4.4-stable review patch. If anyone has any objections, please let me know.
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From: Xin Long lucien.xin@gmail.com
[ 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@redhat.com Signed-off-by: Xin Long lucien.xin@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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); }