nbd - security update

Tuomas Räsänen discovered that unsafe signal handling in nbd-server, the
server for the Network Block Device protocol, could allow remote
attackers to cause a deadlock in the server process and thus a denial of
service.

Tuomas Räsänen also discovered that the modern-style negotiation was
carried out in the main server process before forking the actual client
handler. This could allow a remote attacker to cause a denial of service
(crash) by querying a non-existent export. This issue only affected the
oldstable distribution (wheezy).

For the oldstable distribution (wheezy), these problems have been fixed
in version 1:3.2-4~deb7u5.

For the stable distribution (jessie), these problems have been fixed in
version 1:3.8-4+deb8u1.

For the testing distribution (stretch), these problems have been fixed
in version 1:3.10-1.

For the unstable distribution (sid), these problems have been fixed in
version 1:3.10-1.

We recommend that you upgrade your nbd packages.