diff mbox series

[net,v2] rtnetlink: fix double call of rtnl_link_get_net_ifla()

Message ID 20241129212519.825567-1-xiyou.wangcong@gmail.com (mailing list archive)
State New
Delegated to: Netdev Maintainers
Headers show
Series [net,v2] rtnetlink: fix double call of rtnl_link_get_net_ifla() | expand

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Context Check Description
netdev/series_format success Single patches do not need cover letters
netdev/tree_selection success Clearly marked for net
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag present in non-next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 3 this patch: 3
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers fail 3 blamed authors not CCed: kuba@kernel.org razor@blackwall.org edumazet@google.com; 11 maintainers not CCed: kuba@kernel.org bpf@vger.kernel.org mailhol.vincent@wanadoo.fr daniel@iogearbox.net mkl@pengutronix.de andrew+netdev@lunn.ch razor@blackwall.org horms@kernel.org pabeni@redhat.com edumazet@google.com linux-can@vger.kernel.org
netdev/build_clang success Errors and warnings before: 3 this patch: 3
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 308 this patch: 308
netdev/checkpatch warning WARNING: line length of 83 exceeds 80 columns WARNING: line length of 92 exceeds 80 columns
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 5 this patch: 5
netdev/source_inline success Was 0 now: 0

Commit Message

Cong Wang Nov. 29, 2024, 9:25 p.m. UTC 
From: Cong Wang <cong.wang@bytedance.com>

Currently rtnl_link_get_net_ifla() gets called twice when we create
peer devices, once in rtnl_add_peer_net() and once in each ->newlink()
implementation.

This looks safer, however, it leads to a classic Time-of-Check to
Time-of-Use (TOCTOU) bug since IFLA_NET_NS_PID is very dynamic. And
because of the lack of checking error pointer of the second call, it
also leads to a kernel crash as reported by syzbot.

Fix this by getting rid of the second call, which already becomes
redudant after Kuniyuki's work. We have to propagate the result of the
first rtnl_link_get_net_ifla() down to each ->newlink().

Reported-by: syzbot+21ba4d5adff0b6a7cfc6@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=21ba4d5adff0b6a7cfc6
Fixes: 0eb87b02a705 ("veth: Set VETH_INFO_PEER to veth_link_ops.peer_type.")
Fixes: 6b84e558e95d ("vxcan: Set VXCAN_INFO_PEER to vxcan_link_ops.peer_type.")
Fixes: fefd5d082172 ("netkit: Set IFLA_NETKIT_PEER_INFO to netkit_link_ops.peer_type.")
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
---
 drivers/net/can/vxcan.c | 10 ++--------
 drivers/net/netkit.c    | 11 +++--------
 drivers/net/veth.c      | 12 +++--------
 net/core/rtnetlink.c    | 44 +++++++++++++++++++++--------------------
 4 files changed, 31 insertions(+), 46 deletions(-)
diff mbox series

Patch

diff --git a/drivers/net/can/vxcan.c b/drivers/net/can/vxcan.c
index da7c72105fb6..ca8811941085 100644
--- a/drivers/net/can/vxcan.c
+++ b/drivers/net/can/vxcan.c
@@ -172,13 +172,12 @@  static void vxcan_setup(struct net_device *dev)
 /* forward declaration for rtnl_create_link() */
 static struct rtnl_link_ops vxcan_link_ops;
 
-static int vxcan_newlink(struct net *net, struct net_device *dev,
+static int vxcan_newlink(struct net *peer_net, struct net_device *dev,
 			 struct nlattr *tb[], struct nlattr *data[],
 			 struct netlink_ext_ack *extack)
 {
 	struct vxcan_priv *priv;
 	struct net_device *peer;
-	struct net *peer_net;
 
 	struct nlattr *peer_tb[IFLA_MAX + 1], **tbp = tb;
 	char ifname[IFNAMSIZ];
@@ -203,20 +202,15 @@  static int vxcan_newlink(struct net *net, struct net_device *dev,
 		name_assign_type = NET_NAME_ENUM;
 	}
 
-	peer_net = rtnl_link_get_net(net, tbp);
 	peer = rtnl_create_link(peer_net, ifname, name_assign_type,
 				&vxcan_link_ops, tbp, extack);
-	if (IS_ERR(peer)) {
-		put_net(peer_net);
+	if (IS_ERR(peer))
 		return PTR_ERR(peer);
-	}
 
 	if (ifmp && dev->ifindex)
 		peer->ifindex = ifmp->ifi_index;
 
 	err = register_netdevice(peer);
-	put_net(peer_net);
-	peer_net = NULL;
 	if (err < 0) {
 		free_netdev(peer);
 		return err;
diff --git a/drivers/net/netkit.c b/drivers/net/netkit.c
index bb07725d1c72..c1d881dc6409 100644
--- a/drivers/net/netkit.c
+++ b/drivers/net/netkit.c
@@ -327,7 +327,7 @@  static int netkit_validate(struct nlattr *tb[], struct nlattr *data[],
 
 static struct rtnl_link_ops netkit_link_ops;
 
-static int netkit_new_link(struct net *src_net, struct net_device *dev,
+static int netkit_new_link(struct net *peer_net, struct net_device *dev,
 			   struct nlattr *tb[], struct nlattr *data[],
 			   struct netlink_ext_ack *extack)
 {
@@ -342,7 +342,6 @@  static int netkit_new_link(struct net *src_net, struct net_device *dev,
 	struct net_device *peer;
 	char ifname[IFNAMSIZ];
 	struct netkit *nk;
-	struct net *net;
 	int err;
 
 	if (data) {
@@ -385,13 +384,10 @@  static int netkit_new_link(struct net *src_net, struct net_device *dev,
 	    (tb[IFLA_ADDRESS] || tbp[IFLA_ADDRESS]))
 		return -EOPNOTSUPP;
 
-	net = rtnl_link_get_net(src_net, tbp);
-	peer = rtnl_create_link(net, ifname, ifname_assign_type,
+	peer = rtnl_create_link(peer_net, ifname, ifname_assign_type,
 				&netkit_link_ops, tbp, extack);
-	if (IS_ERR(peer)) {
-		put_net(net);
+	if (IS_ERR(peer))
 		return PTR_ERR(peer);
-	}
 
 	netif_inherit_tso_max(peer, dev);
 
@@ -408,7 +404,6 @@  static int netkit_new_link(struct net *src_net, struct net_device *dev,
 	bpf_mprog_bundle_init(&nk->bundle);
 
 	err = register_netdevice(peer);
-	put_net(net);
 	if (err < 0)
 		goto err_register_peer;
 	netif_carrier_off(peer);
diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index 0d6d0d749d44..07ebb800edf1 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -1765,7 +1765,7 @@  static int veth_init_queues(struct net_device *dev, struct nlattr *tb[])
 	return 0;
 }
 
-static int veth_newlink(struct net *src_net, struct net_device *dev,
+static int veth_newlink(struct net *peer_net, struct net_device *dev,
 			struct nlattr *tb[], struct nlattr *data[],
 			struct netlink_ext_ack *extack)
 {
@@ -1776,7 +1776,6 @@  static int veth_newlink(struct net *src_net, struct net_device *dev,
 	struct nlattr *peer_tb[IFLA_MAX + 1], **tbp;
 	unsigned char name_assign_type;
 	struct ifinfomsg *ifmp;
-	struct net *net;
 
 	/*
 	 * create and register peer first
@@ -1800,13 +1799,10 @@  static int veth_newlink(struct net *src_net, struct net_device *dev,
 		name_assign_type = NET_NAME_ENUM;
 	}
 
-	net = rtnl_link_get_net(src_net, tbp);
-	peer = rtnl_create_link(net, ifname, name_assign_type,
+	peer = rtnl_create_link(peer_net, ifname, name_assign_type,
 				&veth_link_ops, tbp, extack);
-	if (IS_ERR(peer)) {
-		put_net(net);
+	if (IS_ERR(peer))
 		return PTR_ERR(peer);
-	}
 
 	if (!ifmp || !tbp[IFLA_ADDRESS])
 		eth_hw_addr_random(peer);
@@ -1817,8 +1813,6 @@  static int veth_newlink(struct net *src_net, struct net_device *dev,
 	netif_inherit_tso_max(peer, dev);
 
 	err = register_netdevice(peer);
-	put_net(net);
-	net = NULL;
 	if (err < 0)
 		goto err_register_peer;
 
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 58df76fe408a..ab5f201bf0ab 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -3746,6 +3746,7 @@  static int rtnl_group_changelink(const struct sk_buff *skb,
 static int rtnl_newlink_create(struct sk_buff *skb, struct ifinfomsg *ifm,
 			       const struct rtnl_link_ops *ops,
 			       struct net *tgt_net, struct net *link_net,
+			       struct net *peer_net,
 			       const struct nlmsghdr *nlh,
 			       struct nlattr **tb, struct nlattr **data,
 			       struct netlink_ext_ack *extack)
@@ -3776,8 +3777,13 @@  static int rtnl_newlink_create(struct sk_buff *skb, struct ifinfomsg *ifm,
 
 	dev->ifindex = ifm->ifi_index;
 
+	if (link_net)
+		net = link_net;
+	if (peer_net)
+		net = peer_net;
+
 	if (ops->newlink)
-		err = ops->newlink(link_net ? : net, dev, tb, data, extack);
+		err = ops->newlink(net, dev, tb, data, extack);
 	else
 		err = register_netdevice(dev);
 	if (err < 0) {
@@ -3812,40 +3818,33 @@  static int rtnl_newlink_create(struct sk_buff *skb, struct ifinfomsg *ifm,
 	goto out;
 }
 
-static int rtnl_add_peer_net(struct rtnl_nets *rtnl_nets,
-			     const struct rtnl_link_ops *ops,
-			     struct nlattr *data[],
-			     struct netlink_ext_ack *extack)
+static struct net *rtnl_get_peer_net(const struct rtnl_link_ops *ops,
+				     struct nlattr *data[],
+				     struct netlink_ext_ack *extack)
 {
 	struct nlattr *tb[IFLA_MAX + 1];
-	struct net *net;
 	int err;
 
 	if (!data || !data[ops->peer_type])
-		return 0;
+		return NULL;
 
 	err = rtnl_nla_parse_ifinfomsg(tb, data[ops->peer_type], extack);
 	if (err < 0)
-		return err;
+		return ERR_PTR(err);
 
 	if (ops->validate) {
 		err = ops->validate(tb, NULL, extack);
 		if (err < 0)
-			return err;
+			return ERR_PTR(err);
 	}
 
-	net = rtnl_link_get_net_ifla(tb);
-	if (IS_ERR(net))
-		return PTR_ERR(net);
-	if (net)
-		rtnl_nets_add(rtnl_nets, net);
-
-	return 0;
+	return rtnl_link_get_net_ifla(tb);
 }
 
 static int __rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 			  const struct rtnl_link_ops *ops,
 			  struct net *tgt_net, struct net *link_net,
+			  struct net *peer_net,
 			  struct rtnl_newlink_tbs *tbs,
 			  struct nlattr **data,
 			  struct netlink_ext_ack *extack)
@@ -3894,14 +3893,15 @@  static int __rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 		return -EOPNOTSUPP;
 	}
 
-	return rtnl_newlink_create(skb, ifm, ops, tgt_net, link_net, nlh, tb, data, extack);
+	return rtnl_newlink_create(skb, ifm, ops, tgt_net, link_net, peer_net, nlh,
+				   tb, data, extack);
 }
 
 static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 			struct netlink_ext_ack *extack)
 {
+	struct net *tgt_net, *link_net = NULL, *peer_net = NULL;
 	struct nlattr **tb, **linkinfo, **data = NULL;
-	struct net *tgt_net, *link_net = NULL;
 	struct rtnl_link_ops *ops = NULL;
 	struct rtnl_newlink_tbs *tbs;
 	struct rtnl_nets rtnl_nets;
@@ -3971,9 +3971,11 @@  static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 		}
 
 		if (ops->peer_type) {
-			ret = rtnl_add_peer_net(&rtnl_nets, ops, data, extack);
-			if (ret < 0)
+			peer_net = rtnl_get_peer_net(ops, data, extack);
+			if (IS_ERR(peer_net))
 				goto put_ops;
+			if (peer_net)
+				rtnl_nets_add(&rtnl_nets, peer_net);
 		}
 	}
 
@@ -4004,7 +4006,7 @@  static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 	}
 
 	rtnl_nets_lock(&rtnl_nets);
-	ret = __rtnl_newlink(skb, nlh, ops, tgt_net, link_net, tbs, data, extack);
+	ret = __rtnl_newlink(skb, nlh, ops, tgt_net, link_net, peer_net, tbs, data, extack);
 	rtnl_nets_unlock(&rtnl_nets);
 
 put_net: