netdev - Re: [PATCH ipsec] xfrm: fix a warning in xfrm_policy_insert

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Date:   Tue, 21 Apr 2020 11:22:37 +0200
From:   Steffen Klassert <steffen.klassert@...unet.com>
To:     Xin Long <lucien.xin@...il.com>
CC:     <netdev@...r.kernel.org>, Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Sabrina Dubroca <sd@...asysnail.net>,
        Yuehaibing <yuehaibing@...wei.com>
Subject: Re: [PATCH ipsec] xfrm: fix a warning in xfrm_policy_insert_list

Cc Yuehaibing.

On Tue, Apr 21, 2020 at 04:57:44PM +0800, Xin Long wrote:
> This waring can be triggered simply by:
> 
>   # ip xfrm policy update src 192.168.1.1/24 dst 192.168.1.2/24 dir in \
>     priority 1 mark 0 mask 0x10  #[1]
>   # ip xfrm policy update src 192.168.1.1/24 dst 192.168.1.2/24 dir in \
>     priority 2 mark 0 mask 0x1   #[2]
>   # ip xfrm policy update src 192.168.1.1/24 dst 192.168.1.2/24 dir in \
>     priority 2 mark 0 mask 0x10  #[3]
> 
> Then dmesg shows:
> 
>   [ ] WARNING: CPU: 1 PID: 7265 at net/xfrm/xfrm_policy.c:1548
>   [ ] RIP: 0010:xfrm_policy_insert_list+0x2f2/0x1030
>   [ ] Call Trace:
>   [ ]  xfrm_policy_inexact_insert+0x85/0xe50
>   [ ]  xfrm_policy_insert+0x4ba/0x680
>   [ ]  xfrm_add_policy+0x246/0x4d0
>   [ ]  xfrm_user_rcv_msg+0x331/0x5c0
>   [ ]  netlink_rcv_skb+0x121/0x350
>   [ ]  xfrm_netlink_rcv+0x66/0x80
>   [ ]  netlink_unicast+0x439/0x630
>   [ ]  netlink_sendmsg+0x714/0xbf0
>   [ ]  sock_sendmsg+0xe2/0x110
> 
> The issue was introduced by Commit 7cb8a93968e3 ("xfrm: Allow inserting
> policies with matching mark and different priorities"). After that, the
> policies [1] and [2] would be able to be added with different priorities.
> 
> However, policy [3] will actually match both [1] and [2]. Policy [1]
> was matched due to the 1st 'return true' in xfrm_policy_mark_match(),
> and policy [2] was matched due to the 2nd 'return true' in there. It
> caused WARN_ON() in xfrm_policy_insert_list().

This issue is also discussed here:

https://lkml.org/lkml/2020/4/21/77