From 1b12580af1d0677c3c3a19e35bfe5d59b03f737f Mon Sep 17 00:00:00 2001 From: Xin Long Date: Mon, 12 Feb 2018 17:15:40 +0800 Subject: [PATCH] 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: 9cf637473c85 ("bridge: add sysfs hook to flush forwarding table") Reported-by: Xiong Zhou Signed-off-by: Xin Long Signed-off-by: David S. Miller --- net/bridge/br_sysfs_if.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/bridge/br_sysfs_if.c b/net/bridge/br_sysfs_if.c index 0254c35b2bf0..126a8ea73c96 100644 --- a/net/bridge/br_sysfs_if.c +++ b/net/bridge/br_sysfs_if.c @@ -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); }