct *task)
struct proc_event *ev;
__u8 buffer[CN_PROC_MSG_SIZE];
struct timespec ts;
struct task_struct *parent;
if (atomic_read(&proc_event_num_listeners) < 1)
return;
@ -67,8 +68,11 @@ void proc_fork_connector(struct task_struct *task)
ktime_get_ts(&ts); /* get high res monotonic timestamp */
put_unaligned(timespec_to_ns(&ts), (__u64 *)&ev->timestamp_ns);
ev->what = PROC_EVENT_FORK;
ev->event_data.fork.parent_pid = task->real_parent->pid;
ev->event_data.fork.parent_tgid = task->real_parent->tgid;
rcu_read_lock();
parent = rcu_dereference(task->real_parent);
ev->event_data.fork.parent_pid = parent->pid;
ev->event_data.fork.parent_tgid = parent->tgid;
rcu_read_unlock();
ev->event_data.fork.child_pid = task->pid;
ev->event_data.fork.child_tgid = task->tgid;