diff options
| author | Cong Wang | 2021-05-08 11:00:33 -0700 |
|---|---|---|
| committer | David S. Miller | 2021-05-10 14:33:10 -0700 |
| commit | a100243d95a60d74ae9bb9df1f5f2192e9aed6a7 (patch) | |
| tree | 5c614edec5ccc729eae58fb83e8ef43026f9e9ad /net/core | |
| parent | 3f8fca5d43357ab3ae678d908ac3c74e07503f0d (diff) | |
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: 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>
Diffstat (limited to 'net/core')
| -rw-r--r-- | net/core/rtnetlink.c | 26 |
1 files changed, 7 insertions, 19 deletions
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index 714d5fa38546..04b4f0f2a3d2 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; } } |