[PATCH 5.10.y] net/sched: reject overly deep qdisc hierarchies
Sasha Levin <[email protected]>
| Newsgroups | org.kernel.vger.stable |
|---|---|
| Message-ID | <[email protected]> |
From: Zijie Huang <[email protected]> [ Upstream commit dedd34b0f2310e28c5f6d4875cfbf4b7ed821c01 ] 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: [email protected] Suggested-by: Jamal Hadi Salim <[email protected]> Reported-by: Vega <[email protected]> Assisted-by: Codex:gpt-5.4 Signed-off-by: Zijie Huang <[email protected]> Signed-off-by: Ren Wei <[email protected]> Reviewed-by: Victor Nogueira <[email protected]> Link: https://patch.msgid.link/1e9ab39597423fd5d13cfaaf52279b8ee3d9fc3c.1785434373.git.milkory@outlook.com Acked-by: Jamal Hadi Salim <[email protected]> Signed-off-by: Paolo Abeni <[email protected]> [ Dropped the `extack` argument from the `notify_and_destroy()` context line to match 5.15's 6-parameter version. ] Signed-off-by: Sasha Levin <[email protected]> --- include/net/sch_generic.h | 1 + net/sched/sch_api.c | 9 +++++++++ 2 files changed, 10 insertions(+) diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h index a4c670ad8c4ac..b46a70602da44 100644 --- a/include/net/sch_generic.h +++ b/include/net/sch_generic.h @@ -86,6 +86,7 @@ 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 932c98b5b347e..9c90b54e46300 100644 --- a/net/sched/sch_api.c +++ b/net/sched/sch_api.c @@ -1031,6 +1031,9 @@ 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) || @@ -1110,9 +1113,15 @@ static int qdisc_graft(struct net_device *dev, struct Qdisc *parent, 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); } return 0; -- 2.53.0