Message-Id: <879EA0B7-F334-4A17-92D5-166F627BEE6F@flyingcircus.io>
Date: Fri, 6 Oct 2023 11:07:50 +0200
From: Christian Theune <ct@...ingcircus.io>
To: Linux regressions mailing list <regressions@...ts.linux.dev>
Cc: stable@...r.kernel.org,
 netdev@...r.kernel.org,
 davem@...emloft.net,
 edumazet@...gle.com,
 kuba@...nel.org,
 pabeni@...hat.com
Subject: Re: [REGRESSION] Userland interface breaks due to hard HFSC_FSC
 requirement

Hi,

it seems that 6.6rc4 is affected as well:

----
commit b3d26c5702c7d6c45456326e56d2ccf3f103e60f
Author: Budimir Markovic <markovicbudimir@...il.com>
Date:   Thu Aug 24 01:49:05 2023 -0700

    net/sched: sch_hfsc: Ensure inner classes have fsc curve
——

I have not found newer commits that would suggest they change any behaviour around this in any way, but I might be wrong.

Christian

> On 6. Oct 2023, at 11:01, Linux regression tracking (Thorsten Leemhuis) <regressions@...mhuis.info> wrote:
> 
> On 06.10.23 10:37, Christian Theune wrote:
>> 
>> (prefix, I was not aware of the regression reporting process and incorrectly reported this informally with the developers mentioned in the change)
> 
> Don't worry too much about that, but thx for taking care of all the
> details. FWIW, there is one more thing that would be good to know:
> 
> Does the problem happen with mainline (e.g. 6.6-rc4) as well? That's
> relevant, as different people might care[1].
> 
> Ciao, Thorsten
> 
> [1] this among others is explained here:
> https://linux-regtracking.leemhuis.info/post/frequent-reasons-why-linux-kernel-bug-reports-are-ignored/
> 
>> I upgraded from 6.1.38 to 6.1.55 this morning and it broke my traffic shaping script, leaving me with a non-functional uplink on a remote router.
>> 
>> The script errors out like this:
>> 
>> Oct 06 05:49:22 wendy00 isp-setup-shaping-start[2053]: + ext=ispA
>> Oct 06 05:49:22 wendy00 isp-setup-shaping-start[2053]: + ext_ingress=ifb0
>> Oct 06 05:49:22 wendy00 isp-setup-shaping-start[2053]: + modprobe ifb
>> Oct 06 05:49:22 wendy00 isp-setup-shaping-start[2053]: + modprobe act_mirred
>> Oct 06 05:49:22 wendy00 isp-setup-shaping-start[2053]: + tc qdisc del dev ispA root
>> Oct 06 05:49:22 wendy00 isp-setup-shaping-start[2061]: Error: Cannot delete qdisc with handle of zero.
>> Oct 06 05:49:22 wendy00 isp-setup-shaping-start[2053]: + true
>> Oct 06 05:49:22 wendy00 isp-setup-shaping-start[2053]: + tc qdisc del dev ispA ingress
>> Oct 06 05:49:22 wendy00 isp-setup-shaping-start[2064]: Error: Cannot find specified qdisc on specified device.
>> Oct 06 05:49:22 wendy00 isp-setup-shaping-start[2053]: + true
>> Oct 06 05:49:22 wendy00 isp-setup-shaping-start[2053]: + tc qdisc del dev ifb0 root
>> Oct 06 05:49:22 wendy00 isp-setup-shaping-start[2066]: Error: Cannot delete qdisc with handle of zero.
>> Oct 06 05:49:22 wendy00 isp-setup-shaping-start[2053]: + true
>> Oct 06 05:49:22 wendy00 isp-setup-shaping-start[2053]: + tc qdisc del dev ifb0 ingress
>> Oct 06 05:49:22 wendy00 isp-setup-shaping-start[2067]: Error: Cannot find specified qdisc on specified device.
>> Oct 06 05:49:22 wendy00 isp-setup-shaping-start[2053]: + true
>> Oct 06 05:49:22 wendy00 isp-setup-shaping-start[2053]: + tc qdisc add dev ispA handle ffff: ingress
>> Oct 06 05:49:22 wendy00 isp-setup-shaping-start[2053]: + ifconfig ifb0 up
>> Oct 06 05:49:22 wendy00 isp-setup-shaping-start[2053]: + tc filter add dev ispA parent ffff: protocol all u32 match u32 0 0 action mirred egress redirect dev ifb0
>> Oct 06 05:49:22 wendy00 isp-setup-shaping-start[2053]: + tc qdisc add dev ifb0 root handle 1: hfsc default 1
>> Oct 06 05:49:22 wendy00 isp-setup-shaping-start[2053]: + tc class add dev ifb0 parent 1: classid 1:999 hfsc rt m2 2.5gbit
>> Oct 06 05:49:22 wendy00 isp-setup-shaping-start[2053]: + tc class add dev ifb0 parent 1:999 classid 1:1 hfsc sc rate 50mbit
>> Oct 06 05:49:22 wendy00 isp-setup-shaping-start[2077]: Error: Invalid parent - parent class must have FSC.
>> 
>> The error message is also a bit weird (but that’s likely due to iproute2 being weird) as the CLI interface for `tc` and the error message do not map well. (I think I would have to choose `hfsc sc` on the parent to enable the FSC option which isn’t mentioned anywhere in the hfsc manpage).
>> 
>> The breaking change was introduced in 6.1.53[1] and a multitude of other currently supported kernels:
>> 
>> ----
>> commit a1e820fc7808e42b990d224f40e9b4895503ac40
>> Author: Budimir Markovic <markovicbudimir@...il.com>
>> Date: Thu Aug 24 01:49:05 2023 -0700
>> 
>> net/sched: sch_hfsc: Ensure inner classes have fsc curve
>> 
>> [ Upstream commit b3d26c5702c7d6c45456326e56d2ccf3f103e60f ]
>> 
>> HFSC assumes that inner classes have an fsc curve, but it is currently
>> possible for classes without an fsc curve to become parents. This leads
>> to bugs including a use-after-free.
>> 
>> Don't allow non-root classes without HFSC_FSC to become parents.
>> 
>> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
>> Reported-by: Budimir Markovic <markovicbudimir@...il.com>
>> Signed-off-by: Budimir Markovic <markovicbudimir@...il.com>
>> Acked-by: Jamal Hadi Salim <jhs@...atatu.com>
>> Link: https://lore.kernel.org/r/20230824084905.422-1-markovicbudimir@gmail.com
>> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
>> Signed-off-by: Sasha Levin <sashal@...nel.org>
>> ----
>> 
>> Regards,
>> Christian
>> 
>> [1] https://cdn.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.1.53
>> 
>> #regzbot introduced: a1e820fc7808e42b990d224f40e9b4895503ac40
>> 
>> 

Liebe Grüße,
Christian Theune

-- 
Christian Theune · ct@...ingcircus.io · +49 345 219401 0
Flying Circus Internet Operations GmbH · https://flyingcircus.io
Leipziger Str. 70/71 · 06108 Halle (Saale) · Deutschland
HR Stendal HRB 21169 · Geschäftsführer: Christian Theune, Christian Zagrodnick

Powered by blists - more mailing lists