Commit 1b12580a authored Feb 12, 2018 by Xin Long Committed by David S. Miller Feb 12, 2018

bridge: check brport attr show in brport_show



Now br_sysfs_if file flush doesn't have attr show. To read it will
cause kernel panic after users chmod u+r this file.

Xiong found this issue when running the commands:

  ip link add br0 type bridge
  ip link add type veth
  ip link set veth0 master br0
  chmod u+r /sys/devices/virtual/net/veth0/brport/flush
  timeout 3 cat /sys/devices/virtual/net/veth0/brport/flush

kernel crashed with NULL a pointer dereference call trace.

This patch is to fix it by return -EINVAL when brport_attr->show
is null, just the same as the check for brport_attr->store in
brport_store().

Fixes: 9cf63747 ("bridge: add sysfs hook to flush forwarding table")
Reported-by: Xiong Zhou <xzhou@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 7ac8ff95

net/bridge/br_sysfs_if.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -255,6 +255,9 @@ static ssize_t brport_show(struct kobject *kobj,
		struct brport_attribute *brport_attr = to_brport_attr(attr);
		struct net_bridge_port *p = to_brport(kobj);

		if (!brport_attr->show)
		return -EINVAL;

		return brport_attr->show(p, buf);
		}