Commit 659b3b2c authored by Amery Hung's avatar Amery Hung Committed by Martin KaFai Lau
Browse files

bpf: net_sched: Fix bpf qdisc init prologue when set as default qdisc 



Allow .init to proceed if qdisc_lookup() returns NULL as it only happens
when called by qdisc_create_dflt() in mq/mqprio_init and the parent qdisc
has not been added to qdisc_hash yet. In qdisc_create(), the caller,
__tc_modify_qdisc(), would have made sure the parent qdisc already exist.

In addition, call qdisc_watchdog_init() whether .init succeeds or not to
prevent null-pointer dereference. In qdisc_create() and
qdisc_create_dflt(), if .init fails, .destroy will be called. As a
result, the destroy epilogue could call qdisc_watchdog_cancel() with an
uninitialized timer, causing null-pointer deference in hrtimer_cancel().

Fixes: c8240344 ("bpf: net_sched: Support implementation of Qdisc_ops in bpf")
Signed-off-by: default avatarAmery Hung <ameryhung@gmail.com>
Signed-off-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
parent 1b1f563a

net/sched/bpf_qdisc.c

+7 −5
Original line number Diff line number Diff line
@@ -234,18 +234,20 @@ __bpf_kfunc int bpf_qdisc_init_prologue(struct Qdisc *sch, 
	struct net_device *dev = qdisc_dev(sch);

	struct Qdisc *p;



	qdisc_watchdog_init(&q->watchdog, sch);



	if (sch->parent != TC_H_ROOT) {

		/* If qdisc_lookup() returns NULL, it means .init is called by

		 * qdisc_create_dflt() in mq/mqprio_init and the parent qdisc

		 * has not been added to qdisc_hash yet.

		 */

		p = qdisc_lookup(dev, TC_H_MAJ(sch->parent));

		if (!p)

			return -ENOENT;



		if (!(p->flags & TCQ_F_MQROOT)) {

		if (p && !(p->flags & TCQ_F_MQROOT)) {

			NL_SET_ERR_MSG(extack, "BPF qdisc only supported on root or mq");

			return -EINVAL;

		}

	}



	qdisc_watchdog_init(&q->watchdog, sch);

	return 0;

}