From e0e3cea46d31d23dc40df0a49a7a2c04fe8edfea Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 21 Aug 2012 06:21:17 +0000 Subject: [PATCH] af_netlink: force credentials passing [CVE-2012-3520] 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 Cc: Petr Matousek Cc: Florian Weimer Cc: Pablo Neira Ayuso Signed-off-by: David S. Miller --- include/net/scm.h | 4 +++- net/netlink/af_netlink.c | 2 +- net/unix/af_unix.c | 4 ++-- 3 files changed, 6 insertions(+), 4 deletions(-) diff --git a/include/net/scm.h b/include/net/scm.h index 079d7887dac1..7dc0854f0b38 100644 --- a/include/net/scm.h +++ b/include/net/scm.h @@ -70,9 +70,11 @@ static __inline__ void scm_destroy(struct scm_cookie *scm) } static __inline__ int scm_send(struct socket *sock, struct msghdr *msg, - struct scm_cookie *scm) + struct scm_cookie *scm, bool forcecreds) { memset(scm, 0, sizeof(*scm)); + if (forcecreds) + scm_set_cred(scm, task_tgid(current), current_cred()); unix_get_peersec_dgram(sock, scm); if (msg->msg_controllen <= 0) return 0; diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 5463969da45b..1445d73533ed 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -1362,7 +1362,7 @@ static int netlink_sendmsg(struct kiocb *kiocb, struct socket *sock, if (NULL == siocb->scm) siocb->scm = &scm; - err = scm_send(sock, msg, siocb->scm); + err = scm_send(sock, msg, siocb->scm, true); if (err < 0) return err; diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index e4768c180da2..c5ee4ff61364 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -1450,7 +1450,7 @@ static int unix_dgram_sendmsg(struct kiocb *kiocb, struct socket *sock, if (NULL == siocb->scm) siocb->scm = &tmp_scm; wait_for_unix_gc(); - err = scm_send(sock, msg, siocb->scm); + err = scm_send(sock, msg, siocb->scm, false); if (err < 0) return err; @@ -1619,7 +1619,7 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock, if (NULL == siocb->scm) siocb->scm = &tmp_scm; wait_for_unix_gc(); - err = scm_send(sock, msg, siocb->scm); + err = scm_send(sock, msg, siocb->scm, false); if (err < 0) return err; -- 2.34.1