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Commit c3815279 authored by Pratyush Yadav's avatar Pratyush Yadav Committed by Greg Kroah-Hartman
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net_sched: prevent NULL dereference if default qdisc setup failed 



If qdisc_create_dflt() fails, it returns NULL. With CONFIG_NET_SCHED
enabled, the check qdisc != &noop_qdisc passes and qdisc will be passed
to qdisc_hash_add(), which dereferences it.

This assignment was present in the upstream commit 5891cd5ec46c2
("net_sched: add __rcu annotation to netdev->qdisc") but was missed in
the backport 22d95b54 ("net_sched: add __rcu annotation to
netdev->qdisc"), perhaps due to merge conflicts.  dev->qdisc is
&noop_qdisc by default and if qdisc_create_dflt() fails, this assignment
will make sure qdisc == &noop_qdisc and no NULL dereference will take
place.

This bug was discovered and resolved using Coverity Static Analysis
Security Testing (SAST) by Synopsys, Inc.

Fixes: 22d95b54 ("net_sched: add __rcu annotation to netdev->qdisc")
Signed-off-by: default avatarPratyush Yadav <ptyadav@amazon.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 987f599f

net/sched/sch_generic.c

+1 −0
Original line number Diff line number Diff line
@@ -1116,6 +1116,7 @@ static void attach_default_qdiscs(struct net_device *dev) 
			qdisc->ops->attach(qdisc);

		}

	}

	qdisc = rtnl_dereference(dev->qdisc);



#ifdef CONFIG_NET_SCHED

	if (qdisc != &noop_qdisc)