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Date: Tue, 2 Jan 2024 09:52:01 -0500
From: Jamal Hadi Salim <jhs@...atatu.com>
To: Jiri Pirko <jiri@...nulli.us>
Cc: Victor Nogueira <victor@...atatu.com>, davem@...emloft.net, edumazet@...gle.com,
kuba@...nel.org, pabeni@...hat.com, xiyou.wangcong@...il.com,
idosch@...sch.org, mleitner@...hat.com, vladbu@...dia.com, paulb@...dia.com,
pctammela@...atatu.com, netdev@...r.kernel.org, kernel@...atatu.com,
syzbot+84339b9e7330daae4d66@...kaller.appspotmail.com,
syzbot+806b0572c8d06b66b234@...kaller.appspotmail.com,
syzbot+0039110f932d438130f9@...kaller.appspotmail.com
Subject: Re: [PATCH net-next v2 1/1] net/sched: We should only add appropriate
qdiscs blocks to ports' xarray
On Tue, Jan 2, 2024 at 9:29 AM Jiri Pirko <jiri@...nulli.us> wrote:
>
> Tue, Jan 02, 2024 at 03:06:28PM CET, jhs@...atatu.com wrote:
> >On Tue, Jan 2, 2024 at 4:59 AM Jiri Pirko <jiri@...nulli.us> wrote:
> >>
> >> The patch subject should briefly describe the nature of the change. Not
> >> what "we" should or should not do.
> >>
> >>
> >> Sun, Dec 31, 2023 at 06:23:20PM CET, victor@...atatu.com wrote:
> >> >We should only add qdiscs to the blocks ports' xarray in ingress that
> >> >support ingress_block_set/get or in egress that support
> >> >egress_block_set/get.
> >>
> >> Tell the codebase what to do, be imperative. Please read again:
> >> https://www.kernel.org/doc/html/v6.6/process/submitting-patches.html#describe-your-changes
> >>
> >
> >We need another rule in the doc on nit-picking which states that we
> >need to make progress at some point. We made many changes to this
> >patchset based on your suggestions for no other reason other that we
> >can progress the discussion. This is a patch that fixes a bug of which
> >there are multiple syzbot reports and consumers of the API(last one
> >just reported from the MTCP people). There's some sense of urgency to
> >apply this patch before the original goes into net. More importantly:
> >This patch fixes the issue and follows the same common check which was
> >already being done in the committed patchset to check if the qdisc
> >supports the block set/get operations.
> >
> >There are about 3 ways to do this check, you objected to the original,
> >we picked something that works fine, and now you are picking a
> >different way with tcf_block. I dont see how tcf_block check would
> >help or solve this problem at all given this is a qdisc issue not a
> >class issue. What am I missing?
>
> Perhaps I got something wrong, but I thought that the issue is
> cl_ops->tcf_block being null for some qdiscs, isn't it?
>
We attach these ports/netdevs only on capable qdiscs i.e ones that
have in/egress_block_set/get() - which happen to be ingress and
clsact only.
The problem was we were blindly assuming that presence of
cl->tcf_block() implies presence of in/egress_block_set/get(). The
earlier patches surrounded this code with attribute checks and so it
worked there.
BTW: Do you have an example of a test case where we can test the class
grafting (eg using htb with tcf_block)? It doesnt have any impact on
this patcheset here but we want to add it as a regression checker on
tdc in the future if someone makes a change.
cheers,
jamal
> >
> >cheers,
> >jamal
> >
> >> >
> >> >Fixes: 913b47d3424e ("net/sched: Introduce tc block netdev tracking infra")
> >> >Signed-off-by: Victor Nogueira <victor@...atatu.com>
> >> >Reviewed-by: Jamal Hadi Salim <jhs@...atatu.com>
> >> >Reported-by: Ido Schimmel <idosch@...dia.com>
> >> >Closes: https://lore.kernel.org/all/ZY1hBb8GFwycfgvd@shredder/
> >> >Tested-by: Ido Schimmel <idosch@...dia.com>
> >> >Reported-and-tested-by: syzbot+84339b9e7330daae4d66@...kaller.appspotmail.com
> >> >Closes: https://lore.kernel.org/all/0000000000007c85f5060dcc3a28@google.com/
> >> >Reported-and-tested-by: syzbot+806b0572c8d06b66b234@...kaller.appspotmail.com
> >> >Closes: https://lore.kernel.org/all/00000000000082f2f2060dcc3a92@google.com/
> >> >Reported-and-tested-by: syzbot+0039110f932d438130f9@...kaller.appspotmail.com
> >> >Closes: https://lore.kernel.org/all/0000000000007fbc8c060dcc3a5c@google.com/
> >> >---
> >> >v1 -> v2:
> >> >
> >> >- Remove newline between fixes tag and Signed-off-by tag
> >> >- Add Ido's Reported-by and Tested-by tags
> >> >- Add syzbot's Reported-and-tested-by tags
> >> >
> >> > net/sched/sch_api.c | 34 ++++++++++++++++++++--------------
> >> > 1 file changed, 20 insertions(+), 14 deletions(-)
> >> >
> >> >diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
> >> >index 299086bb6205..426be81276f1 100644
> >> >--- a/net/sched/sch_api.c
> >> >+++ b/net/sched/sch_api.c
> >> >@@ -1187,23 +1187,29 @@ static int qdisc_block_add_dev(struct Qdisc *sch, struct net_device *dev,
> >> > struct tcf_block *block;
> >> > int err;
> >> >
> >>
> >> Why don't you just check cl_ops->tcf_block ?
> >> In fact, there could be a helper to do it for you either call the op or
> >> return NULL in case it is not defined.
> >>
> >>
> >> >- block = cl_ops->tcf_block(sch, TC_H_MIN_INGRESS, NULL);
> >> >- if (block) {
> >> >- err = xa_insert(&block->ports, dev->ifindex, dev, GFP_KERNEL);
> >> >- if (err) {
> >> >- NL_SET_ERR_MSG(extack,
> >> >- "ingress block dev insert failed");
> >> >- return err;
> >> >+ if (sch->ops->ingress_block_get) {
> >> >+ block = cl_ops->tcf_block(sch, TC_H_MIN_INGRESS, NULL);
> >> >+ if (block) {
> >> >+ err = xa_insert(&block->ports, dev->ifindex, dev,
> >> >+ GFP_KERNEL);
> >> >+ if (err) {
> >> >+ NL_SET_ERR_MSG(extack,
> >> >+ "ingress block dev insert failed");
> >> >+ return err;
> >> >+ }
> >> > }
> >> > }
> >> >
> >> >- block = cl_ops->tcf_block(sch, TC_H_MIN_EGRESS, NULL);
> >> >- if (block) {
> >> >- err = xa_insert(&block->ports, dev->ifindex, dev, GFP_KERNEL);
> >> >- if (err) {
> >> >- NL_SET_ERR_MSG(extack,
> >> >- "Egress block dev insert failed");
> >> >- goto err_out;
> >> >+ if (sch->ops->egress_block_get) {
> >> >+ block = cl_ops->tcf_block(sch, TC_H_MIN_EGRESS, NULL);
> >> >+ if (block) {
> >> >+ err = xa_insert(&block->ports, dev->ifindex, dev,
> >> >+ GFP_KERNEL);
> >> >+ if (err) {
> >> >+ NL_SET_ERR_MSG(extack,
> >> >+ "Egress block dev insert failed");
> >> >+ goto err_out;
> >> >+ }
> >> > }
> >> > }
> >> >
> >> >--
> >> >2.25.1
> >> >
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