Commit 8515ae38 authored Aug 10, 2017 by Florian Westphal Committed by David S. Miller Aug 10, 2017

rtnetlink: switch rtnl_link_get_slave_info_data_size to rcu



David Ahern reports following splat:
 RTNL: assertion failed at net/core/dev.c (5717)
 netdev_master_upper_dev_get+0x5f/0x70
 if_nlmsg_size+0x158/0x240
 rtnl_calcit.isra.26+0xa3/0xf0

rtnl_link_get_slave_info_data_size currently assumes RTNL protection, but
there appears to be no hard requirement for this, so use rcu instead.

At the time of this writing, there are three 'get_slave_size' callbacks
(now invoked under rcu): bond_get_slave_size, vrf_get_slave_size and
br_port_get_slave_size, all return constant only (i.e. they don't sleep).

Fixes: 6853dd48 ("rtnetlink: protect handler table with rcu")
Reported-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 5c2bb9b6

net/core/rtnetlink.c

+12 −4

Original line number	Diff line number	Diff line
		@@ -402,16 +402,24 @@ static size_t rtnl_link_get_slave_info_data_size(const struct net_device *dev)
		{
		struct net_device *master_dev;
		const struct rtnl_link_ops *ops;
		size_t size = 0;

		master_dev = netdev_master_upper_dev_get((struct net_device *) dev);
		rcu_read_lock();

		master_dev = netdev_master_upper_dev_get_rcu((struct net_device *)dev);
		if (!master_dev)
		return 0;
		goto out;

		ops = master_dev->rtnl_link_ops;
		if (!ops \|\| !ops->get_slave_size)
		return 0;
		goto out;
		/* IFLA_INFO_SLAVE_DATA + nested data */
		return nla_total_size(sizeof(struct nlattr)) +
		size = nla_total_size(sizeof(struct nlattr)) +
		ops->get_slave_size(master_dev, dev);

		out:
		rcu_read_unlock();
		return size;
		}

		static size_t rtnl_link_get_size(const struct net_device *dev)

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