net: openvswitch: Fix the dead loop of MPLS parse

[ Upstream commit 0bdc924bfb319fb10d1113cbf091fc26fb7b1f99 ]

The unexpected MPLS packet may not end with the bottom label stack.
When there are many stacks, The label count value has wrapped around.
A dead loop occurs, soft lockup/CPU stuck finally.

stack backtrace:
UBSAN: array-index-out-of-bounds in /build/linux-0Pa0xK/linux-5.15.0/net/openvswitch/flow.c:662:26
index -1 is out of range for type '__be32 [3]'
CPU: 34 PID: 0 Comm: swapper/34 Kdump: loaded Tainted: G           OE   5.15.0-121-generic #131-Ubuntu
Hardware name: Dell Inc. PowerEdge C6420/0JP9TF, BIOS 2.12.2 07/14/2021
Call Trace:
 <IRQ>
 show_stack+0x52/0x5c
 dump_stack_lvl+0x4a/0x63
 dump_stack+0x10/0x16
 ubsan_epilogue+0x9/0x36
 __ubsan_handle_out_of_bounds.cold+0x44/0x49
 key_extract_l3l4+0x82a/0x840 [openvswitch]
 ? kfree_skbmem+0x52/0xa0
 key_extract+0x9c/0x2b0 [openvswitch]
 ovs_flow_key_extract+0x124/0x350 [openvswitch]
 ovs_vport_receive+0x61/0xd0 [openvswitch]
 ? kernel_init_free_pages.part.0+0x4a/0x70
 ? get_page_from_freelist+0x353/0x540
 netdev_port_receive+0xc4/0x180 [openvswitch]
 ? netdev_port_receive+0x180/0x180 [openvswitch]
 netdev_frame_hook+0x1f/0x40 [openvswitch]
 __netif_receive_skb_core.constprop.0+0x23a/0xf00
 __netif_receive_skb_list_core+0xfa/0x240
 netif_receive_skb_list_internal+0x18e/0x2a0
 napi_complete_done+0x7a/0x1c0
 bnxt_poll+0x155/0x1c0 [bnxt_en]
 __napi_poll+0x30/0x180
 net_rx_action+0x126/0x280
 ? bnxt_msix+0x67/0x80 [bnxt_en]
 handle_softirqs+0xda/0x2d0
 irq_exit_rcu+0x96/0xc0
 common_interrupt+0x8e/0xa0
 </IRQ>

Fixes: fbdcdd78da ("Change in Openvswitch to support MPLS label depth of 3 in ingress direction")
Signed-off-by: Faicker Mo <faicker.mo@zenlayer.com>
Acked-by: Ilya Maximets <i.maximets@ovn.org>
Reviewed-by: Aaron Conole <aconole@redhat.com>
Link: https://patch.msgid.link/259D3404-575D-4A6D-B263-1DF59A67CF89@zenlayer.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
(cherry picked from commit 8ebcd311b4866ab911d1445ead08690e67f0c488)

net/openvswitch/flow.c

@@ -788,7 +788,7 @@ static int key_extract_l3l4(struct sk_buff *skb, struct sw_flow_key *key)
 			memset(&key->ipv4, 0, sizeof(key->ipv4));
 		}
 	} else if (eth_p_mpls(key->eth.type)) {
-		u8 label_count = 1;
+		size_t label_count = 1;
 
 		memset(&key->mpls, 0, sizeof(key->mpls));
 		skb_set_inner_network_header(skb, skb->mac_len);