On Wed, May 15, 2019 at 04:38:58PM +0200, 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().
Will do.
+ if (!tsk)
+ ret = -ESRCH;
+ else if (unlikely(!thread_group_leader(tsk)))
+ ret = -EINVAL;
it seems that you can do a single check
tsk = pid_task(p, PIDTYPE_TGID);
if (!tsk)
ret = -ESRCH;
this even looks more correct if we race with exec changing the leader.
The logic here being that you can only reach the thread_group leader
from struct pid if PIDTYPE_PID == PIDTYPE_TGID for this struct pid?
Thanks, Oleg.
Christian
