Renew semaphore's pointer after wakeup since during msleep

sem_base may have been modified by destroying one of semaphores
and semptr would not be valid in this case.

PR: kern/123731

sys/kern/sysv_sem.c

@@ -1166,6 +1166,13 @@ semop(td, uap)
 			goto done2;
 		}
 
+		/*
+		 * Renew the semaphore's pointer after wakeup since
+		 * during msleep sem_base may have been modified and semptr
+		 * is not valid any more
+		 */
+		semptr = &semakptr->u.sem_base[sopptr->sem_num];
+
 		/*
 		 * The semaphore is still alive.  Readjust the count of
 		 * waiting processes.