[PATCH v3] net/sched: Set the flushing flags to false to prevent an infinite loop and add one test to tdc
From: renmingshuai
Date: Thu Jun 08 2023 - 23:31:57 EST
>On 08/06/2023 09:32, renmingshuai wrote:
>>> On 07/06/2023 01:19, renmingshuai wrote:
>>>>> On 06/06/2023 11:45, renmingshuai wrote:
>>>>>> When a new chain is added by using tc, one soft lockup alarm will
>>>>>> be
>>>>>> generated after delete the prio 0 filter of the chain. To
>>>>>> reproduce
>>>>>> the problem, perform the following steps:
>>>>>> (1) tc qdisc add dev eth0 root handle 1: htb default 1
>>>>>> (2) tc chain add dev eth0
>>>>>> (3) tc filter del dev eth0 chain 0 parent 1: prio 0
>>>>>> (4) tc filter add dev eth0 chain 0 parent 1:
>>>>>
>>>>> This seems like it could be added to tdc or 3 and 4 must be run in
>>>>> parallel?
>>>> 3 and 4 do not need to be run inparallel. When a new chain is added
>>>> by the
>>>> way as step 1 and the step 3 is completed, this problem always
>>>> occurs
>>>> whenever step 4 is run.
>>>
>>> Got it,
>>> The test still hangs with the provided patch.
>>>
>>> + tc qdisc add dev lo root handle 1: htb default 1
>>> + tc chain add dev lo
>>> + tc filter del dev lo chain 0 parent 1: prio 0
>>> [ 68.790030][ T6704] [+]
>>> [ 68.790060][ T6704] chain refcnt 2
>>> [ 68.790951][ T6704] [-]
>>> + tc filter add dev lo chain 0 parent 1:
>>> <hangs>
>>>
>>> Also please add this test to tdc, it should be straightforward.
>>>
>> Sorry for not testing before. I forgot that the chain->refcnt was
>> increased by 1 when tcf_chain_get() is called in tc_del_tfilter().
>> The value of chain->refcnt is 2 after chain flush. The test
>> result is as follows:
>> [root@localhost ~]# tc qdisc add dev eth2 root handle 1: htb default 1
>> [root@localhost ~]# tc chain add dev eth2
>> [root@localhost ~]# tc filter del dev eth2 chain 0 parent 1: prio 0
>> [root@localhost ~]# tc filter add dev eth2 chain 0 parent 1:
>> Error: Filter kind and protocol must be specified.
>> We have an error talking to the kernel
>>
>> And I have add this test to tdc:
>> [root@localhost tc-testing]# ./tdc.py -f tc-tests/filters/tests.json
>> ok 7 c2b4 - Adding a new fiter after deleting a filter in a chain does
>> not cause an infinite loop
>>
>> Fixes: 726d061286ce ("net: sched: prevent insertion of new classifiers during chain flush")
>> Signed-off-by: renmingshuai <renmingshuai@xxxxxxxxxx>
>
>Please respin with the following applied:
>
>diff --git
>a/tools/testing/selftests/tc-testing/tc-tests/filters/tests.json
>b/tools/testing/selftests/tc-testing/tc-tests/filters/tests.json
>index c759c3db9a37..361235ad574b 100644
>--- a/tools/testing/selftests/tc-testing/tc-tests/filters/tests.json
>+++ b/tools/testing/selftests/tc-testing/tc-tests/filters/tests.json
>@@ -125,25 +125,5 @@
> "teardown": [
> "$TC qdisc del dev $DEV2 ingress"
> ]
>- },
>- {
>- "id": "c2b4",
>- "name": "Adding a new fiter after deleting a filter in a chain
>does not cause an infinite loop",
>- "category": [
>- "filter",
>- "prio"
>- ],
>- "setup": [
>- "$TC qdisc add dev $DEV1 root handle 1: htb default 1",
>- "$TC chain add dev $DEV1"
>- ],
>- "cmdUnderTest": "$TC filter del dev $DEV1 chain 0 parent 1:
>prio 0",
>- "expExitCode": "0",
>- "verifyCmd": "$TC filter add dev $DEV1 chain 0 parent 1:",
>- "matchPattern": "Error: Filter kind and protocol must be
>specified.",
>- "matchCount": "1",
>- "teardown": [
>- "$TC qdisc del dev $DEV1 root handle 1: htb default 1"
>- ]
> }
> ]
>diff --git
>a/tools/testing/selftests/tc-testing/tc-tests/infra/filters.json
>b/tools/testing/selftests/tc-testing/tc-tests/infra/filters.
>json
>new file mode 100644
>index 000000000000..55d6f209c388
>--- /dev/null
>+++ b/tools/testing/selftests/tc-testing/tc-tests/infra/filters.json
>@@ -0,0 +1,24 @@
>+[
>+ {
>+ "id": "c2b4",
>+ "name": "Adding a new filter after flushing empty chain doesnt
>cause an infinite loop",
>+ "category": [
>+ "filter",
>+ "chain"
>+ ],
>+ "setup": [
>+ "$IP link add dev $DUMMY type dummy || /bin/true",
>+ "$TC qdisc add dev $DUMMY root handle 1: htb default 1",
>+ "$TC chain add dev $DUMMY",
>+ "$TC filter del dev $DUMMY chain 0 parent 1: prio 0"
>+ ],
>+ "cmdUnderTest": "$TC filter add dev $DUMMY chain 0 parent 1:",
>+ "expExitCode": "2",
>+ "verifyCmd": "$TC chain ls dev $DUMMY",
>+ "matchPattern": "chain parent 1: chain 0",
>+ "matchCount": "1",
>+ "teardown": [
>+ "$TC qdisc del dev $DUMMY root handle 1: htb default 1"
>+ ]
>+ }
>+]
Ok. The new test is passed.
[root@localhost tc-testing]# ./tdc.py -f tc-tests/infra/filter.json
Test c2b4: Adding a new filter after flushing empty chain doesn't cause an infinite loop
All test results:
1..1
ok 1 c2b4 - Adding a new filter after flushing empty chain doesn't cause an infinite loop
Fixes: 726d061286ce ("net: sched: prevent insertion of new classifiers during chain flush")
Signed-off-by: renmingshuai <renmingshuai@xxxxxxxxxx>
---
net/sched/cls_api.c | 7 ++++++
.../tc-testing/tc-tests/infra/filter.json | 25 +++++++++++++++++++
2 files changed, 32 insertions(+)
create mode 100644 tools/testing/selftests/tc-testing/tc-tests/infra/filter.json
diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index 2621550bfddc..3ea054e03fbf 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -2442,6 +2442,13 @@ static int tc_del_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
tfilter_notify_chain(net, skb, block, q, parent, n,
chain, RTM_DELTFILTER, extack);
tcf_chain_flush(chain, rtnl_held);
+ /* Set the flushing flags to false to prevent an infinite loop
+ * when a new filter is added.
+ */
+ mutex_lock(&chain->filter_chain_lock);
+ if (chain->refcnt == 2)
+ chain->flushing = false;
+ mutex_unlock(&chain->filter_chain_lock);
err = 0;
goto errout;
}
diff --git a/tools/testing/selftests/tc-testing/tc-tests/infra/filter.json b/tools/testing/selftests/tc-testing/tc-tests/infra/filter.json
new file mode 100644
index 000000000000..db3b42aaa4fa
--- /dev/null
+++ b/tools/testing/selftests/tc-testing/tc-tests/infra/filter.json
@@ -0,0 +1,25 @@
+[
+ {
+ "id": "c2b4",
+ "name": "Adding a new filter after flushing empty chain doesn't cause an infinite loop",
+ "category": [
+ "filter",
+ "chain"
+ ],
+ "setup": [
+ "$IP link add dev $DUMMY type dummy || /bin/true",
+ "$TC qdisc add dev $DUMMY root handle 1: htb default 1",
+ "$TC chain add dev $DUMMY",
+ "$TC filter del dev $DUMMY chain 0 parent 1: prio 0"
+ ],
+ "cmdUnderTest": "$TC filter add dev $DUMMY chain 0 parent 1:",
+ "expExitCode": "2",
+ "verifyCmd": "$TC chain ls dev $DUMMY",
+ "matchPattern": "chain parent 1: chain 0",
+ "matchCount": "1",
+ "teardown": [
+ "$TC qdisc del dev $DUMMY root handle 1: htb default 1",
+ "$IP link del dev $DUMMY type dummy"
+ ]
+ }
+]
--
2.27.0