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Message-ID: <ZfLi17TuJpcd6KFb@nanopsycho>
Date: Thu, 14 Mar 2024 12:43:19 +0100
From: Jiri Pirko <jiri@...nulli.us>
To: renmingshuai <renmingshuai@...wei.com>
Cc: jhs@...atatu.com, xiyou.wangcong@...il.com, davem@...emloft.net,
vladbu@...dia.com, netdev@...r.kernel.org, yanan@...wei.com,
liaichun@...wei.com, caowangbao@...wei.com
Subject: Re: [PATCH] net/sched: Forbid assigning mirred action to a filter
attached to the egress
Thu, Mar 14, 2024 at 12:17:13PM CET, renmingshuai@...wei.com wrote:
>As we all know the mirred action is used to mirroring or redirecting the
>packet it receives. Howerver, add mirred action to a filter attached to
>a egress qdisc might cause a deadlock. To reproduce the problem, perform
>the following steps:
>(1)tc qdisc add dev eth0 root handle 1: htb default 30 \n
>(2)tc filter add dev eth2 protocol ip prio 2 flower verbose \
> action police rate 100mbit burst 12m conform-exceed jump 1 \
> / pipe mirred egress redirect dev eth2 action drop
>
>The stack is show as below:
>[28848.883915] _raw_spin_lock+0x1e/0x30
>[28848.884367] __dev_queue_xmit+0x160/0x850
>[28848.884851] ? 0xffffffffc031906a
>[28848.885279] tcf_mirred_act+0x3ab/0x596 [act_mirred]
>[28848.885863] tcf_action_exec.part.0+0x88/0x130
>[28848.886401] fl_classify+0x1ca/0x1e0 [cls_flower]
>[28848.886970] ? dequeue_entity+0x145/0x9e0
>[28848.887464] ? newidle_balance+0x23f/0x2f0
>[28848.887973] ? nft_lookup_eval+0x57/0x170 [nf_tables]
>[28848.888566] ? nft_do_chain+0xef/0x430 [nf_tables]
>[28848.889137] ? __flush_work.isra.0+0x35/0x80
>[28848.889657] ? nf_ct_get_tuple+0x1cf/0x210 [nf_conntrack]
>[28848.890293] ? do_select+0x637/0x870
>[28848.890735] tcf_classify+0x52/0xf0
>[28848.891177] htb_classify+0x9d/0x1c0 [sch_htb]
>[28848.891722] htb_enqueue+0x3a/0x1c0 [sch_htb]
>[28848.892251] __dev_queue_xmit+0x2d8/0x850
>[28848.892738] ? nf_hook_slow+0x3c/0xb0
>[28848.893198] ip_finish_output2+0x272/0x580
>[28848.893692] __ip_queue_xmit+0x193/0x420
>[28848.894179] __tcp_transmit_skb+0x8cc/0x970
>
>In this case, the process has hold the qdisc spin lock in __dev_queue_xmit
>before the egress packets are mirred, and it will attempt to obtain the
>spin lock again after packets are mirred, which cause a deadlock.
>
>Fix the issue by forbidding assigning mirred action to a filter attached
>to the egress.
>
>Signed-off-by: Mingshuai Ren <renmingshuai@...wei.com>
You are missing "Fixes" tag.
>---
> net/sched/act_mirred.c | 4 +++
> .../tc-testing/tc-tests/actions/mirred.json | 32 +++++++++++++++++++
> 2 files changed, 36 insertions(+)
>
>diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c
>index 5b3814365924..fc96705285fb 100644
>--- a/net/sched/act_mirred.c
>+++ b/net/sched/act_mirred.c
>@@ -120,6 +120,10 @@ static int tcf_mirred_init(struct net *net, struct nlattr *nla,
> NL_SET_ERR_MSG_MOD(extack, "Mirred requires attributes to be passed");
> return -EINVAL;
> }
>+ if (tp->chain->block->q->parent != TC_H_INGRESS) {
>+ NL_SET_ERR_MSG_MOD(extack, "Mirred can only be assigned to the filter attached to ingress");
Hmm, that is quite restrictive. I'm pretty sure you would break some
valid usecases.
>+ return -EINVAL;
>+ }
> ret = nla_parse_nested_deprecated(tb, TCA_MIRRED_MAX, nla,
> mirred_policy, extack);
> if (ret < 0)
>diff --git a/tools/testing/selftests/tc-testing/tc-tests/actions/mirred.json b/tools/testing/selftests/tc-testing/tc-tests/actions/mirred.json
>index b73bd255ea36..50c6153bf34c 100644
>--- a/tools/testing/selftests/tc-testing/tc-tests/actions/mirred.json
>+++ b/tools/testing/selftests/tc-testing/tc-tests/actions/mirred.json
>@@ -1052,5 +1052,37 @@
> "$TC qdisc del dev $DEV1 ingress_block 21 clsact",
> "$TC actions flush action mirred"
> ]
>+ },
>+ {
>+ "id": "fdda",
>+ "name": "Add mirred mirror to the filter which attached to engress",
>+ "category": [
>+ "actions",
>+ "mirred"
>+ ],
>+ "plugins": {
>+ "requires": "nsPlugin"
>+ },
>+ "setup": [
>+ [
>+ "$TC actions flush action mirred",
>+ 0,
>+ 1,
>+ 255
>+ ],
>+ [
>+ "$TC qdisc add dev $DEV1 root handle 1: htb default 1",
>+ 0
>+ ]
>+ ],
>+ "cmdUnderTest": "$TC filter add dev $DEV1 protocol ip u32 match ip protocol 1 0xff action mirred egress mirror dev $DEV1",
>+ "expExitCode": "2",
>+ "verifyCmd": "$TC action list action mirred",
>+ "matchPattern": "^[ \t]+index [0-9]+ ref",
>+ "matchCount": "0",
>+ "teardown": [
>+ "$TC qdisc del dev $DEV1 root handle 1: htb default 1",
>+ "$TC actions flush action mirred"
>+ ]
> }
> ]
>--
>2.33.0
>
>
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