Re: [CHECKER] 56 potential lock/unlock bugs in 2.5.8

[Andi Kleen <ak@suse.de>]

Dawson Engler <engler@csl.Stanford.EDU> writes:

> [BUG]  recheck: seems unlikely, though it does seem that the path is valid.
> /u2/engler/mc/oses/linux/2.5.8/net/ipv6/tcp_ipv6.c:206:tcp_v6_get_port: ERROR:A_B:112:206:Did not reverse 'spin_lock' [COUNTER=spin_lock:112] [fit=3] [fit_fn=11] [fn_ex=2] [fn_counter=1] [ex=5619] [counter=272] [z = 1.34804760770983] [fn-z = -2.25170500701057]
> 		rover = tcp_port_rover;
> 		do {	rover++;
> 			if ((rover < low) || (rover > high))
> 				rover = low;
> 			head = &tcp_bhash[tcp_bhashfn(rover)];
> Start --->
> 			spin_lock(&head->lock);
> 

           } while (--remaining > 0);
                tcp_port_rover = rover;
                spin_unlock(&tcp_portalloc_lock);

                /* Exhausted local port range during search? */
                ret = 1;
                if (remaining <= 0)
                        goto fail;


the goto can only hit when the lock hasn't been taken, so not unlocking it
is correct. It just rechecks the loop end condition, but your tool probably
doesn't know that. The wonders of structured programming :-)


-Andi