Re: [PATCH] xfrm: policy: Only use mark as policy lookup key

[Yuehaibing <yuehaibing@huawei.com>]

On 2020/4/22 17:33, Steffen Klassert wrote:
> On Tue, Apr 21, 2020 at 10:31:49PM +0800, YueHaibing wrote:
>> While update xfrm policy as follow:
>>
>> ip -6 xfrm policy update src fd00::1/128 dst fd00::2/128 dir in \
>>  priority 1 mark 0 mask 0x10
>> ip -6 xfrm policy update src fd00::1/128 dst fd00::2/128 dir in \
>>  priority 2 mark 0 mask 0x00
>> ip -6 xfrm policy update src fd00::1/128 dst fd00::2/128 dir in \
>>  priority 2 mark 0 mask 0x10
>>
>> We get this warning:
>>
>> WARNING: CPU: 0 PID: 4808 at net/xfrm/xfrm_policy.c:1548
>> Kernel panic - not syncing: panic_on_warn set ...
>> CPU: 0 PID: 4808 Comm: ip Not tainted 5.7.0-rc1+ #151
>> Call Trace:
>> RIP: 0010:xfrm_policy_insert_list+0x153/0x1e0
>>  xfrm_policy_inexact_insert+0x70/0x330
>>  xfrm_policy_insert+0x1df/0x250
>>  xfrm_add_policy+0xcc/0x190 [xfrm_user]
>>  xfrm_user_rcv_msg+0x1d1/0x1f0 [xfrm_user]
>>  netlink_rcv_skb+0x4c/0x120
>>  xfrm_netlink_rcv+0x32/0x40 [xfrm_user]
>>  netlink_unicast+0x1b3/0x270
>>  netlink_sendmsg+0x350/0x470
>>  sock_sendmsg+0x4f/0x60
>>
>> Policy C and policy A has the same mark.v and mark.m, so policy A is
>> matched in first round lookup while updating C. However policy C and
>> policy B has same mark and priority, which also leads to matched. So
>> the WARN_ON is triggered.
>>
>> xfrm policy lookup should only be matched when the found policy has the
>> same lookup keys (mark.v & mark.m) no matter priority.
>>
>> Fixes: 7cb8a93968e3 ("xfrm: Allow inserting policies with matching mark and different priorities")
>> Signed-off-by: YueHaibing <yuehaibing@huawei.com>
>> ---
>>  net/xfrm/xfrm_policy.c | 16 +++++-----------
>>  1 file changed, 5 insertions(+), 11 deletions(-)
>>
>> diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
>> index 297b2fd..67d0469 100644
>> --- a/net/xfrm/xfrm_policy.c
>> +++ b/net/xfrm/xfrm_policy.c
>> @@ -1436,13 +1436,7 @@ static void xfrm_policy_requeue(struct xfrm_policy *old,
>>  static bool xfrm_policy_mark_match(struct xfrm_policy *policy,
>>  				   struct xfrm_policy *pol)
>>  {
>> -	u32 mark = policy->mark.v & policy->mark.m;
>> -
>> -	if (policy->mark.v == pol->mark.v && policy->mark.m == pol->mark.m)
>> -		return true;
>> -
>> -	if ((mark & pol->mark.m) == pol->mark.v &&
>> -	    policy->priority == pol->priority)
> 
> If you remove the priority check, you can't insert policies with matching
> mark and different priorities anymore. This brings us back the old bug.

Yes, this is true.

> 
> I plan to apply the patch from Xin Long, this seems to be the right way
> to address this problem.

That still brings an issue, update like this:

policy A (mark.v = 1, mark.m = 0, priority = 1)
policy B (mark.v = 1, mark.m = 0, priority = 1)

A and B will all in the list.

So should do this:

 static bool xfrm_policy_mark_match(struct xfrm_policy *policy,
                                   struct xfrm_policy *pol)
 {
-       u32 mark = policy->mark.v & policy->mark.m;
-
-       if (policy->mark.v == pol->mark.v && policy->mark.m == pol->mark.m)
-               return true;
-
-       if ((mark & pol->mark.m) == pol->mark.v &&
+       if ((policy->mark.v & policy->mark.m) == (pol->mark.v & pol->mark.m) &&
            policy->priority == pol->priority)
                return true;



> 
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