net/mlx5e: Fix wrong usage of fib_info_nh when routes with nexthop objects are used

Creating routes with nexthop objects while in switchdev mode leads to access to
un-allocated memory and trigger bellow call trace due to hitting WARN_ON.
This is caused due to illegal usage of fib_info_nh in TC tunnel FIB event handling to
resolve the FIB device while fib_info built in with nexthop.

Fixed by ignoring attempts to use nexthop objects with routes until support can be
properly added.

WARNING: CPU: 1 PID: 1724 at include/net/nexthop.h:468 mlx5e_tc_tun_fib_event+0x448/0x570 [mlx5_core]
CPU: 1 PID: 1724 Comm: ip Not tainted 5.15.0_for_upstream_min_debug_2021_11_09_02_04 #1
RIP: 0010:mlx5e_tc_tun_fib_event+0x448/0x570 [mlx5_core]
RSP: 0018:ffff8881349f7910 EFLAGS: 00010202
RAX: ffff8881492f1980 RBX: ffff8881349f79e8 RCX: 0000000000000000
RDX: ffff8881349f79e8 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff8881349f7950 R08: 00000000000000fe R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000000 R12: ffff88811e9d0000
R13: ffff88810eb62000 R14: ffff888106710268 R15: 0000000000000018
FS:  00007f1d5ca6e800(0000) GS:ffff88852c880000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffedba44ff8 CR3: 0000000129808004 CR4: 0000000000370ea0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 atomic_notifier_call_chain+0x42/0x60
 call_fib_notifiers+0x21/0x40
 fib_table_insert+0x479/0x6d0
 ? try_charge_memcg+0x480/0x6d0
 inet_rtm_newroute+0x65/0xb0
 rtnetlink_rcv_msg+0x2af/0x360
 ? page_add_file_rmap+0x13/0x130
 ? do_set_pte+0xcd/0x120
 ? rtnl_calcit.isra.0+0x120/0x120
 netlink_rcv_skb+0x4e/0xf0
 netlink_unicast+0x1ee/0x2b0
 netlink_sendmsg+0x22e/0x460
 sock_sendmsg+0x33/0x40
 ____sys_sendmsg+0x1d1/0x1f0
 ___sys_sendmsg+0xab/0xf0
 ? __mod_memcg_lruvec_state+0x40/0x60
 ? __mod_lruvec_page_state+0x95/0xd0
 ? page_add_new_anon_rmap+0x4e/0xf0
 ? __handle_mm_fault+0xec6/0x1470
 __sys_sendmsg+0x51/0x90
 ? internal_get_user_pages_fast+0x480/0xa10
 do_syscall_64+0x3d/0x90
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Fixes: 8914add2 ("net/mlx5e: Handle FIB events to update tunnel endpoint device")
Signed-off-by: Maor Dickman <maord@nvidia.com>
Reviewed-by: Vlad Buslov <vladbu@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_encap.c

@@ -1579,6 +1579,8 @@ mlx5e_init_fib_work_ipv4(struct mlx5e_priv *priv,
 	struct net_device *fib_dev;
 
 	fen_info = container_of(info, struct fib_entry_notifier_info, info);
+	if (fen_info->fi->nh)
+		return NULL;
 	fib_dev = fib_info_nh(fen_info->fi, 0)->fib_nh_dev;
 	if (!fib_dev || fib_dev->netdev_ops != &mlx5e_netdev_ops ||
 	    fen_info->dst_len != 32)