From: Cong Wang <cong.wang@xxxxxxxxxxxxx>
[ 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@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 63ed8de4be81 ("mld: add mc_lock for protecting per-interface mld data")
Tested-by: Taehee Yoo <ap420073@xxxxxxxxx>
Signed-off-by: Cong Wang <cong.wang@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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;
--
2.30.2
