[PATCH 027/150] proc connector: reject unprivileged listener bumps

[Luis Henriques]

3.5.7.9 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Kees Cook <keescook at chromium.org>

commit e70ab977991964a5a7ad1182799451d067e62669 upstream.

While PROC_CN_MCAST_LISTEN/IGNORE is entirely advisory, it was possible
for an unprivileged user to turn off notifications for all listeners by
sending PROC_CN_MCAST_IGNORE. Instead, require the same privileges as
required for a multicast bind.

Signed-off-by: Kees Cook <keescook at chromium.org>
Cc: Evgeniy Polyakov <zbr at ioremap.net>
Cc: Matt Helsley <matthltc at us.ibm.com>
Acked-by: Evgeniy Polyakov <zbr at ioremap.net>
Acked-by: Matt Helsley <matthltc at us.ibm.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
[ luis: backported to 3.5 ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/connector/cn_proc.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c
index 77e1e6c..9d90e8c 100644
--- a/drivers/connector/cn_proc.c
+++ b/drivers/connector/cn_proc.c
@@ -303,7 +303,13 @@ static void cn_proc_mcast_ctl(struct cn_msg *msg,
 	if (msg->len != sizeof(*mc_op))
 		return;
 
-	mc_op = (enum proc_cn_mcast_op*)msg->data;
+	/* Can only change if privileged. */
+	if (!capable(CAP_NET_ADMIN)) {
+		err = EPERM;
+		goto out;
+	}
+
+	mc_op = (enum proc_cn_mcast_op *)msg->data;
 	switch (*mc_op) {
 	case PROC_CN_MCAST_LISTEN:
 		atomic_inc(&proc_event_num_listeners);
@@ -315,6 +321,8 @@ static void cn_proc_mcast_ctl(struct cn_msg *msg,
 		err = EINVAL;
 		break;
 	}
+
+out:
 	cn_proc_ack(err, msg->seq, msg->ack);
 }
 
-- 
1.8.1.2