FreeBSD -- IPv6 remote Denial-of-Service

Problem Description:

Due do a missing check in the code of m_pulldown(9) data returned may not be contiguous as requested by the caller.

Impact:

Extra checks in the IPv6 code catch the error condition and trigger a kernel panic leading to a remote DoS (denial-of-service) attack with certain Ethernet interfaces. At this point it is unknown if any other than the IPv6 code paths can trigger a similar condition.