path: root/kernel/pid.c
diff options
authorOleg Nesterov <>2013-07-03 15:08:31 -0700
committerLinus Torvalds <>2013-07-03 16:08:03 -0700
commit8190773985141f063e1d6dc10200527c655abfb5 (patch)
tree5c148834f047748dfa2ce3500236b89656976567 /kernel/pid.c
parent80628ca06c5d42929de6bc22c0a41589a834d151 (diff)
kernel/fork.c:copy_process(): don't add the uninitialized child to thread/task/pid lists
copy_process() adds the new child to thread_group/init_task.tasks list and then does attach_pid(child, PIDTYPE_PID). This means that the lockless next_thread() or next_task() can see this thread with the wrong pid. Say, "ls /proc/pid/task" can list the same inode twice. We could move attach_pid(child, PIDTYPE_PID) up, but in this case find_task_by_vpid() can find the new thread before it was fully initialized. And this is already true for PIDTYPE_PGID/PIDTYPE_SID, With this patch copy_process() initializes child->pids[*].pid first, then calls attach_pid() to insert the task into the pid->tasks list. attach_pid() no longer need the "struct pid*" argument, it is always called after pid_link->pid was already set. Signed-off-by: Oleg Nesterov <> Cc: "Eric W. Biederman" <> Cc: Michal Hocko <> Cc: Pavel Emelyanov <> Cc: Sergey Dyasly <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'kernel/pid.c')
1 files changed, 4 insertions, 8 deletions
diff --git a/kernel/pid.c b/kernel/pid.c
index 0db3e791a06d..61980cefb1f5 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -373,14 +373,10 @@ EXPORT_SYMBOL_GPL(find_vpid);
* attach_pid() must be called with the tasklist_lock write-held.
-void attach_pid(struct task_struct *task, enum pid_type type,
- struct pid *pid)
+void attach_pid(struct task_struct *task, enum pid_type type)
- struct pid_link *link;
- link = &task->pids[type];
- link->pid = pid;
- hlist_add_head_rcu(&link->node, &pid->tasks[type]);
+ struct pid_link *link = &task->pids[type];
+ hlist_add_head_rcu(&link->node, &link->pid->tasks[type]);
static void __change_pid(struct task_struct *task, enum pid_type type,
@@ -412,7 +408,7 @@ void change_pid(struct task_struct *task, enum pid_type type,
struct pid *pid)
__change_pid(task, type, pid);
- attach_pid(task, type, pid);
+ attach_pid(task, type);
/* transfer_pid is an optimization of attach_pid(new), detach_pid(old) */