[Bug 420] New: Divide by zero (/proc/sys/net/ipv4/neigh/DEV/base_reachable_time)

["Martin J. Bligh" <mbligh@aracnet.com>]

http://bugme.osdl.org/show_bug.cgi?id=420

           Summary: Divide by zero
                    (/proc/sys/net/ipv4/neigh/DEV/base_reachable_time)
    Kernel Version: 2.4.20, 2.5.63
            Status: NEW
          Severity: normal
             Owner: davem@vger.kernel.org
         Submitter: usui_mi@ybb.ne.jp


Distribution:Debian GNU/Linux 3.0, Vine Linux 2.6
Hardware Environment:
Software Environment:
Problem Description:
  Divide by zero (/proc/sys/net/ipv4/neigh/DEV/base_reachable_time)
Steps to reproduce:
  I found the problem of neigh_rand_reach_time() in net/core/neighbour.c.
  This function called by neigh_periodic_timer() each 300 seconds, 
  and argument of neigh_periodic_timer() is p->base_reachable_time.
  base_reachable_time can set to 0 by below sequence.

    echo 0 > /proc/sys/net/ipv4/neigh/DEV/base_reachable_time

  But neigh_rand_reach_time() divide by its argument.

    unsigned long neigh_rand_reach_time(unsigned long base)
    {
	return (net_random() % base) + (base>>1);
    }