af_netlink: force credentials passing [CVE-2012-3520]
authorEric Dumazet <edumazet@google.com>
Tue, 21 Aug 2012 06:21:17 +0000 (06:21 +0000)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Tue, 2 Oct 2012 17:29:37 +0000 (10:29 -0700)
commit7c799a1e1ca2bc766574078b684c14474da9f704
tree3920b2c94d08c9355c0f6f3e94b30f8ffd42529b
parent9e296becde8a8da5bcc1a8e22f27bdf9bd8636fe
af_netlink: force credentials passing [CVE-2012-3520]

[ Upstream commit e0e3cea46d31d23dc40df0a49a7a2c04fe8edfea ]

Pablo Neira Ayuso discovered that avahi and
potentially NetworkManager accept spoofed Netlink messages because of a
kernel bug.  The kernel passes all-zero SCM_CREDENTIALS ancillary data
to the receiver if the sender did not provide such data, instead of not
including any such data at all or including the correct data from the
peer (as it is the case with AF_UNIX).

This bug was introduced in commit 16e572626961
(af_unix: dont send SCM_CREDENTIALS by default)

This patch forces passing credentials for netlink, as
before the regression.

Another fix would be to not add SCM_CREDENTIALS in
netlink messages if not provided by the sender, but it
might break some programs.

With help from Florian Weimer & Petr Matousek

This issue is designated as CVE-2012-3520

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Petr Matousek <pmatouse@redhat.com>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
include/net/scm.h
net/netlink/af_netlink.c
net/unix/af_unix.c