bridge: check brport attr show in brport_show
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>
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@ -255,6 +255,9 @@ static ssize_t brport_show(struct kobject *kobj,
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struct brport_attribute *brport_attr = to_brport_attr(attr);
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struct net_bridge_port *p = to_brport(kobj);
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if (!brport_attr->show)
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return -EINVAL;
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return brport_attr->show(p, buf);
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}
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