If the credential on an incoming thread is correct, don't bother

reaquiring it. In the same vein, don't bother dropping the thread cred
when goinf ot userland. We are guaranteed to nned it when we come back,
(which we are guaranteed to do).

Reviewed by:	jhb@freebsd.org, bde@freebsd.org (slightly different version)

1 files changed, 21 insertions, 0 deletions

diff --git a/sys/kern/kern_prot.c b/sys/kern/kern_prot.c
index 4214cc1..f7056a0 100644
--- a/sys/kern/kern_prot.c
+++ b/sys/kern/kern_prot.c
@@ -1684,6 +1684,27 @@ crdup(cr)
 }
 
 /*
+ * small routine to swap a thread's current ucred for the correct one
+ * taken from the process.
+ */
+void
+cred_update_thread(struct thread *td)
+{
+	struct proc *p;
+
+	p = td->td_proc;
+	if (td->td_ucred != NULL) {
+		mtx_lock(&Giant);
+		crfree(td->td_ucred);
+		mtx_unlock(&Giant);
+		td->td_ucred = NULL;
+	}
+	PROC_LOCK(p);
+	td->td_ucred = crhold(p->p_ucred);
+	PROC_UNLOCK(p);
+}
+
+/*
  * Get login name, if available.
  */
 #ifndef _SYS_SYSPROTO_H_