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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Thorsten Glaser <tg@mirbsd.de>,
        Diederik de Haas <didi.debian@cknow.org>
Subject: [PATCH 4.19 48/49] net/sched: move NULL ptr check to qdisc_put() too
Date:   Thu, 30 Jun 2022 15:47:01 +0200
Message-Id: <20220630133235.289157437@linuxfoundation.org>
In-Reply-To: <20220630133233.910803744@linuxfoundation.org>
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From: Diederik de Haas <didi.debian@cknow.org>

In commit 92833e8b5db6c209e9311ac8c6a44d3bf1856659 titled
"net: sched: rename qdisc_destroy() to qdisc_put()" part of the
functionality of qdisc_destroy() was moved into a (for linux-4.19.y)
new function qdisk_put(), and the previous calls to qdisc_destroy()
were changed to qdisk_put().
This made it similar to f.e. 5.10.y and current master.

There was one part of qdisc_destroy() not moved over to qdisc_put() and
that was the check for a NULL pointer, causing oopses.
(See upstream commit: 6efb971ba8edfbd80b666f29de12882852f095ae)
This patch fixes that.

Fixes: 92833e8b5db6c209e9311ac8c6a44d3bf1856659
Reported-by: Thorsten Glaser <tg@mirbsd.de>
Link: https://bugs.debian.org/1013299
Signed-off-by: Diederik de Haas <didi.debian@cknow.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/sched/sch_generic.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -970,8 +970,6 @@ static void qdisc_destroy(struct Qdisc *
 	const struct Qdisc_ops *ops;
 	struct sk_buff *skb, *tmp;
 
-	if (!qdisc)
-		return;
 	ops = qdisc->ops;
 
 #ifdef CONFIG_NET_SCHED
@@ -1003,6 +1001,9 @@ static void qdisc_destroy(struct Qdisc *
 
 void qdisc_put(struct Qdisc *qdisc)
 {
+	if (!qdisc)
+		return;
+
 	if (qdisc->flags & TCQ_F_BUILTIN ||
 	    !refcount_dec_and_test(&qdisc->refcnt))
 		return;