leandrof/linux
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

rtnetlink: avoid RCU read lock when holding RTNL

Browse Source 
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
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;
}
}