glibc -- getaddrinfo stack-based buffer overflow

Fabio Olive Leite reports:

A stack-based buffer overflow was found in libresolv when invoked
from nss_dns, allowing specially crafted DNS responses to seize
control of EIP in the DNS client. The buffer overflow occurs in the
functions send_dg (send datagram) and send_vc (send TCP) for the
NSS module libnss_dns.so.2 when calling getaddrinfo with AF_UNSPEC
family, or in some cases AF_INET6 family. The use of AF_UNSPEC (or
AF_INET6 in some cases) triggers the low-level resolver code to
send out two parallel queries for A and AAAA. A mismanagement of
the buffers used for those queries could result in the response of
a query writing beyond the alloca allocated buffer created by
__res_nquery.