This is a note to let you know that I've just added the patch titled bridge: check brport attr show in brport_show to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: bridge-check-brport-attr-show-in-brport_show.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Thu Mar 8 10:22:29 PST 2018 From: Xin Long <lucien.xin@xxxxxxxxx> Date: Mon, 12 Feb 2018 17:15:40 +0800 Subject: bridge: check brport attr show in brport_show From: Xin Long <lucien.xin@xxxxxxxxx> [ Upstream commit 1b12580af1d0677c3c3a19e35bfe5d59b03f737f ] 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 <xzhou@xxxxxxxxxx> Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/bridge/br_sysfs_if.c | 3 +++ 1 file changed, 3 insertions(+) --- a/net/bridge/br_sysfs_if.c +++ b/net/bridge/br_sysfs_if.c @@ -229,6 +229,9 @@ static ssize_t brport_show(struct kobjec 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); } Patches currently in stable-queue which might be from lucien.xin@xxxxxxxxx are queue-4.4/bridge-check-brport-attr-show-in-brport_show.patch