Patch "bridge: check brport attr show in brport_show" has been added to the 4.14-stable tree

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 4.14-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-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Xin Long <[email protected]>
Date: Mon, 12 Feb 2018 17:15:40 +0800
Subject: bridge: check brport attr show in brport_show

From: Xin Long <[email protected]>

[ 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().

---
 net/bridge/br_sysfs_if.c |    3 +++
 1 file changed, 3 insertions(+)

@@ -235,6 +235,9 @@ 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 [email protected] are

queue-4.14/bridge-check-brport-attr-show-in-brport_show.patch queue-4.14/sctp-do-not-pr_err-for-the-duplicated-node-in-transport-rhlist.patch