From: Paolo Abeni <pabeni@redhat.com>
To: Weiming Shi <bestswngs@gmail.com>,
jhs@mojatatu.com, vinicius.gomes@intel.com, jiri@resnulli.us,
davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
shuah@kernel.org
Cc: horms@kernel.org, vladimir.oltean@nxp.com, xmei5@asu.edu,
netdev@vger.kernel.org, linux-kselftest@vger.kernel.org
Subject: Re: [PATCH net v4 1/2] net/sched: taprio: fix NULL pointer dereference in class dump
Date: Tue, 21 Apr 2026 10:49:12 +0200 [thread overview]
Message-ID: <d306bbeb-141c-4a44-bcc0-2e2c5d51efd5@redhat.com> (raw)
In-Reply-To: <20260416185501.647884-3-bestswngs@gmail.com>
On 4/16/26 8:55 PM, Weiming Shi wrote:
> @@ -2196,14 +2199,14 @@ static int taprio_graft(struct Qdisc *sch, unsigned long cl,
> *old = q->qdiscs[cl - 1];
> if (FULL_OFFLOAD_IS_ENABLED(q->flags)) {
> WARN_ON_ONCE(dev_graft_qdisc(dev_queue, new) != *old);
> - if (new)
> + if (new != &noop_qdisc)
> qdisc_refcount_inc(new);
> if (*old)
> qdisc_put(*old);
Unless I'm lost, it looks like taprio_leaf() can now return
`noop_qdisc`. As a consequence, `old` can be a valid qdisc, NULL or even
`noop_qdisc`. In the latter case it should not decrease the refcount, as
it was not increased previously.
/P
next prev parent reply other threads:[~2026-04-21 8:49 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-16 18:55 [PATCH net v4 0/2] net/sched: taprio: fix NULL pointer dereference in class dump Weiming Shi
2026-04-16 18:55 ` [PATCH net v4 1/2] " Weiming Shi
2026-04-21 8:49 ` Paolo Abeni [this message]
2026-04-16 18:55 ` [PATCH net v4 2/2] selftests/tc-testing: add taprio test for class dump after child delete Weiming Shi
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