[PATCH net-next v3] net: openvswitch: Fix the dead loop of MPLS parse

[PATCH net-next v3] net: openvswitch: Fix the dead loop of MPLS parse

[Faicker Mo]

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: fbdcdd78da7c ("Change in Openvswitch to support MPLS label depth of 3 in ingress direction")
Signed-off-by: Faicker Mo <faicker.mo@zenlayer.com>
---
v2
- Changed return value based on Eelco's feedback.
- Added Fixes.
v3
- Revert "Changed return value based on Eelco's feedback".
- Changed the label_count variable type based on Ilya's feedback.
---
net/openvswitch/flow.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c
index 8a848ce72e29..b80bd3a90773 100644
--- a/net/openvswitch/flow.c
+++ b/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);
--
2.34.1

Re: [PATCH net-next v3] net: openvswitch: Fix the dead loop of MPLS parse

[Aaron Conole]

Hi Faicker,

Faicker Mo <faicker.mo@zenlayer.com> writes:

> 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: fbdcdd78da7c ("Change in Openvswitch to support MPLS label depth of 3 in ingress direction")

This tells me it should go to 'net' rather than 'net-next', so your
subject should look like:

  [PATCH net v4] net: openvswitch: Fix the dead loop of MPLS parse

> Signed-off-by: Faicker Mo <faicker.mo@zenlayer.com>
> ---
> v2
> - Changed return value based on Eelco's feedback.
> - Added Fixes.
> v3
> - Revert "Changed return value based on Eelco's feedback".
> - Changed the label_count variable type based on Ilya's feedback.


Somehow, this patch is still getting corrupted.  For example, it is
missing the leading ' ' character in the diffs.  This is one reason
the patch fails to apply.

> ---
> net/openvswitch/flow.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c
> index 8a848ce72e29..b80bd3a90773 100644
> --- a/net/openvswitch/flow.c
> +++ b/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;

This change looks good to me.

>
> 		memset(&key->mpls, 0, sizeof(key->mpls));
> 		skb_set_inner_network_header(skb, skb->mac_len);
> --
> 2.34.1