sfq: deadlock in error path (119b3d38) · Commits · 戴 / test

The change to allow divisor to be a parameter (in 2.6.38-rc1) commit introduced a possible deadlock caught by sparse. The scheduler tree lock was left locked in the case of an incorrect divisor value. Simplest fix is to move test outside of lock which also solves problem of partial update. Signed-off-by:

Stephen Hemminger <shemminger@vyatta.com> Acked-by:

Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/sched/sch_sfq.c

+5 −4

Original line number	Diff line number	Diff line
		@@ -491,17 +491,18 @@ static int sfq_change(struct Qdisc sch, struct nlattr opt)
		if (opt->nla_len < nla_attr_size(sizeof(*ctl)))
		return -EINVAL;

		if (ctl->divisor &&
		(!is_power_of_2(ctl->divisor) \|\| ctl->divisor > 65536))
		return -EINVAL;

		sch_tree_lock(sch);
		q->quantum = ctl->quantum ? : psched_mtu(qdisc_dev(sch));
		q->scaled_quantum = SFQ_ALLOT_SIZE(q->quantum);
		q->perturb_period = ctl->perturb_period * HZ;
		if (ctl->limit)
		q->limit = min_t(u32, ctl->limit, SFQ_DEPTH - 1);
		if (ctl->divisor) {
		if (!is_power_of_2(ctl->divisor) \|\| ctl->divisor > 65536)
		return -EINVAL;
		if (ctl->divisor)
		q->divisor = ctl->divisor;
		}
		qlen = sch->q.qlen;
		while (sch->q.qlen > q->limit)
		sfq_drop(sch);

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