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rtnetlink: avoid RCU read lock when holding RTNL 

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: 63ed8de4be ("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>
This commit is contained in:
Cong Wang 2021-05-08 11:00:33 -07:00 committed by David S. Miller
parent 3f8fca5d43
commit a100243d95
2 changed files with 9 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
net/core/rtnetlink.c
View File

@ -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;
}
}

4
net/ipv4/devinet.c
View File

@ -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;