kernel: netfilter: null pointer dereference in nf_ct_frag6_reasm()

net/ipv6/netfilter/nfconntrackreasm.c in the Linux kernel before 2.6.34, when the nfconntrackipv6 module is enabled, allows remote attackers to cause a denial of service NULL pointer dereference and system crash via certain types of fragmented IPv6 packets...