netdev - [PATCH] net/sched: initialize noop

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Message-ID: <20240607175340.786bfb938803.I493bf8422e36be4454c08880a8d3703cea8e421a@changeid>
Date: Fri,  7 Jun 2024 17:53:32 +0200
From: Johannes Berg <johannes@...solutions.net>
To: netdev@...r.kernel.org
Cc: Johannes Berg <johannes.berg@...el.com>
Subject: [PATCH] net/sched: initialize noop_qdisc owner

From: Johannes Berg <johannes.berg@...el.com>

When the noop_qdisc owner isn't initialized, then it will be 0,
so packets will erroneously be regarded as having been subject
to recursion as long as only CPU 0 queues them. For non-SMP,
that's all packets, of course. This causes a change in what's
reported to userspace, normally noop_qdisc would drop packets
silently, but with this change the syscall returns -ENOBUFS if
RECVERR is also set on the socket.

Fix this by initializing the owner field to -1, just like it
would be for dynamically allocated qdiscs by qdisc_alloc().

Fixes: 0f022d32c3ec ("net/sched: Fix mirred deadlock on device recursion")
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
---
 net/sched/sch_generic.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index d3f6006b563c..fb32984d7a16 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -673,6 +673,7 @@ struct Qdisc noop_qdisc = {
 		.qlen = 0,
 		.lock = __SPIN_LOCK_UNLOCKED(noop_qdisc.skb_bad_txq.lock),
 	},
+	.owner = -1,
 };
 EXPORT_SYMBOL(noop_qdisc);

-- 
2.45.2