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Message-ID: <CAM0EoMmqVHGC4_YVHj=rUPj+XBS_N99rCKk1S7wCi1wJ8__Pyw@mail.gmail.com>
Date: Thu, 14 Mar 2024 13:14:54 -0400
From: Jamal Hadi Salim <jhs@...atatu.com>
To: renmingshuai <renmingshuai@...wei.com>
Cc: xiyou.wangcong@...il.com, jiri@...nulli.us, 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
On Thu, Mar 14, 2024 at 7:18 AM renmingshuai <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
>
I think you meant both to be the same device eth0 or eth2?
> 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>
> ---
> 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");
> + return -EINVAL;
> + }
Sorry, this is too restrictive as Jiri said. We'll try to reproduce. I
am almost certain this used to work in the old days.
cheers,
jamal
PS:- thanks for the tdc test, you are a hero just for submitting that!
> 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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