From: Cong Wang cong.wang@bytedance.com
[ Upstream commit a100243d95a60d74ae9bb9df1f5f2192e9aed6a7 ]
When we call af_ops->set_link_af() we hold a RCU read lock as we retrieve af_ops from the RCU protected list, but this is unnecessary because we already hold RTNL lock, which is the writer lock for protecting rtnl_af_ops, so it is safer than RCU read lock. Similar for af_ops->validate_link_af().
This was not a problem until we begin to take mutex lock down the path of ->set_link_af() in __ipv6_dev_mc_dec() recently. We can just drop the RCU read lock there and assert RTNL lock.
Reported-and-tested-by: syzbot+7d941e89dd48bcf42573@syzkaller.appspotmail.com Fixes: 63ed8de4be81 ("mld: add mc_lock for protecting per-interface mld data") Tested-by: Taehee Yoo ap420073@gmail.com Signed-off-by: Cong Wang cong.wang@bytedance.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/core/rtnetlink.c | 26 +++++++------------------- net/ipv4/devinet.c | 4 ++-- 2 files changed, 9 insertions(+), 21 deletions(-)
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index ec931b080156..c6e75bd0035d 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -543,7 +543,9 @@ static const struct rtnl_af_ops *rtnl_af_lookup(const int family) { const struct rtnl_af_ops *ops;
- list_for_each_entry_rcu(ops, &rtnl_af_ops, list) { + ASSERT_RTNL(); + + list_for_each_entry(ops, &rtnl_af_ops, list) { if (ops->family == family) return ops; } @@ -2274,27 +2276,18 @@ static int validate_linkmsg(struct net_device *dev, struct nlattr *tb[]) nla_for_each_nested(af, tb[IFLA_AF_SPEC], rem) { const struct rtnl_af_ops *af_ops;
- rcu_read_lock(); af_ops = rtnl_af_lookup(nla_type(af)); - if (!af_ops) { - rcu_read_unlock(); + if (!af_ops) return -EAFNOSUPPORT; - }
- if (!af_ops->set_link_af) { - rcu_read_unlock(); + if (!af_ops->set_link_af) return -EOPNOTSUPP; - }
if (af_ops->validate_link_af) { err = af_ops->validate_link_af(dev, af); - if (err < 0) { - rcu_read_unlock(); + if (err < 0) return err; - } } - - rcu_read_unlock(); } }
@@ -2868,17 +2861,12 @@ static int do_setlink(const struct sk_buff *skb, nla_for_each_nested(af, tb[IFLA_AF_SPEC], rem) { const struct rtnl_af_ops *af_ops;
- rcu_read_lock(); - BUG_ON(!(af_ops = rtnl_af_lookup(nla_type(af))));
err = af_ops->set_link_af(dev, af, extack); - if (err < 0) { - rcu_read_unlock(); + if (err < 0) goto errout; - }
- rcu_read_unlock(); status |= DO_SETLINK_NOTIFY; } } diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c index 1c6429c353a9..73721a4448bd 100644 --- a/net/ipv4/devinet.c +++ b/net/ipv4/devinet.c @@ -1955,7 +1955,7 @@ static int inet_validate_link_af(const struct net_device *dev, struct nlattr *a, *tb[IFLA_INET_MAX+1]; int err, rem;
- if (dev && !__in_dev_get_rcu(dev)) + if (dev && !__in_dev_get_rtnl(dev)) return -EAFNOSUPPORT;
err = nla_parse_nested_deprecated(tb, IFLA_INET_MAX, nla, @@ -1981,7 +1981,7 @@ static int inet_validate_link_af(const struct net_device *dev, static int inet_set_link_af(struct net_device *dev, const struct nlattr *nla, struct netlink_ext_ack *extack) { - struct in_device *in_dev = __in_dev_get_rcu(dev); + struct in_device *in_dev = __in_dev_get_rtnl(dev); struct nlattr *a, *tb[IFLA_INET_MAX+1]; int rem;