proc connector: reject unprivileged listener bumps

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@chromium.org>
Cc: Evgeniy Polyakov <zbr@ioremap.net>
Cc: Matt Helsley <matthltc@us.ibm.com>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Acked-by: Matt Helsley <matthltc@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Qiang Huang <h.huangqiang@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c
index ff18e41f5b2272e06cb680cc8bc6628ccb48d80f..094a7107301d0ddb56fd6ac8e4522f5f398534a3 100644 (file)
--- a/drivers/connector/cn_proc.c
+++ b/drivers/connector/cn_proc.c
@@ -331,6 +331,12 @@ static void cn_proc_mcast_ctl(struct cn_msg *msg,
        if (msg->len != sizeof(*mc_op))
                return;
 
+       /* 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:
@@ -343,6 +349,8 @@ static void cn_proc_mcast_ctl(struct cn_msg *msg,
                err = EINVAL;
                break;
        }
+
+out:
        cn_proc_ack(err, msg->seq, msg->ack);
 }