veth and vxcan need to make sure the ifindexes of the peer
are not negative, core does not validate this.
Using iproute2 with user-space-level checking removed:
Before:
# ./ip link add index 10 type veth peer index -1
# ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
link/ether 52:54:00:74:b2:03 brd ff:ff:ff:ff:ff:ff
10: veth1@veth0: <BROADCAST,MULTICAST,M-DOWN> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
link/ether 8a:90:ff:57:6d:5d brd ff:ff:ff:ff:ff:ff
-1: veth0@veth1: <BROADCAST,MULTICAST,M-DOWN> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
link/ether ae:ed:18:e6:fa:7f brd ff:ff:ff:ff:ff:ff
Now:
$ ./ip link add index 10 type veth peer index -1
Error: ifindex can't be negative.
This problem surfaced in net-next because an explicit WARN()
was added, the root cause is older.
Fixes: e6f8f1a739b6 ("veth: Allow to create peer link with given ifindex")
Fixes: a8f820a380a2 ("can: add Virtual CAN Tunnel driver (vxcan)")
Reported-by: syzbot+5ba06978f34abb058571@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
---
CC: wg@xxxxxxxxxxxxxx
CC: mkl@xxxxxxxxxxxxxx
CC: idosch@xxxxxxxxxx
CC: lucien.xin@xxxxxxxxx
CC: xemul@xxxxxxxxxxxxx
CC: socketcan@xxxxxxxxxxxx
CC: linux-can@xxxxxxxxxxxxxxx
---
drivers/net/can/vxcan.c | 7 +------
drivers/net/veth.c | 5 +----
include/net/rtnetlink.h | 4 ++--
net/core/rtnetlink.c | 22 ++++++++++++++++++----
4 files changed, 22 insertions(+), 16 deletions(-)
diff --git a/drivers/net/can/vxcan.c b/drivers/net/can/vxcan.c
index 4068d962203d..98c669ad5141 100644
--- a/drivers/net/can/vxcan.c
+++ b/drivers/net/can/vxcan.c
@@ -192,12 +192,7 @@ static int vxcan_newlink(struct net *net, struct net_device *dev,
nla_peer = data[VXCAN_INFO_PEER];
ifmp = nla_data(nla_peer);
- err = rtnl_nla_parse_ifla(peer_tb,
- nla_data(nla_peer) +
- sizeof(struct ifinfomsg),
- nla_len(nla_peer) -
- sizeof(struct ifinfomsg),
- NULL);
+ err = rtnl_nla_parse_ifinfomsg(peer_tb, nla_peer, extack);
if (err < 0)
return err;
diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index 509e901da41d..ef8eacb596f7 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -1861,10 +1861,7 @@ static int veth_newlink(struct net *src_net, struct net_device *dev,
nla_peer = data[VETH_INFO_PEER];
ifmp = nla_data(nla_peer);
- err = rtnl_nla_parse_ifla(peer_tb,
- nla_data(nla_peer) + sizeof(struct ifinfomsg),
- nla_len(nla_peer) - sizeof(struct ifinfomsg),
- NULL);
+ err = rtnl_nla_parse_ifinfomsg(peer_tb, nla_peer, extack);
if (err < 0)
return err;
diff --git a/include/net/rtnetlink.h b/include/net/rtnetlink.h
index d9076a7a430c..6506221c5fe3 100644
--- a/include/net/rtnetlink.h
+++ b/include/net/rtnetlink.h
@@ -190,8 +190,8 @@ int rtnl_delete_link(struct net_device *dev, u32 portid, const struct nlmsghdr *
int rtnl_configure_link(struct net_device *dev, const struct ifinfomsg *ifm,
u32 portid, const struct nlmsghdr *nlh);
-int rtnl_nla_parse_ifla(struct nlattr **tb, const struct nlattr *head, int len,
- struct netlink_ext_ack *exterr);
+int rtnl_nla_parse_ifinfomsg(struct nlattr **tb, const struct nlattr *nla_peer,
+ struct netlink_ext_ack *exterr);
struct net *rtnl_get_net_ns_capable(struct sock *sk, int netnsid);
#define MODULE_ALIAS_RTNL_LINK(kind) MODULE_ALIAS("rtnl-link-" kind)
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index aef25aa5cf1d..bcebdeb59163 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -2268,13 +2268,27 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
return err;
}
-int rtnl_nla_parse_ifla(struct nlattr **tb, const struct nlattr *head, int len,
- struct netlink_ext_ack *exterr)
+int rtnl_nla_parse_ifinfomsg(struct nlattr **tb, const struct nlattr *nla_peer,
+ struct netlink_ext_ack *exterr)
{
- return nla_parse_deprecated(tb, IFLA_MAX, head, len, ifla_policy,
+ const struct ifinfomsg *ifmp;
+ const struct nlattr *attrs;
+ size_t len;
+
+ ifmp = nla_data(nla_peer);
+ attrs = nla_data(nla_peer) + sizeof(struct ifinfomsg);
+ len = nla_len(nla_peer) - sizeof(struct ifinfomsg);
+
+ if (ifmp->ifi_index < 0) {
+ NL_SET_ERR_MSG_ATTR(exterr, nla_peer,
+ "ifindex can't be negative");
+ return -EINVAL;
+ }
+
+ return nla_parse_deprecated(tb, IFLA_MAX, attrs, len, ifla_policy,
exterr);
}
-EXPORT_SYMBOL(rtnl_nla_parse_ifla);
+EXPORT_SYMBOL(rtnl_nla_parse_ifinfomsg);
struct net *rtnl_link_get_net(struct net *src_net, struct nlattr *tb[])
{
--
2.41.0
