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

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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: ba7d49b1f0 ("rtnetlink: provide api for getting and setting slave info")
Signed-off-by: Eric 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: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2022-01-31 17:21:06 -08:00 committed by Jakub Kicinski
parent 04c2a47ffb
commit c6f6f2444b
1 changed files with 4 additions and 2 deletions
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6
net/core/rtnetlink.c
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@ -3275,8 +3275,8 @@ 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];
@ -3314,6 +3314,8 @@ replay:
else
dev = NULL;
master_dev = NULL;
m_ops = NULL;
if (dev) {
master_dev = netdev_master_upper_dev_get(dev);
if (master_dev)