[PATCH 5.6 023/194] net_sched: fix tcm_parent in tc filter dump

Greg Kroah-Hartman
2020-05-18T18:14:36Z

From: Cong Wang <xiyou.wangcong@gmail.com>

[ Upstream commit a7df4870d79b00742da6cc93ca2f336a71db77f7 ]

When we tell kernel to dump filters from root (ffff:ffff),
those filters on ingress (ffff:0000) are matched, but their
true parents must be dumped as they are. However, kernel
dumps just whatever we tell it, that is either ffff:ffff
or ffff:0000:

$ nl-cls-list --dev=dummy0 --parent=root
cls basic dev dummy0 id none parent root prio 49152 protocol ip match-all
cls basic dev dummy0 id :1 parent root prio 49152 protocol ip match-all
$ nl-cls-list --dev=dummy0 --parent=ffff:
cls basic dev dummy0 id none parent ffff: prio 49152 protocol ip match-all
cls basic dev dummy0 id :1 parent ffff: prio 49152 protocol ip match-all

This is confusing and misleading, more importantly this is
a regression since 4.15, so the old behavior must be restored.

And, when tc filters are installed on a tc class, the parent
should be the classid, rather than the qdisc handle. Commit
edf6711c9840 ("net: sched: remove classid and q fields from tcf_proto")
removed the classid we save for filters, we can just restore
this classid in tcf_block.

Steps to reproduce this:
ip li set dev dummy0 up
tc qd add dev dummy0 ingress
tc filter add dev dummy0 parent ffff: protocol arp basic action pass
tc filter show dev dummy0 root

Before this patch:
filter protocol arp pref 49152 basic
filter protocol arp pref 49152 basic handle 0x1
action order 1: gact action pass
random type none pass val 0
index 1 ref 1 bind 1

After this patch:
filter parent ffff: protocol arp pref 49152 basic
filter parent ffff: protocol arp pref 49152 basic handle 0x1
action order 1: gact action pass
random type none pass val 0
index 1 ref 1 bind 1

Fixes: a10fa20101ae ("net: sched: propagate q and parent from caller down to tcf_fill_node")
Fixes: edf6711c9840 ("net: sched: remove classid and q fields from tcf_proto")
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/net/sch_generic.h | 1 +
net/sched/cls_api.c | 8 ++++----
2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index c30f914867e64..f1f8acb14b674 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -407,6 +407,7 @@ struct tcf_block {
struct mutex lock;
struct list_head chain_list;
u32 index; /* block index for shared blocks */
+ u32 classid; /* which class this block belongs to */
refcount_t refcnt;
struct net *net;
struct Qdisc *q;
diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index c2cdd0fc2e709..68c8fc6f535c7 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -2005,6 +2005,7 @@ static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
err = PTR_ERR(block);
goto errout;
}
+ block->classid = parent;

chain_index = tca[TCA_CHAIN] ? nla_get_u32(tca[TCA_CHAIN]) : 0;
if (chain_index > TC_ACT_EXT_VAL_MASK) {
@@ -2547,12 +2548,10 @@ static int tc_dump_tfilter(struct sk_buff *skb, struct netlink_callback *cb)
return skb->len;

parent = tcm->tcm_parent;
- if (!parent) {
+ if (!parent)
q = dev->qdisc;
- parent = q->handle;
- } else {
+ else
q = qdisc_lookup(dev, TC_H_MAJ(tcm->tcm_parent));
- }
if (!q)
goto out;
cops = q->ops->cl_ops;
@@ -2568,6 +2567,7 @@ static int tc_dump_tfilter(struct sk_buff *skb, struct netlink_callback *cb)
block = cops->tcf_block(q, cl, NULL);
if (!block)
goto out;
+ parent = block->classid;
if (tcf_block_shared(block))
q = NULL;
}
--
2.20.1