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Commit bd43771e authored by Eric Dumazet's avatar Eric Dumazet Committed by Greg Kroah-Hartman
Browse files

rtnetlink: make sure to refresh master_dev/m_ops in __rtnl_newlink() 



commit c6f6f2444bdbe0079e41914a35081530d0409963 upstream.

While looking at one unrelated syzbot bug, I found the replay logic
in __rtnl_newlink() to potentially trigger use-after-free.

It is better to clear master_dev and m_ops inside the loop,
in case we have to replay it.

Fixes: ba7d49b1 ("rtnetlink: provide api for getting and setting slave info")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Jiri Pirko <jiri@nvidia.com>
Link: https://lore.kernel.org/r/20220201012106.216495-1-eric.dumazet@gmail.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent b1d17e92

net/core/rtnetlink.c

+4 −2
Original line number Diff line number Diff line
@@ -3022,8 +3022,8 @@ static int __rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh, 
	struct nlattr *slave_attr[RTNL_SLAVE_MAX_TYPE + 1];

	unsigned char name_assign_type = NET_NAME_USER;

	struct nlattr *linkinfo[IFLA_INFO_MAX + 1];

	const struct rtnl_link_ops *m_ops = NULL;

	struct net_device *master_dev = NULL;

	const struct rtnl_link_ops *m_ops;

	struct net_device *master_dev;

	struct net *net = sock_net(skb->sk);

	const struct rtnl_link_ops *ops;

	struct nlattr *tb[IFLA_MAX + 1];
@@ -3063,6 +3063,8 @@ static int __rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh, 
			dev = NULL;

	}



	master_dev = NULL;

	m_ops = NULL;

	if (dev) {

		master_dev = netdev_master_upper_dev_get(dev);

		if (master_dev)