[PATCH 4.14] net/sched: sch_hfsc: Ensure inner classes have fsc curve

[Shaoying Xu <shaoyi@amazon.com>]

From: Budimir Markovic <markovicbudimir@gmail.com>

[ Upstream commit b3d26c5702c7d6c45456326e56d2ccf3f103e60f ]

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.

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>
[ v4.14: Delete NL_SET_ERR_MSG because extack is not added to hfsc_change_class ]
Cc: <stable@vger.kernel.org> # 4.14 
Signed-off-by: Shaoying Xu <shaoyi@amazon.com>
---
 net/sched/sch_hfsc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/sched/sch_hfsc.c b/net/sched/sch_hfsc.c
index 3f88b75488b0..3a43abe4d9c4 100644
--- a/net/sched/sch_hfsc.c
+++ b/net/sched/sch_hfsc.c
@@ -1020,6 +1020,8 @@ 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;
-- 
2.40.1