From: Budimir Markovic <markovicbudimir@gmail.com>
Date: Thu, 24 Aug 2023 01:49:05 -0700
Subject: net/sched: sch_hfsc: Ensure inner classes have fsc curve
Patch-mainline: v6.6-rc1
Git-commit: b3d26c5702c7d6c45456326e56d2ccf3f103e60f
References: CVE-2023-4623 bsc#1215115

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.

SLE: not all 4.12 based branches have extack available in
hfsc_change_class(), omit setting the extack error message.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: Budimir Markovic <markovicbudimir@gmail.com>
Signed-off-by: Budimir Markovic <markovicbudimir@gmail.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Link: https://lore.kernel.org/r/20230824084905.422-1-markovicbudimir@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Michal Kubecek <mkubecek@suse.cz>

---
 net/sched/sch_hfsc.c | 2 ++
 1 file changed, 2 insertions(+)

--- a/net/sched/sch_hfsc.c
+++ b/net/sched/sch_hfsc.c
@@ -1053,6 +1053,8 @@ hfsc_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
 		if (parent == NULL)
 			return -ENOENT;
 	}
+	if (!(parent->cl_flags & HFSC_FSC) && parent != &q->root)
+		return -EINVAL;
 
 	if (classid == 0 || TC_H_MAJ(classid ^ sch->handle) != 0)
 		return -EINVAL;