OpenCloudOS-Kernel/net/core
Mauricio Faria de Oliveira bd961c9bc6 rtnetlink: fix rtnl_fdb_dump() for ndmsg header
Currently, rtnl_fdb_dump() assumes the family header is 'struct ifinfomsg',
which is not always true -- 'struct ndmsg' is used by iproute2 ('ip neigh').

The problem is, the function bails out early if nlmsg_parse() fails, which
does occur for iproute2 usage of 'struct ndmsg' because the payload length
is shorter than the family header alone (as 'struct ifinfomsg' is assumed).

This breaks backward compatibility with userspace -- nothing is sent back.

Some examples with iproute2 and netlink library for go [1]:

 1) $ bridge fdb show
    33:33:00:00:00:01 dev ens3 self permanent
    01:00:5e:00:00:01 dev ens3 self permanent
    33:33:ff:15:98:30 dev ens3 self permanent

      This one works, as it uses 'struct ifinfomsg'.

      fdb_show() @ iproute2/bridge/fdb.c
        """
        .n.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg)),
        ...
        if (rtnl_dump_request(&rth, RTM_GETNEIGH, [...]
        """

 2) $ ip --family bridge neigh
    RTNETLINK answers: Invalid argument
    Dump terminated

      This one fails, as it uses 'struct ndmsg'.

      do_show_or_flush() @ iproute2/ip/ipneigh.c
        """
        .n.nlmsg_type = RTM_GETNEIGH,
        .n.nlmsg_len = NLMSG_LENGTH(sizeof(struct ndmsg)),
        """

 3) $ ./neighlist
    < no output >

      This one fails, as it uses 'struct ndmsg'-based.

      neighList() @ netlink/neigh_linux.go
        """
        req := h.newNetlinkRequest(unix.RTM_GETNEIGH, [...]
        msg := Ndmsg{
        """

The actual breakage was introduced by commit 0ff50e83b5 ("net: rtnetlink:
bail out from rtnl_fdb_dump() on parse error"), because nlmsg_parse() fails
if the payload length (with the _actual_ family header) is less than the
family header length alone (which is assumed, in parameter 'hdrlen').
This is true in the examples above with struct ndmsg, with size and payload
length shorter than struct ifinfomsg.

However, that commit just intends to fix something under the assumption the
family header is indeed an 'struct ifinfomsg' - by preventing access to the
payload as such (via 'ifm' pointer) if the payload length is not sufficient
to actually contain it.

The assumption was introduced by commit 5e6d243587 ("bridge: netlink dump
interface at par with brctl"), to support iproute2's 'bridge fdb' command
(not 'ip neigh') which indeed uses 'struct ifinfomsg', thus is not broken.

So, in order to unbreak the 'struct ndmsg' family headers and still allow
'struct ifinfomsg' to continue to work, check for the known message sizes
used with 'struct ndmsg' in iproute2 (with zero or one attribute which is
not used in this function anyway) then do not parse the data as ifinfomsg.

Same examples with this patch applied (or revert/before the original fix):

    $ bridge fdb show
    33:33:00:00:00:01 dev ens3 self permanent
    01:00:5e:00:00:01 dev ens3 self permanent
    33:33:ff:15:98:30 dev ens3 self permanent

    $ ip --family bridge neigh
    dev ens3 lladdr 33:33:00:00:00:01 PERMANENT
    dev ens3 lladdr 01:00:5e:00:00:01 PERMANENT
    dev ens3 lladdr 33:33:ff:15:98:30 PERMANENT

    $ ./neighlist
    netlink.Neigh{LinkIndex:2, Family:7, State:128, Type:0, Flags:2, IP:net.IP(nil), HardwareAddr:net.HardwareAddr{0x33, 0x33, 0x0, 0x0, 0x0, 0x1}, LLIPAddr:net.IP(nil), Vlan:0, VNI:0}
    netlink.Neigh{LinkIndex:2, Family:7, State:128, Type:0, Flags:2, IP:net.IP(nil), HardwareAddr:net.HardwareAddr{0x1, 0x0, 0x5e, 0x0, 0x0, 0x1}, LLIPAddr:net.IP(nil), Vlan:0, VNI:0}
    netlink.Neigh{LinkIndex:2, Family:7, State:128, Type:0, Flags:2, IP:net.IP(nil), HardwareAddr:net.HardwareAddr{0x33, 0x33, 0xff, 0x15, 0x98, 0x30}, LLIPAddr:net.IP(nil), Vlan:0, VNI:0}

Tested on mainline (v4.19-rc6) and net-next (3bd09b05b0).

References:

[1] netlink library for go (test-case)
    https://github.com/vishvananda/netlink

    $ cat ~/go/src/neighlist/main.go
    package main
    import ("fmt"; "syscall"; "github.com/vishvananda/netlink")
    func main() {
        neighs, _ := netlink.NeighList(0, syscall.AF_BRIDGE)
        for _, neigh := range neighs { fmt.Printf("%#v\n", neigh) }
    }

    $ export GOPATH=~/go
    $ go get github.com/vishvananda/netlink
    $ go build neighlist
    $ ~/go/src/neighlist/neighlist

Thanks to David Ahern for suggestions to improve this patch.

Fixes: 0ff50e83b5 ("net: rtnetlink: bail out from rtnl_fdb_dump() on parse error")
Fixes: 5e6d243587 ("bridge: netlink dump interface at par with brctl")
Reported-by: Aidan Obley <aobley@pivotal.io>
Signed-off-by: Mauricio Faria de Oliveira <mfo@canonical.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-10-05 14:21:42 -07:00
..
Makefile net: Introduce generic failover module 2018-05-28 22:59:54 -04:00
datagram.c net: simplify sock_poll_wait 2018-07-30 09:10:25 -07:00
dev.c notifier: Remove notifier header file wherever not used 2018-08-30 12:56:40 +02:00
dev_addr_lists.c net: change the comment of dev_mc_init 2018-04-19 12:58:20 -04:00
dev_ioctl.c net: remove redundant input checks in SIOCSIFTXQLEN case of dev_ifsioc 2018-07-24 11:36:15 -07:00
devlink.c devlink: double free in devlink_resource_fill() 2018-09-21 19:19:07 -07:00
drop_monitor.c treewide: setup_timer() -> timer_setup() 2017-11-21 15:57:07 -08:00
dst.c netfilter: nf_tables: add tunnel support 2018-08-03 21:12:12 +02:00
dst_cache.c net: core: dst_cache_set_ip6: Rename 'addr' parameter to 'saddr' for consistency 2018-03-05 12:52:45 -05:00
ethtool.c net: core: add member wol_enabled to struct net_device 2018-09-26 20:04:11 -07:00
failover.c net: Introduce generic failover module 2018-05-28 22:59:54 -04:00
fib_notifier.c net: Fix fib notifer to return errno 2018-03-29 14:10:30 -04:00
fib_rules.c fib_rules: NULL check before kfree is not needed 2018-07-30 09:44:06 -07:00
filter.c bpf: use __GFP_COMP while allocating page 2018-09-12 23:47:28 +02:00
flow_dissector.c flow_dissector: allow dissection of tunnel options from metadata 2018-08-07 12:22:14 -07:00
gen_estimator.c net: core: protect rate estimator statistics pointer with lock 2018-08-11 12:37:10 -07:00
gen_stats.c gen_stats: Fix netlink stats dumping in the presence of padding 2018-07-04 14:44:45 +09:00
gro_cells.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
hwbm.c net: hwbm: Fix unbalanced spinlock in error case 2016-05-25 12:35:09 -07:00
link_watch.c net: link_watch: mark bonding link events urgent 2018-01-23 19:43:30 -05:00
lwt_bpf.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2018-08-07 11:02:05 -07:00
lwtunnel.c ipv6: sr: define core operations for seg6local lightweight tunnel 2017-08-07 14:16:22 -07:00
neighbour.c neighbour: confirm neigh entries when ARP packet is received 2018-09-13 12:01:29 -07:00
net-procfs.c proc: introduce proc_create_net{,_data} 2018-05-16 07:24:30 +02:00
net-sysfs.c net: allow to call netif_reset_xps_queues() under cpus_read_lock 2018-08-09 14:25:06 -07:00
net-sysfs.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
net-traces.c net/ipv6: Udate fib6_table_lookup tracepoint 2018-05-24 23:01:15 -04:00
net_namespace.c Merge branch 'ida-4.19' of git://git.infradead.org/users/willy/linux-dax 2018-08-26 11:48:42 -07:00
netclassid_cgroup.c cgroup: add @flags to css_task_iter_start() and implement CSS_TASK_ITER_PROCS 2017-07-21 11:14:51 -04:00
netevent.c netevent: remove automatic variable in register_netevent_notifier() 2015-05-31 00:03:21 -07:00
netpoll.c bond: take rcu lock in netpoll_send_skb_on_dev 2018-10-01 23:25:25 -07:00
netprio_cgroup.c net: remove duplicate includes 2017-12-13 13:18:46 -05:00
page_pool.c net/page_pool: Fix inconsistent lock state warning 2018-07-19 23:23:01 -07:00
pktgen.c Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec-next 2018-07-27 09:33:37 -07:00
ptp_classifier.c ptp: Change ptp_class to a proper bitmask 2015-11-03 11:08:22 -05:00
request_sock.c ipv4: Namespaceify tcp_max_syn_backlog knob 2016-12-29 11:38:31 -05:00
rtnetlink.c rtnetlink: fix rtnl_fdb_dump() for ndmsg header 2018-10-05 14:21:42 -07:00
scm.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/user.h> 2017-03-02 08:42:29 +01:00
secure_seq.c infiniband: i40iw, nes: don't use wall time for TCP sequence numbers 2018-07-11 12:10:19 -06:00
skbuff.c tcp: really ignore MSG_ZEROCOPY if no SO_ZEROCOPY 2018-09-07 23:11:06 -07:00
sock.c net: avoid unnecessary sock_flag() check when enable timestamp 2018-08-06 10:42:48 -07:00
sock_diag.c net: sock_diag: Fix spectre v1 gadget in __sock_diag_cmd() 2018-08-14 10:01:24 -07:00
sock_reuseport.c bpf: Enable BPF_PROG_TYPE_SK_REUSEPORT bpf prog in reuseport selection 2018-08-11 01:58:46 +02:00
stream.c vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
sysctl_net_core.c headers: untangle kmemleak.h from mm.h 2018-04-05 21:36:27 -07:00
timestamping.c net: skb_defer_rx_timestamp should check for phydev before setting up classify 2015-07-09 14:17:15 -07:00
tso.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
utils.c net: Remove some unneeded semicolon 2018-08-04 13:05:39 -07:00
xdp.c net/xdp: Fix suspicious RCU usage warning 2018-08-16 21:55:21 +02:00