diff options
| author | Zijie Huang <milkory@outlook.com> | 2026-08-01 21:42:33 +0800 |
|---|---|---|
| committer | Paolo Abeni <pabeni@redhat.com> | 2026-08-06 15:24:44 +0200 |
| commit | dedd34b0f2310e28c5f6d4875cfbf4b7ed821c01 (patch) | |
| tree | 0ccba782af4a99ebde5b0742667f644666834607 | |
| parent | 7e2d693af0d4c05bddccb3541a0aabd69f4cb244 (diff) | |
net/sched: reject overly deep qdisc hierarchies
Deep qdisc hierarchies can lead to excessive recursion in qdisc tree
walkers and exhaust the kernel stack. The existing loop check does not
cover the create-and-graft path, so a hierarchy can still be extended by
creating a new child qdisc below an already deep parent.
Store the hierarchy depth in struct Qdisc and update it when qdiscs are
grafted. Reject new child qdiscs once the parent is already at the maximum
allowed depth.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Suggested-by: Jamal Hadi Salim <jhs@mojatatu.com>
Reported-by: Vega <vega@nebusec.ai>
Assisted-by: Codex:gpt-5.4
Signed-off-by: Zijie Huang <milkory@outlook.com>
Signed-off-by: Ren Wei <enjou1224z@gmail.com>
Reviewed-by: Victor Nogueira <victor@mojatatu.com>
Link: https://patch.msgid.link/1e9ab39597423fd5d13cfaaf52279b8ee3d9fc3c.1785434373.git.milkory@outlook.com
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
| -rw-r--r-- | include/net/sch_generic.h | 1 | ||||
| -rw-r--r-- | net/sched/sch_api.c | 9 |
2 files changed, 10 insertions, 0 deletions
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h index 45a1e8c78222..cbc248776511 100644 --- a/include/net/sch_generic.h +++ b/include/net/sch_generic.h @@ -99,6 +99,7 @@ struct Qdisc { struct hlist_node hash; u32 handle; u32 parent; + int depth; struct netdev_queue *dev_queue; diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c index 668bcd60d183..65b35528d125 100644 --- a/net/sched/sch_api.c +++ b/net/sched/sch_api.c @@ -1114,6 +1114,9 @@ static int qdisc_graft(struct net_device *dev, struct Qdisc *parent, unsigned int i, num_q, ingress; struct netdev_queue *dev_queue; + if (new) + new->depth = 0; + ingress = 0; num_q = dev->num_tx_queues; if ((q && q->flags & TCQ_F_INGRESS) || @@ -1211,9 +1214,15 @@ skip: NL_SET_ERR_MSG(extack, "STAB not supported on a non root"); return -EINVAL; } + if (new && parent->depth >= 7) { + NL_SET_ERR_MSG(extack, "Qdisc hierarchy is too deep"); + return -E2BIG; + } err = cops->graft(parent, cl, new, &old, extack); if (err) return err; + if (new) + new->depth = parent->depth + 1; notify_and_destroy(net, skb, n, classid, old, new, extack); } return 0; |