Fix leaking of kernel heap addresses in net/

This patch series resolves the leakage of kernel heap addresses to userspace via network protocol /proc interfaces. Revealing this information is a bad idea from a security perspective for a number of reasons, the most obvious of which is it provides unprivileged users a mechanism by which to create a structure in the kernel heap containing function pointers, obtain the address of that structure, and overwrite those function pointers by leveraging other vulnerabilities. It is my hope that by eliminating this information leakage, in conjunction with making statically-declared function pointer tables read-only (to be done in a separate patch series), we can at least add a small hurdle for the exploitation of a subset of kernel vulnerabilities.

To maintain compatibility with userspace programs relying on consistent /proc output, the output descriptions and number of fields are not changed. When a unique identifier for the socket is desired, the socket address has been replaced with the socket inode number. When the inode number is already present in the output, the address has been replaced with a 0. In these cases, the format specifier has been changed to %d, because a %p output of 0 from kernel space is written as "(null)", while userspace %p can only parse "(nil)".

To address feedback that this debugging information is often useful and should not be removed, the original kernel addresses are printed when the reader has CAP_NET_ADMIN. The result is not especially pretty, but I chose the more verbose option of providing separate print statements for each case rather than inserting conditionals into the print statements themselves, which would make for poor readability.

---
 net/atm/proc.c           |    2 +-
 net/can/bcm.c            |   17 +++--
 net/ipv4/raw.c           |   27 +++++--
 net/ipv4/tcp_ipv4.c      |  136 +++++++++++++++++++++++++-----------
 net/ipv4/udp.c           |   28 +++++--
 net/ipv6/tcp_ipv6.c      |  173 +++++++++++++++++++++++++++++++--------------
 net/key/af_key.c         |   27 +++++--
 net/netlink/af_netlink.c |   41 ++++++++---
 net/packet/af_packet.c   |   36 +++++++---
 net/phonet/socket.c      |   27 +++++--
 net/sctp/proc.c          |   56 +++++++++++----
 net/unix/af_unix.c       |   37 +++++++---
 12 files changed, 427 insertions(+), 180 deletions(-)