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Message-Id: <20220204091912.593539145@linuxfoundation.org>
Date: Fri, 4 Feb 2022 10:20:21 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
Jiri Pirko <jiri@...dia.com>, Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH 5.4 08/10] rtnetlink: make sure to refresh master_dev/m_ops in __rtnl_newlink()
From: Eric Dumazet <edumazet@...gle.com>
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: ba7d49b1f0f8 ("rtnetlink: provide api for getting and setting slave info")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Jiri Pirko <jiri@...dia.com>
Link: https://lore.kernel.org/r/20220201012106.216495-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
net/core/rtnetlink.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -3022,8 +3022,8 @@ static int __rtnl_newlink(struct sk_buff
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 @@ replay:
dev = NULL;
}
+ master_dev = NULL;
+ m_ops = NULL;
if (dev) {
master_dev = netdev_master_upper_dev_get(dev);
if (master_dev)
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