Re: [PATCH] netfilter: ipset: Fix serious failure in CIDR tracking

[Oliver <oliver@8.c.9.b.0.7.4.0.1.0.0.2.ip6.arpa>]

On Tuesday 10 September 2013 23:55:14 Jozsef Kadlecsik wrote:
> On Tue, 10 Sep 2013, Oliver wrote:
> > From: Oliver Smith <oliver@8.c.9.b.0.7.4.0.1.0.0.2.ip6.arpa>
> > 
> > This fixes a serious bug affecting all hash types with a net element -
> > specifically, if a CIDR value is deleted such that none of the same size
> > exist any more, all larger (less-specific) values will then fail to
> > match. Adding back any prefix with a CIDR equal to or more specific than
> > the one deleted will fix it.
> > 
> > Steps to reproduce:
> > ipset -N test hash:net
> > ipset -A test 1.1.0.0/16
> > ipset -A test 2.2.2.0/24
> > ipset -T test 1.1.1.1		#1.1.1.1 IS in set
> > ipset -D test 2.2.2.0/24
> > ipset -T test 1.1.1.1		#1.1.1.1 IS NOT in set
> > 
> > This is due to the fact that the nets counter was unconditionally
> > decremented prior to the iteration that shifts up the entries. Now, we
> > first check if there is a proceeding entry and if not, decrement it and
> > return. Otherwise, we proceed to iterate and then clean up the last
> > element afterwards.
> > 
> > Signed-off-by: Oliver Smith <oliver@8.c.9.b.0.7.4.0.1.0.0.2.ip6.arpa>
> 
> Good catch! But unconditionally checking the next entry may point over the
> array.

Are you sure? In mtype_del_cidr() we only iterate up to (nets_length - 1) 
rather than nets_length, so I didn't think that i+1 could end up going over 
the end of the array.

Kind Regards,
Oliver.