On Wed, May 15, 2019 at 05:35:15PM +0200, Oleg Nesterov wrote:
On 05/15, Oleg Nesterov wrote:
On 05/15, Christian Brauner wrote:
+SYSCALL_DEFINE2(pidfd_open, pid_t, pid, unsigned int, flags)
+{
+ int fd, ret;
+ struct pid *p;
+ struct task_struct *tsk;
+
+ if (flags)
+ return -EINVAL;
+
+ if (pid <= 0)
+ return -EINVAL;
+
+ p = find_get_pid(pid);
+ if (!p)
+ return -ESRCH;
+
+ rcu_read_lock();
+ tsk = pid_task(p, PIDTYPE_PID);
You do not need find_get_pid() before rcu_lock and put_pid() at the end.
You can just do find_vpid() under rcu_read_lock().
Ah, sorry. Somehow I forgot you need to call pidfd_create(pid), you can't
do this under rcu_read_lock().
So I was wrong, you can't avoid get/put_pid.
Yeah, I haven't made any changes yet.
Christian
