netdev - Re: [PATCH ipsec-next,v4 3/3] xfrm: lwtunnel: add lwtunnel support for xfrm interfaces in collect

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Date:   Tue, 11 Oct 2022 09:41:15 +0300
From:   Ido Schimmel <idosch@...sch.org>
To:     Eyal Birger <eyal.birger@...il.com>
Cc:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, steffen.klassert@...unet.com,
        herbert@...dor.apana.org.au, dsahern@...nel.org,
        contact@...elbtn.com, pablo@...filter.org,
        nicolas.dichtel@...nd.com, razor@...ckwall.org,
        daniel@...earbox.net, netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH ipsec-next,v4 3/3] xfrm: lwtunnel: add lwtunnel support
 for xfrm interfaces in collect_md mode

On Fri, Aug 26, 2022 at 02:47:00PM +0300, Eyal Birger wrote:
> diff --git a/net/core/lwtunnel.c b/net/core/lwtunnel.c
> index 9ccd64e8a666..6fac2f0ef074 100644
> --- a/net/core/lwtunnel.c
> +++ b/net/core/lwtunnel.c
> @@ -50,6 +50,7 @@ static const char *lwtunnel_encap_str(enum lwtunnel_encap_types encap_type)
>  		return "IOAM6";
>  	case LWTUNNEL_ENCAP_IP6:
>  	case LWTUNNEL_ENCAP_IP:
> +	case LWTUNNEL_ENCAP_XFRM:
>  	case LWTUNNEL_ENCAP_NONE:
>  	case __LWTUNNEL_ENCAP_MAX:
>  		/* should not have got here */

Eyal,

The warning at the bottom can be triggered [1] from user space when the
kernel is compiled with CONFIG_MODULES=y and CONFIG_XFRM=n:

 # ip route add 198.51.100.0/24 dev dummy1 encap xfrm if_id 1
 Error: lwt encapsulation type not supported.

Original report is from a private syzkaller instance which I have
reduced to the command above.

Thanks

[1]
 WARNING: CPU: 3 PID: 2746262 at net/core/lwtunnel.c:57 lwtunnel_valid_encap_type+0x4f/0x120
[...]
 Call Trace:
  <TASK>
  rtm_to_fib_config+0x211/0x350
  inet_rtm_newroute+0x3a/0xa0 
  rtnetlink_rcv_msg+0x154/0x3c0
  netlink_rcv_skb+0x49/0xf0
  netlink_unicast+0x22f/0x350 
  netlink_sendmsg+0x208/0x440 
  ____sys_sendmsg+0x21f/0x250
  ___sys_sendmsg+0x83/0xd0
  __sys_sendmsg+0x54/0xa0
  do_syscall_64+0x35/0x80
  entry_SYSCALL_64_after_hwframe+0x63/0xcd