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net: validate veth and vxcan peer ifindexes

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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: e6f8f1a739 ("veth: Allow to create peer link with given ifindex")
Fixes: a8f820a380 ("can: add Virtual CAN Tunnel driver (vxcan)")
Reported-by: syzbot+5ba06978f34abb058571@syzkaller.appspotmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jakub Kicinski
2023-08-18 18:26:02 -07:00
committed by David S. Miller
parent c727c6f788
commit f534f6581e
4 changed files with 22 additions and 16 deletions
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4
include/net/rtnetlink.h
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@@ -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)