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proc connector: reject unprivileged listener bumps

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>
Cc: stable@vger.kernel.org
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Acked-by: Matt Helsley <matthltc@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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commit e70ab977991964a5a7ad1182799451d067e62669 1 parent 114a6f8
@kees kees authored davem330 committed
Showing with 8 additions and 0 deletions.
  1. +8 −0 drivers/connector/cn_proc.c
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8 drivers/connector/cn_proc.c
@@ -313,6 +313,12 @@ static void cn_proc_mcast_ctl(struct cn_msg *msg,
(task_active_pid_ns(current) != &init_pid_ns))
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:
@@ -325,6 +331,8 @@ static void cn_proc_mcast_ctl(struct cn_msg *msg,
err = EINVAL;
break;
}
+
+out:
cn_proc_ack(err, msg->seq, msg->ack);
}
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