Messages in this thread | | | From | Xin Long <> | Date | Thu, 23 Apr 2020 17:43:11 +0800 | Subject | Re: [PATCH] xfrm: policy: Only use mark as policy lookup key |
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On Thu, Apr 23, 2020 at 4:41 PM Yuehaibing <yuehaibing@huawei.com> wrote: > > On 2020/4/23 14:37, Xin Long wrote: > > On Thu, Apr 23, 2020 at 10:26 AM Yuehaibing <yuehaibing@huawei.com> wrote: > >> > >> On 2020/4/22 23:41, Xin Long wrote: > >>> On Wed, Apr 22, 2020 at 8:18 PM Yuehaibing <yuehaibing@huawei.com> wrote: > >>>> > >>>> 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. > >>> I think this is another issue even before: > >>> 7cb8a93968e3 ("xfrm: Allow inserting policies with matching mark and > >>> different priorities") > >>> > >>>> > >>>> 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; > >>> "mark.v & mark.m" looks weird to me, it should be: > >>> ((something & mark.m) == mark.v) > >>> > >>> So why should we just do this here?: > >>> (policy->mark.v == pol->mark.v && policy->mark.m == pol->mark.m && > >>> policy->priority == pol->priority) > >> > >> > >> This leads to this issue: > >> > >> ip -6 xfrm policy add src fd00::1/128 dst fd00::2/128 dir in mark 0x00000001 mask 0x00000005 > >> ip -6 xfrm policy add src fd00::1/128 dst fd00::2/128 dir in mark 0x00000001 mask 0x00000003 > >> > >> the two policies will be in list, which should not be allowed. > > I think these are two different policies. > > For instance: > > mark = 0x1234567b will match the 1st one only. > > mark = 0x1234567d will match the 2st one only > > > > So these should have been allowed, no? > > If mark = 0x12345671, it may match different policy depends on the order of inserting, > > ip xfrm policy update src 172.16.2.0/24 dst 172.16.1.0/24 dir in ptype main \ > tmpl src 192.168.2.10 dst 192.168.1.20 proto esp mode tunnel mark 0x00000001 mask 0x00000005 > > ip xfrm policy update src 172.16.2.0/24 dst 172.16.1.0/24 dir in ptype main \ > tmpl src 192.168.2.100 dst 192.168.1.100 proto esp mode beet mark 0x00000001 mask 0x00000003 > > In fact, your case should use different priority to match. Sorry, but it does match your above policies now, like in xfrm_policy_match(), when fl->flowi_mark == 0x1234567b:
(fl->flowi_mark & pol->mark.m) != pol->mark.v 0x1234567b & 0x00000005 == 0x00000001
and when fl->flowi_mark == 0x1234567d: 0x1234567d & 0x00000003 == 0x00000001
am I missing something?
> > > > > I'm actually confused now. > > does the mask work against its own value, or the other value? > > as 'A == (mark.v&mark.m)' and '(A & mark.m) == mark.v' are different things. > > > > This can date back to Jamal's xfrm by MARK: > > > > https://lwn.net/Articles/375829/ > > > > where it does 'm->v & m->m' in xfrm_mark_get() and > > 'policy->mark.v & policy->mark.m' in xfrm_policy_insert() while > > it does '(A & pol->mark.m) == pol->mark.v' in other places. > > > > Now I'm thinking 'm->v & m->m' is meaningless, by which if we get > > a value != m->v, it means this mark can never be matched by any. > > > > policy A (mark.v = 1, mark.m = 0, priority = 1) > > policy B (mark.v = 1, mark.m = 0, priority = 1) > > > > So probably we should avoid this case by check m->v == (m->v & m->m) > > when adding a new policy. > > > > wdyt? > > >
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