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net_sched: prevent NULL dereference if default qdisc setup failed

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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 22d95b5449249 ("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: 22d95b5449249 ("net_sched: add __rcu annotation to netdev->qdisc")
Signed-off-by: Pratyush Yadav <ptyadav@amazon.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Pratyush Yadav 2023-04-11 15:02:10 +02:00 committed by Greg Kroah-Hartman
parent 987f599fc5
commit c381527918
1 changed files with 1 additions and 0 deletions
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1
net/sched/sch_generic.c
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@ -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)