From: Xin Long <>
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 <>
> Signed-off-by: Xin Long <>

Applied and queued up for -stable, thank you.

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