netdev - Re: [PATCH] net: openvswitch: Fix the dead loop of MPLS parse

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Message-ID: <c7d27849-f48b-4c85-bcd9-5d2206856abd@ovn.org>
Date: Tue, 20 May 2025 15:37:53 +0200
From: Ilya Maximets <i.maximets@....org>
To: Faicker Mo <faicker.mo@...layer.com>,
 "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
 "ovs-dev@...nvswitch.org" <ovs-dev@...nvswitch.org>
Cc: i.maximets@....org, "aconole@...hat.com" <aconole@...hat.com>,
 "echaudro@...hat.com" <echaudro@...hat.com>,
 "davem@...emloft.net" <davem@...emloft.net>,
 "edumazet@...gle.com" <edumazet@...gle.com>,
 "kuba@...nel.org" <kuba@...nel.org>, "pabeni@...hat.com"
 <pabeni@...hat.com>, "horms@...nel.org" <horms@...nel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "dev@...nvswitch.org" <dev@...nvswitch.org>
Subject: Re: [PATCH] net: openvswitch: Fix the dead loop of MPLS parse

On 5/20/25 6:13 AM, Faicker Mo wrote:
> 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>
> 
> Signed-off-by: Faicker Mo <faicker.mo@...layer.com>
> ---
>  net/openvswitch/flow.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c
> index 8a848ce72e29..834b1b9110ac 100644
> --- a/net/openvswitch/flow.c
> +++ b/net/openvswitch/flow.c
> @@ -805,6 +805,8 @@ static int key_extract_l3l4(struct sk_buff *skb, struct sw_flow_key *key)
>                         if (label_count <= MPLS_LABEL_DEPTH)
>                                 memcpy(&key->mpls.lse[label_count - 1], &lse,
>                                        MPLS_HLEN);
> +                       else if (unlikely(label_count == 255))
> +                               return 0;
> 
>                         skb_set_inner_network_header(skb, skb->mac_len +
>                                                      label_count * MPLS_HLEN);
> --
> 2.34.1
> 

One other thing,

For some reason the patch was not delivered to lore.kernel.org
and is not available in netdev+bpf patchwork and not in lkml.org.
Both of our replies are available in list archives.  The original
email is available only via mail-archive, but it is ovs-dev and
not the netdev list:
  https://www.mail-archive.com/ovs-dev@openvswitch.org/msg94895.html
Same for v2.

Is kernel.org blocking the sender somehow?  Does anyone know?

Best regards, Ilya Maximets.