From: Oleg Nesterov Date: Fri, 29 Jul 2011 01:26:32 +0000 (-0700) Subject: proc_fork_connector: a lockless ->real_parent usage is not safe X-Git-Tag: v3.1-rc1~24^2~34 X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=9e8f90dfe58eb19140bc66655170c7aef9eadbf2;ds=sidebyside proc_fork_connector: a lockless ->real_parent usage is not safe 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 Cc: Vladimir Zapolskiy Cc: "David S. Miller" Cc: Evgeniy Polyakov Cc: Evgeniy Polyakov Signed-off-by: Andrew Morton Signed-off-by: David S. Miller --- diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c index 3ee1fdb31ea7..e55814bc0d06 100644 --- a/drivers/connector/cn_proc.c +++ b/drivers/connector/cn_proc.c @@ -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;