vrf: revert "vrf: Remove unnecessary RCU-bh critical section"

In the Linux kernel, the following vulnerability has been resolved:

vrf: revert "vrf: Remove unnecessary RCU-bh critical section"

This reverts commit 504fc6f4f7f681d2a03aa5f68aad549d90eab853.

dev_queue_xmit_nit is expected to be called with BH disabled.

__dev_queue_xmit has the following:

/* Disable soft irqs for various locks below. Also

* stops preemption for RCU.

*/

rcu_read_lock_bh();

VRF must follow this invariant. The referenced commit removed this

protection. Which triggered a lockdep warning:

================================

WARNING: inconsistent lock state

6.11.0 #1 Tainted: G W

--------------------------------

inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage.

btserver/134819 [HC0[0]:SC0[0]:HE1:SE1] takes:

ffff8882da30c118 (rlock-AF_PACKET){+.?.}-{2:2}, at: tpacket_rcv+0x863/0x3b30

{IN-SOFTIRQ-W} state was registered at:

lock_acquire+0x19a/0x4f0

_raw_spin_lock+0x27/0x40

packet_rcv+0xa33/0x1320

__netif_receive_skb_core.constprop.0+0xcb0/0x3a90

__netif_receive_skb_list_core+0x2c9/0x890

netif_receive_skb_list_internal+0x610/0xcc0

[...]

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0

----

lock(rlock-AF_PACKET);

<Interrupt>

lock(rlock-AF_PACKET);

*** DEADLOCK ***

Call Trace:

<TASK>

dump_stack_lvl+0x73/0xa0

mark_lock+0x102e/0x16b0

__lock_acquire+0x9ae/0x6170

lock_acquire+0x19a/0x4f0

_raw_spin_lock+0x27/0x40

tpacket_rcv+0x863/0x3b30

dev_queue_xmit_nit+0x709/0xa40

vrf_finish_direct+0x26e/0x340 [vrf]

vrf_l3_out+0x5f4/0xe80 [vrf]

__ip_local_out+0x51e/0x7a0

[...]