[PATCH net mlxsw v2] mlxsw: spectrum: Forbid creation of VLAN 1 over port/LAG

[Petr Machata]

VLAN 1 is internally used for untagged traffic. Prevent creation of
explicit netdevice for that VLAN, because that currently isn't supported
and leads to the NULL pointer dereference cited below.

Fix by preventing creation of VLAN devices with VID of 1 over mlxsw
devices or LAG devices that involve mlxsw devices.

[  327.175816] ================================================================================
[  327.184544] UBSAN: Undefined behaviour in drivers/net/ethernet/mellanox/mlxsw/spectrum_fid.c:200:12
[  327.193667] member access within null pointer of type 'const struct mlxsw_sp_fid'
[  327.201226] CPU: 0 PID: 8983 Comm: ip Not tainted 4.17.0-rc4-petrm_net_ip6gre_headroom-custom-140 #11
[  327.210496] Hardware name: Mellanox Technologies Ltd. "MSN2410-CB2F"/"SA000874", BIOS 4.6.5 03/08/2016
[  327.219872] Call Trace:
[  327.222384]  dump_stack+0xc3/0x12b
[  327.234007]  ubsan_epilogue+0x9/0x49
[  327.237638]  ubsan_type_mismatch_common+0x1f9/0x2d0
[  327.255769]  __ubsan_handle_type_mismatch+0x90/0xa7
[  327.264716]  mlxsw_sp_fid_type+0x35/0x50 [mlxsw_spectrum]
[  327.270255]  mlxsw_sp_port_vlan_router_leave+0x46/0xc0 [mlxsw_spectrum]
[  327.277019]  mlxsw_sp_inetaddr_port_vlan_event+0xe1/0x340 [mlxsw_spectrum]
[  327.315031]  mlxsw_sp_netdevice_vrf_event+0xa8/0x100 [mlxsw_spectrum]
[  327.321626]  mlxsw_sp_netdevice_event+0x276/0x430 [mlxsw_spectrum]
[  327.367863]  notifier_call_chain+0x4c/0x150
[  327.372128]  __netdev_upper_dev_link+0x1b3/0x260
[  327.399450]  vrf_add_slave+0xce/0x170 [vrf]
[  327.403703]  do_setlink+0x658/0x1d70
[  327.508998]  rtnl_newlink+0x908/0xf20
[  327.559128]  rtnetlink_rcv_msg+0x50c/0x720
[  327.571720]  netlink_rcv_skb+0x16a/0x1f0
[  327.583450]  netlink_unicast+0x2ca/0x3e0
[  327.599305]  netlink_sendmsg+0x3e2/0x7f0
[  327.616655]  sock_sendmsg+0x76/0xc0
[  327.620207]  ___sys_sendmsg+0x494/0x5d0
[  327.666117]  __sys_sendmsg+0xc2/0x130
[  327.690953]  do_syscall_64+0x66/0x370
[  327.694677]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  327.699782] RIP: 0033:0x7f4c2f3f8037
[  327.703393] RSP: 002b:00007ffe8c389708 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
[  327.711035] RAX: ffffffffffffffda RBX: 000000005b03f53e RCX: 00007f4c2f3f8037
[  327.718229] RDX: 0000000000000000 RSI: 00007ffe8c389760 RDI: 0000000000000003
[  327.725431] RBP: 00007ffe8c389760 R08: 0000000000000000 R09: 00007f4c2f443630
[  327.732632] R10: 00000000000005eb R11: 0000000000000246 R12: 0000000000000000
[  327.739833] R13: 00000000006774e0 R14: 00007ffe8c3897e8 R15: 0000000000000000
[  327.747096] ================================================================================

Fixes: 9589a7b5d7d9 ("mlxsw: spectrum: Handle VLAN devices linking / unlinking")
Suggested-by: Ido Schimmel <idosch at mellanox.com>
Signed-off-by: Petr Machata <petrm at mellanox.com>
---

Notes:
    Changes from v1 to v2:
    
    - Change the rejection error code from -EINVAL to -EOPNOTSUPP.

 drivers/net/ethernet/mellanox/mlxsw/spectrum.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum.c
index ca38a30..dbb729a 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum.c
@@ -4433,6 +4433,11 @@ static int mlxsw_sp_netdevice_port_upper_event(struct net_device *lower_dev,
 			NL_SET_ERR_MSG_MOD(extack, "Can not put a VLAN on an OVS port");
 			return -EINVAL;
 		}
+		if (is_vlan_dev(upper_dev) &&
+		    vlan_dev_vlan_id(upper_dev) == 1) {
+			NL_SET_ERR_MSG_MOD(extack, "Creating a VLAN device with VID 1 is unsupported: VLAN 1 carries untagged traffic");
+			return -EOPNOTSUPP;
+		}
 		break;
 	case NETDEV_CHANGEUPPER:
 		upper_dev = info->upper_dev;
-- 
2.4.11