Commit 4c13e689 authored by Xin Long's avatar Xin Long Committed by Greg Kroah-Hartman

bridge: check brport attr show in brport_show

[ Upstream commit 1b12580a ]

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

Fixes: 9cf63747 ("bridge: add sysfs hook to flush forwarding table")
Reported-by: default avatarXiong Zhou <>
Signed-off-by: default avatarXin Long <>
Signed-off-by: default avatarDavid S. Miller <>
Signed-off-by: default avatarGreg Kroah-Hartman <>
parent 71978491
......@@ -235,6 +235,9 @@ 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);
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