This is a note to let you know that I've just added the patch titled
sch_api: Don't skip qdisc attach on ingress
to the 5.16-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sch_api-don-t-skip-qdisc-attach-on-ingress.patch
and it can be found in the queue-5.16 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From de2d807b294d3d2ce5e59043ae2634016765d076 Mon Sep 17 00:00:00 2001
From: Maxim Mikityanskiy <maximmi@xxxxxxxxxx>
Date: Wed, 12 Jan 2022 12:28:05 +0200
Subject: sch_api: Don't skip qdisc attach on ingress
From: Maxim Mikityanskiy <maximmi@xxxxxxxxxx>
commit de2d807b294d3d2ce5e59043ae2634016765d076 upstream.
The attach callback of struct Qdisc_ops is used by only a few qdiscs:
mq, mqprio and htb. qdisc_graft() contains the following logic
(pseudocode):
if (!qdisc->ops->attach) {
if (ingress)
do ingress stuff;
else
do egress stuff;
}
if (!ingress) {
...
if (qdisc->ops->attach)
qdisc->ops->attach(qdisc);
} else {
...
}
As we see, the attach callback is not called if the qdisc is being
attached to ingress (TC_H_INGRESS). That wasn't a problem for mq and
mqprio, since they contain a check that they are attached to TC_H_ROOT,
and they can't be attached to TC_H_INGRESS anyway.
However, the commit cited below added the attach callback to htb. It is
needed for the hardware offload, but in the non-offload mode it
simulates the "do egress stuff" part of the pseudocode above. The
problem is that when htb is attached to ingress, neither "do ingress
stuff" nor attach() is called. It results in an inconsistency, and the
following message is printed to dmesg:
unregister_netdevice: waiting for lo to become free. Usage count = 2
This commit addresses the issue by running "do ingress stuff" in the
ingress flow even in the attach callback is present, which is fine,
because attach isn't going to be called afterwards.
The bug was found by syzbot and reported by Eric.
Fixes: d03b195b5aa0 ("sch_htb: Hierarchical QoS hardware offload")
Signed-off-by: Maxim Mikityanskiy <maximmi@xxxxxxxxxx>
Reported-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/sched/sch_api.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -1062,7 +1062,7 @@ static int qdisc_graft(struct net_device
qdisc_offload_graft_root(dev, new, old, extack);
- if (new && new->ops->attach)
+ if (new && new->ops->attach && !ingress)
goto skip;
for (i = 0; i < num_q; i++) {
Patches currently in stable-queue which might be from maximmi@xxxxxxxxxx are
queue-5.16/bpf-fix-the-test_task_vma-selftest-to-support-output.patch
queue-5.16/sch_api-don-t-skip-qdisc-attach-on-ingress.patch
