From: Xin Long <lucien....@gmail.com>
Date: Mon, 12 Feb 2018 17:15:40 +0800
> 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 <xz...@redhat.com>
> Signed-off-by: Xin Long <lucien....@gmail.com>
Applied and queued up for -stable, thank you.
