o Add a comment to exec_check_permissions() to indicate that the

passed vnode must be locked; this is the case because of calls
  to VOP_GETATTR(), VOP_ACCESS(), and VOP_OPEN().  This becomes
  more of an issue when VOP_ACCESS() gets a bit more complicated,
  which it does when you introduce ACL, Capability, and MAC
  support.

Obtained from:	TrustedBSD Project

sys/kern/kern_exec.c

@@ -708,6 +708,7 @@ exec_copyout_strings(imgp)
 
 /*
  * Check permissions of file to execute.
+ *	Called with imgp->vp locked.
  *	Return 0 for success or error code on failure.
  */
 int