5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Cong Wang xiyou.wangcong@gmail.com
[ Upstream commit 0c3057a5a04d07120b3d0ec9c79568fceb9c921e ]
The function qdisc_tree_reduce_backlog() uses TC_H_ROOT as a termination condition when traversing up the qdisc tree to update parent backlog counters. However, if a class is created with classid TC_H_ROOT, the traversal terminates prematurely at this class instead of reaching the actual root qdisc, causing parent statistics to be incorrectly maintained. In case of DRR, this could lead to a crash as reported by Mingi Cho.
Prevent the creation of any Qdisc class with classid TC_H_ROOT (0xFFFFFFFF) across all qdisc types, as suggested by Jamal.
Reported-by: Mingi Cho mincho@theori.io Signed-off-by: Cong Wang xiyou.wangcong@gmail.com Reviewed-by: Simon Horman horms@kernel.org Fixes: 066a3b5b2346 ("[NET_SCHED] sch_api: fix qdisc_tree_decrease_qlen() loop") Link: https://patch.msgid.link/20250306232355.93864-2-xiyou.wangcong@gmail.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/sched/sch_api.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c index 178044a845dfd..60c8b81a22dcd 100644 --- a/net/sched/sch_api.c +++ b/net/sched/sch_api.c @@ -2159,6 +2159,12 @@ static int tc_ctl_tclass(struct sk_buff *skb, struct nlmsghdr *n, return -EOPNOTSUPP; }
+ /* Prevent creation of traffic classes with classid TC_H_ROOT */ + if (clid == TC_H_ROOT) { + NL_SET_ERR_MSG(extack, "Cannot create traffic class with classid TC_H_ROOT"); + return -EINVAL; + } + new_cl = cl; err = -EOPNOTSUPP; if (cops->change)